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been a prudent mac, and by no means entirely under the influence of benevolent feelings and »elf-sacrifice; for, if he relieved bis contemperar)* musical clients from their entire dependence on TÎ. Stodart, he did not fail to take ont a patent for his invention, thereby making his musical clients dependent on himself. Perhaps one who diligently searches that mine of information, involuntary self-sacrifice, and, let me add, ■what the phrenologists term "acquisitiveness." yclept the Patent Records, might light on certain and sundry similar instances of that very moderate example of the manifestations of benevolence and self-sacrifice which was exhibited by Humphry Walton, whose pnrsuits, however selfish, were at least not open to the reproach of cruelty to animals, like those of his namesake and piscatorial predecessor, Isaac.
Robert Stodart patented the check for grand pianos in 1777. So slow are the race of pianoforte makers to adopt even proved improvements, that it was not until 1825 Messrs. Broadwood patented its application to square pianofortes. After this example of snail's progress, I should be a bold man, indeed, if I could expect any of my supposed improvements to come into use during this century; and I should be a very ancient fogy, indeed, were I to live to see the commencement of the next. We are told to cast our bread upon the waters, which is no donbt a moral duty—especially if we take reasonable care that it is bread, and not a Htoue that we cast; but, in some cases, it requires a great " many days" before it can be expected to reappear, and the old fogy don't expect " dis child" will live to see it.
The Harmonious Blacksmith.
SETTING AND FINDING THE POSITION OF ECCENTRICS.—TO "PAUL PRY."
[633 Let A, B, C, D, represent the end of the shaft, 10 in. diameter; let 6 in. be the travel of valve, which is the diameter of the inner circle, 1,2,3,4. Let the lap = 1 in., and the lead ¿th of an inch; add the lap and lead together, and set it off from X to О ; draw the line, 5,0,6. Aline drawn from the centre through points Vi and V* to tbe circumference is the centre of the keyway of the sheaves. The above is need for marine engines, and is quite proper. John W. Bedford.
SHORTHAND.  Sib,—" W." says that Pitman's system "is founded on philosophical principles." Most decidedly Lewie's is, and I to quote " W.'s " words) "its alphabet may truly be called the alphabet of nature, as it contains a symbol for each simple and distinct sound in our language." Lewis says in his book—" In shorthand the characters must be simple, and yet so perfectly distinct in their expression that no one character can be mistaken for another. Those characters that are most easily written and joined must he assumed to signify the letters or the sounds most frequently used, the more unmsual sounds being represented by the less simple characters." He explains his method of obtaining the characters, and points out the reasons for making use of those of certain forms, and rejecting others. With "W.'s" remarks on phonography I entirely agree; but Lewis's system is as much one of phonography as Pitman's—both systems are phonetic. Pitman's is the most well-known, owing to the existence of those periodicals enumerated by Mr. Cridland; they are the life-blood of the system, and were they to be discontinued, I believe it would fast lose its popularity. Mr. Cridland would doubtless have been as successful with Lewis's system as he has been with Pitman's, in a considerably shorter time. It does not at all follow that the most popular system is the best, Lewis's is comparatively unknown on account of its expense. Mr. Robinson admits that in Pitman's syetem a case may occur (though rarely) " where the grammatical construction of the sentence would not be a guide to the reader where thin and thick strokes wero not observed;"—as Lewis does not use thin and thick strokes, no such case can possibly occur in the uso of his system. Mr. Robinson goes on to say that the "prolific resources of phonography would provide for the emergency," but does not state how. This is rather vague. The last sentence in Mr. Cridland's letter is—to say the least— peculiarly worded.
ф Let us compare the two systems, taking the vowels first.—Pitman makes great use of the dot, and in his preface calls it one of the briefest signs. This is correct as regards space, but not time, for as much time is occupied in forming a dot as three or four letters, because of the utter impossibility of joining it to another character; he uses a thick dot to represent the sounds nk, a, e, as in alma, ape, eat, and a thin one for a, e, i, as in at, et, it, a short thick stroke for au, о, oo, as in all, ope, ooze, the same stroke thin for o, u, oo, as in on, up, full, each of these in three different positions ; also three small ticks, one of them at three different inclinations, all of them to be put in either one of two positions for the " compound vowels " i, oi, ow, as in ice, oil, owl, new, wine. "When a vowel is placed on the left hand *>ide of an upright or sloping letter, or above a horizontal one, it in to bo read before the consonant; and when on the right hand side of an upright or sloping letter or below a horizontal one, it is read after the consonant ;" there is thus a great chance of misplacing a vowel. Lewis is obviously right in stating that " when the writer is in haste, it is impossible to be very exact in the placing of the points, and the misplacing of cue will
deceive the reader more than the entire omission of it." It will be clearly seen from the above-quoted rule, that when compared with Lewis's system Pitman's has %ix positions for the vowels—viz., three on each side of the consonant—whereas in the former system it is not of the least consequence on which side of the consonant the vowel is placed. It is inserted as near its proper situation as convenient, otherwise its position is immaterial, whether top, bottom, or middle, above or below, right or left hand side; it is often more convenient to place a vowel on one side than on the other—this cannot be done in Pitman's. Lewis has five small distinct characters —all math' with the same facility as a dot—for the vowels, but none for the diphthongs, for which ho uses the characters representing the nearest vowel sound. I always employ a short vertical stroke to represent any diphthong not having the sound of a single vowel; not the least difficulty is experienced in reading the dictation a long time afterwards, although Pitman's "long," "short," and " compound " vowels are entirely avoided. It is simpler to insert two vowels, such as au in the Lowisiau system, ns the character» only have to be remembered, than one diphthong (mt for instance) in Pitman's, in which the petition aho has to be studied. Pitman ulso has four characters representing in different positions twelve double letters farmed with y and If as yah, poo, wau, Ac, "they are written heavy for Long and light for Short vowels, as in yate*, youth, iralk, Ac," Lewis has no such complex divisions. These characters as regards place, are »subject to the samo rules as the vowels, each class of which is subdivided into firtt, second, and third ¡nace vowels, according to their position. Pitman says "When a vowel comes between two consonants it impossible to write it either after the first or before th*second. To secure uniformity in the writing of phonographers, the following general rules are established :—First-place vowels are written after the first consonant. Second-place vowels are written after the first consonant when they are long; and before the second when they are ihort. Thirdplace vowels are written before the second consonant. The rule for a second-place short vowel does not apply when the second consonant is the circle £." Can there be nothing simpler than all this?
Let us now compare the consonants and peculiarities of the two systems.
Pitman uses eighteen dißerent signs to represent twenty-four consonants or combinations of consonants. Eleven of these are nsed twice—thick and thin— mostly representing similar sounds, but г and If, I and y, ng and n, have tbe same characters respectively, thick and thin, although greatly differing in sound. Five consonants have each two different signs, and h has three different signs.
Lewis has seventeen different signs to represent seventeen consonants, and ten other signs to represent ten double consonants of frequent occurrence, such as Ы, br, gl, Ac. Some of the signs are the same in both systems, but they do not represent the same letters. Pitman gives the sound Zh a character; how often is it required? He has also given ng a character; these letters mostly occur in the terminations ang, ong, ing, or и n g, for which Lewis uses the characters for the vowelsa,
0, i, u, placing them in the most convenient position below and at tbe end of the word; it is seldom necessary to write these terminations in shorthand. The prefix eon or com is expressed in Pitman's system by a light dot at the comencemeut of a word, and the affix ing by a light dot at the end of a word; there is no short distinct method of exprès-ing any other prefix or affix in this system. Lewis uses ten signs representing twenty prefixes, and eight other signs representing nineteen affixes, so that in many long words the primary and terminating syllables may each be written with a single stroko of the pen—the affixes are always joined to tbe word. Pitman writes the aspirate A either by a small dot prefixed to the vowel sign—thus bringing two dote close together ;—or by either of tbe two other characters. He also uses a little tick at the commencement of the word for the £anie purpose. Lewis uses one simple character, which Is written in much less time than the dot, and is all that is requisite. In Pitman's system л is added to a letter by a "final hook on the left-hand side of a descending straight letter, or following the direction of a curved letter ;" I andr may be added to other letters by an initio Í hook, and»' before
1, as in ir< 11, may be also thus expressed. *' When a thin consonant is made half length, that is, one half of its usual size, it acquires the additional power of t, and a thick letter halved expresses rf. The letters, n, m, I, r, are made half length to express the addition of t, and are then thickened to express d. When a verb ends in t, the past tense (if formed by adding the syllable ed) is written by shortening t, A vowel placed after a halfsized consonant is read before the added Utter." Why all this complication? Lewis has nothing of the sort.
Lewis has'eight "key symbols," which are extremely useful—one stands for 4c., another for viz.—one points out where a proper name occurs—another where there is an omission, 4c. Pitman has nothing corresponding to these. Lewis uses a small long-hand q placed after a question, for a note of interrogation. Pitman has a double sign, to make which—as given in the *' Teacher "—the pen must be lifted twice t It must also be placed before the question, which is obviously not so convenient as after. He represents Twenty-four small words by his *' grammalogues or letter-words," and the word that "by the shortened sign for th." Lewis represents Fifty-four by his "definite contractions for small words," and Fifty-four other words of frequent occurrence by his ticked characters, which are merely the symbols for the consonants and double consonants, with the addition of a small tiek. There is thus not the slightest difficulty in remembering them. A very useful feature in Lewis's system is the
possession of figures, which are formed from part* ct the long-hand figures. They may be written separa or joined. I could point out other advanuêe* a Lewis's system, but have already occupied too mace space. Many advocates of Pitman's system will *a» :.; is "simplicity itself!" and that any one who ежпл;ш aste г it is a fool. Perhaps so; but what reason i there to burden one's mind with its above-men tluuH perfectly unnecessary rules and régulation», wbrii * much simpler and yet more complete system is equal to it in rapidity—if not superior? It may W all very *• II to say this letter proves the completeness of retourixof Pitmau's system over the Lewisian or any otlwr system; but it must be remembered that this но-са!!-completeness, with its concomitant rules, may :. carried to any extent, and render the sybtem vnz more complicated. I have remarked on every fe*.tur' of both systems, and have quoted from the elcwiil: edition of "Pitman's Phonographic Teacher," to a«4i mia-statement*; but should there be any above, I hop to be corrected, a* my only object is to direct "uittíjí to the best system, und cause him to avoid all wliici. ¡ike this, are as ''Mac D" remarks "complex шл. unsatisfactory." Diydeu writes, "to ignurance all i-, wit that is abusive." I hope no one will favour me with wit of this kind by way of an answer.
In conclusion, let me ask—Does any one of your correspondents know Lewis's system? If so, will ht be kind enough to point out any complexity in it?
Frank W. Grixrson.
THE CULTURE OF THE MUSHROOM.
 Sir,—"J. T. P.", 4250, p. 383, should first procure a quantity of horse droppings, free from straw and stones, and pile them into a heap, which inust be patted down firmly, and allowed to heat; when well warmed all through it should be shaken out and again made into a hAip, changing the sides into the middle. After two or three of these "heatings" the dung will become sweet, which may be known by placing a piece of glass on the heap, and if the water that condenses on it is clear, the material will be fit to form into a bed. The bed may be of almost any dimensions, but a rounded form is best, as giving a greater surface from which to gather the mushrooms; some say ¿ft. broad by 3ft. thick, rounded off, others lain, or 'Jit. thick, alopim? to nothing. It must be put together rather firmly, and should be neither too hot nor too dry. In a few day« the heap will in all probability heat violently, and when the temperature has fallen to 70 or 75 Fabr., will be about the best time to put in th« spawn. After the insertion of the spawn, which should be broken into pieces the size of hen's eggs, and placed in bolea about V in. apart, the surface of the bed should be patted together with a spade, and then covered with a layer of straw about 6 in. thick. In about ten or twelve days examine the bed, and if you do not see tbe thin white nbunents of the mycelium spreading out from the lumps of »pawn it is certain that the heat is not sufficient, or the spawn is bad. If the former the whole bed had better be pulled to pieces and remade ; if the latter, procure fresh spawn, which should be placed in different holes to the first. But if the spawn has begun to run you may procoed to cover the bed with an inch or an inch and a half of good loam, which should be patted close and gently watered, and the covering restored. This form of bed will do for a cellar, outhouse, cupboard, or the open air, but if the latter it should tie covered with straw at least a foot in tliickness. When the mushrooms are gathered a little earth should be placed in the holes whence they are taken. As to the kind of spawn to use, I think tlie French is undoubtedly the best, as what is generally bought at tho seedsmen's is too hard and dry, whereas the French is in thin Hakes, cut from heaps full of mycelium. Droppings obtained from a mill track, invariably contain spawn, and have only to be placed in small heaps to produce abundant crops of mushrooms. In the neighbourhood of Paris the^e delicious fungi are grown in caves either underground or e\cavated in the side of a hill, and even in deserted slate and stone quarries, as atFrëpillon, Méry-sur-Oise, where at one time no fewer than '21 miles of beds were in full bearing. Of course in these comparatively warm subterranean caves a bed does not require any covering, but yields abundant crops for No>, three, and even four months.
There is, in fact, scarcely any kind of waste Fpac«ï where mushrooms might not be grown—in pots and old tubs under the stage of greenhouses, on shelves in stables, indeed, in any situation where sufficient dung can be placed to heat, or merely enough for the spawn to spread if artificially warmed. Haul Rymka.
[GT>] Sir,—I think there is some truth in the old adage, "experience makes fools wise."
After thirty years spent in tbe manufacture, distribution, and the testing of coal gas, I may pretend to possess some information on this subject.
I have, at the present time, to superintend tho distribution and consumption of gas to the amount of ilf.,000 per annum; and one of my chief duties is te> see that the largest amount of light possible is obtained from a limited consumption of gae.
I would at once adopt the mode of improving common coal gas by carburization, if I bad the smallest hope of obtaining any real lasting benefit from it.
"C. D. C," in his letter (p. 354) says, respecting my answer to query 3810, "That I am certainly not well informed upon the real facts and principles involved, and it would have been better had I given my opinions, and then invited thoso of some of the talented chemists who have contributed such valuable articles in the pages of the English Mechanic. I inust confess that I am not a talented chemist; and it tuny ha also true that " C. D. C." is right in his remark that I know nothing about the curburization of gas. Be thiii a- it may, I will now add ноте of the facts I do know respecting improving common coal gas by the mean» of curburization. For nearly two years the process of curburization was tried in the city of London public lumps, under, I believe, the direction and inspection of Dr. Lethebv, and yet Whs abandoned, and huit not again been adopted. Great economy, with increase- of light, was at that time promised, according to the theory aud estimate of the projectors.
To ensure economy in the consumption of gas, the ordinary barkers, consuming live feet per hour, were changed to those which would only censuine three feet per hour. Of course the gas company's bill was materially diminished. Bat what about the increase of light ? very often the streets of the City of London were in comparative darkness, and so loud became the complaints of the public that the authorities were compelled to order the removal of the carburizing apparatus and to restore the ordinary nve-feet-per-hour burners.
I am well acquainted with the fact that within the last three or four years the principle of curburization has been revived with all the pretensions to originality. Many fresh patents have been taken out. The apparatus now in use no doubt are superior to those formerly employed. But the main difficulties still exist,—namely, tbe irregular evaporation of the liquid, and consequently the uncertainty of the light obtained from gas passing through the vapours of the carburizing liquids.
The following is on account of an experiment made by an able chemist in order to ascertain the rate of evaporation of liquid hydrocarbon. The material chosen was the spirit of petroleum, as light as it could be procured, being about '700 specific gravity. 31b. of the above were placed into a suitable vessel in snch a manner as to expose a largo surface for evaporation, and on passing atmospheric air there-through by means of a motive-power meter, a very large and rich dame, giving off abundance of smoke, was the result. This at the commencement, when adjusted to aft. per hour, gave a light equal to sixteen candles, but speedily the name become perceptibly less; in a short tune it was diminished to a remarkable extent. After twenty-six hours merely a blue light was obtained, and at the end of forty-eight hours no dame whatever existed, as all the volatile constituents at the temperature hod evaporated. On re-weighing the residue, barely one-half of the total quantity had been avouable. This clearly demonstrated how easily people may be deceived by a carefully prepared experiment, for at the commencement the air was so highly charged with carbon as to occasion the greatest surprise; but as this was of such short duration on account of the very »mall quantity of the highly volatile material, the experiment was very deceptive, and the process of carbonizing the air utterly useless. In conclusion I may add, my former remarks in No. *2t>9, page 2ti0, were not xuude without woU considering the subject, and as I am in no way interested in any gas company, or the manu facture of gas, my object is not to make large gas hills.
I have one of Evans's photometers with all other accessories for the analysis of coal gas at my command. Very recently I tested a new corburetting apparatus, but failed to realize anything like 5U per cent, saving. 20 to '25 per cent was the very highest average I could obtain. Against this there remains the uncertainty of the light obtained from the corburetting process, the expense of apparatus and naphtha, the attention required, and last of all, and not the least objection, the dangers to be guarded against in the use of highly úiüammable petroleum. Every gas consumer is not a practical chemist. L. M.
[G7] Sib,—Knowing your readiness to assist inventors to make known their inventions to the British public, I venture to send you a few linos concerning a telegraphic invention which is quite highly spoken of this sido; it is an improvement in relay magnets, invented by William Smith, of Cincinnati. It is not easy to describo without drawings, aud they are not to hand, but perhaps your readers will understand when I say Hint the connections of the relay are so arranged that the main circuit is divided, half passing through each helix, and coming together again on the opposite side. The advantage of this arrangement appears to me to be that the resistance is reduced to one-fourth,whilst each of the two helices will exert its magnetic influence, in conjunction with the other, and the soft iron armatures will be acted upou as usual. The arrangement is claimed to lie a considerable improvement, aud the inventor will be glad to give particulars. H. J. C.
Washington, June 21.
PROF. PtUTCHARD AND MR. PROCTOR.
Io'.si Sib,—It will be in your remembrance that a day or so after sending my letter headed "unfair criticism," I wrote, begging you to remove all but the defensive portions of the letter. Contrary to my expectation, the letter had already been sent to press at that time.
I wish now to point out that I may have been over hasty in attributing wilful unfairness to Prof. Pritchard. He may have muconceived (not misinterpreted) the sense and spirit of my work. In this case, an apology wiU be due to him, which I shall be most ready to make.
The case is now reduced to a very simphi issue. I
have submitted to Prof. Pr-tehard what I take exception to in his review, pointing out where aud how he has misconceived my meaning. If he admits that my objections are valid, my obvious duty is to admit that I have unjustly charged him with unfairness. If he maintains the justice of his criticism, in the face of the evidence. I shall have no course left open to me but to maintain the justice of my counter criticism.
I need hardly say that I would infinitely prefer to resume my belief in the wisdom and justice of an astronomer whom I have for many years regarded with sincere respect and admiration.
Richabd A. Phoctob.
THE SYMBOL ».
 Sir,—In answer to "Gimel," both the statements in "Todhunter's Trigonometry" are correct. The symbol w is often need to represent the ratio, (3*14150'—) between the circumference and the diameter of a circle; and the circular measure of two right angles is equal to 8*14159 .. . Since the technical expression "circular measure" is applied to that mode of measuring angles in which the unit is the angle whose arc equals the radius, it foUowe necessarily that the circular measure of two right angles will be represented by the ratio of the arc of а semicircle to the radius, and this is, of course, equal to the ratio of the circumference to the diameter—a ratio invariably expressed, as Todhunter remarks, by the symbol ж.
Richard A. Proctob.
MR. LOCKYER AND MR. PROCTOR.
 Sir,—In a note to Nature, signed "Editor," Mr. Lockyer usserts his view of the corona is not what I state it to be; and he proceeds to describe his view precisely as I have described it in "Other Worlds than Ours." He goes on to remark that I have misrepresented Dr. Gould's statements, simply because I have indicated a different interpretation than that which Dr. Gould has given. It happens, as I have but just found out, that Dr. Curtis and Professor Harkness (both mathematicians of repute), indicate their nonacceptance of the interpretation put by Dr. Gould on their common labours. Both of them also indicate precisely the same reasons for rejecting the atmospheric glare theory of the corona, which I have put forward.
But the strangest port of Mr. Lockver's note is that in which he remarks that, "surely Mr. Proctor is old enough (nie) to see that by attempting to evolve the secrets of the universe out of the depths of his moral consciousness, he simply makes himself ridiculous." In this way he describes reasoning of mine founded on observation, and strictly mathematical in its character. Probably he has not considered how large a share of modern astronomy has been evolved this way. Copernicus, and Kepler, and Newton, did not themselves observe the facts they reasoned upon, nor would Neptune have been discovered had Leverrier and Adams been unwilling to apply mathematical reasoning to the problem.
Mr. Lockyer has not always exhibited such contempt for mathematical reasoning. I once "evolved from the depths of my moral consciousness," tho fact that in certain parts of Saturn the sun is concealed by the rings of the planet for such and such intervals of time. This remark, so far from seeming ridiculous to Mr. Lockyer, struck him as worth appropriating, and accordingly it appears in his "Elementary Lessons of Astronomy," with nothing to show that Mr. Lockyer himself had not discovered it, unless the extent of his acquaintance with mathematics be supposed too clearly indicated throughout the book for any one to credit such a result to him. Cousidering that in this and other instances Mr. Lockyer has been willing to profit by (if not to take credit for), my mathematical examination of observed relations, his suddenly discovering that they are ridiculous, when they happen to oppose his theories, looks more than suspicious.
Richard A. Proctor.
A USEFUL TOOL FOR TREATING INCLINED OR LEVEL SURFACES.
 Sir,—I submit to your readers a useful little tool for treating inclined or level surfaces. It will be fonnd useful at lathe or planing machine, in setting the work at various angles. It consists of a good parallel strip of steel, A, upon which is erected a cir
cular brass plate, B, with indices marked on it, through the centre of which passes a small screw pin, upon which the needle, C, freely revolves.
NATURAL SCIENCE IN MILITARY
[72J Sir,—In connection with the subject of Natural Science in Military Edncation treated of in a letter (signed "T. R. J.") lately in Scientific Opinion, permit me to offer the following observations :—
Eight years ago Colonel Dixon, R.A., treating of Military Edncation, wrote thus—"In fact it must march with the times and advance at the same rate as general education aud intelligence advance." Abont that time so much greater attention was given to military education (or, rather, the high value of scientifically educated officers was so much more fully and honestly recognized by the authorities) that staff appointments were no longer given haphazard, according to caprice, favour, aud family-ties, but officers specially educated were only chosen, and the Staff College itself was built, with a laboratory-, &c., and the students placed on a better footing than before. Awakened interest in the cadet department of tho Royal Military College, Sandhurst, hod also about that time led the authorities to modify the plans and subjects of studies there in accordance with modern requirements. Classics hod disappeared from the curriculum ; and geology and chemistry (natural philosophy and physics) had been put within the reach of those who wished to follow out their taste for natural science, and of those who recognized its value in every-day life.
This reaction, on the part of the military rulers, from former carelessness for science and neglect of educated officers, produced good results. I learn that fourteen hundred gentleman cadets have gone out into the world with some knowledge of the natural and experimental sciences, often grounded on a native taste, which would otherwise have been starved, or-on previous teaching, which would hare borne but little fruit. Of two hundred and fifty staff officers I understand that upwards of fifty have studied geology, and others chemistry, practically and theoretically. The other branches of learning in cither college have, of course, been mathematics, military arts and science (the hitter founded chiefly on geometry and the science of numbers), drawing, some modern languages, and military history, in greater or less degrees.
Some old-fashioned minds, brought up in the belief that English gentlemen are under any circumstances equal to the exigencies of military service, whether commissioned from the nursery, school-room, billiard-room, or hunting-field, were reluctant to allow geology and physics a part in the general training of military men. Had they not hitherto successfully blunder¿.чЬш, pluck, persistency, and common sense currying them through battles, campaigns, and administrations, with such losses, mishaps, und entanglement* as were considered inevitable, aud gloriously smothered by accepted triumphs?
The practical advantages that have accrued to those who have studied natural science at the Military College will as yet have been chieäy found in healthy employment of body and mind, und in the satisfaction of intelligent views of natural phenomena. That military men appreciate und relish this source of useful pleasnre is well known to students of Indian, African, and West Indian geology, which they have largely helped to elucidate. Sir Charles Napier was not content to conquer the Beloochees; he insisted on having a geological report on the structure and mineral condition of their country, and he had it well made by a gallant officer in spite of difficulties. Lately the Geological Magazine welcomed an artillery officer as adding to our knowledge of the geological history of St. Helena, and increasing the bounds and influence of natural science. Lastly, General Portlock, Colonel Dixon, and Captain Huttou have urged their brother officers to cultivate geology aud allied branches of science as of practical value in many ways. Indeed, one of them says, " As geology is the most useful of all the sciences to a soldier, so is a soldier's profession the one of all others best adapted for its study."
To say nothing of the great advantages commanded by a military officer, in having a knowledge of the nature of things, in being acquainted with the conditions, actions, and reactions of air, water, and earth— of heat, magnetism, electricity, &*., surely the man who has to fight nature at all point*, in all parts of the globe, on all occasions, and that not for himself alono, but ш tho interests—the vital interests probably —of hi« company, his regiment, or army, and of the nation itself, requires more intimate knowledge of physical geography and geology, of mineralogy and natural history, than of high mathematics and ancient classics. He requires an educated eye and mind, not mero у seeing the features of ground, hut recognizing their inclining, their persistence or limitation, and their indications of internal structure, and not merely amusing his art faculties with light, shades, and tints of landscape, but reading the. character of beach, cliff, hill-side, and mountain tops, valley, gorge and pas*, spring, marsh, lake, river, and ford, so as to be able to master difficulties, uvoid mishaps, und benefit by cireunistancos. He requires, too, a ready hand for other implement» besides the sword. He must hammer the rocks, and study their characters at hand with the magnifier, as well as dis«ru their nature from afar with hie field glass. How else can ho know what stone to choose for road motal, for instance ? and without the blowpipe he can scarcely determine the useful mineral or valuable ore that may turn up along his ronte.
Such geological knowledge has been of late years taught at the Royal Military College, but the recently published Reporto!' the Royal Commission on Military Education recommends that the cadets should not be taught natural science, but be allowed to study classics instead, because (it states! the large public schools, from which it is thought desirable that cadets should come, do not teach physical science, but, teaching classics and mathematics, give such youths the limited means of taking a place in competitions by those alone. Few cadets, however, it appears, join the College from the large public schools, and those chiefly from Cheltenham, where a "Modern Department" exists in vigorous life ; and, whatever tho desiderated plnck, dash, and wealth of public schoolboys may be, surely the more liberally educated students from other sources will beat them ont of the field of competition, whatever limitation may be set to the snbjects of study. But not only are there many schools and colleges that have instituted a "Modern Department" of science and literature [and that, be it remembered, largely in consequence of the improvements in military education requiring candidates with wider and sounder knowledge), but the large public schools have of themselves begun to add physics, chemistry, and natural history to their teaching. *
Thns the Royal Commission proposes a retrograde movement in national education, puts aside tho study of a science valuable to the military man, and slurs the scientific character of the age.
The report certainly suggests that at the Staff College, geology be still taught, but as au art (if so be it could), "practical and without mineralogy," a play without a plot, a biography without a life, "cram" without meaning, facts without explanation. This, too, the report recommends to be taught by the chemist, already occupied with the arts of photography, telegraphy, torpedo - making, 4c, and with such philosophic chemistry as time will allow, and the tastes of his students will require. Indeed on the proposed system the staff officer will have no obligatory study of pure science of any kind, and science in the lino and staff of tho British army will be officially reduced to schoolboy physics, amateur philosophy, and rule of thumb. Why should this be? Surely there are more schoolboys and candidates for the cadetship that have a taste for natural philosophy and geology than for classics. Let their tastes be cultivated. Surely tho scientific culturo of officers should not be neglected because some know little of its real value, or fear that the Staff College may become "a sort of fool's paradise of abstract learning and science "—(Lord de Ros in the Report). At all events, they leave science to take care of itself without any honours being offered, or even credit given to its student, who is tempted to leave it for work that places him high on tho college list. Surely the cry of "too much work " is not true; the intellectual effort of military studies is not iutru -<■. There may be too many subjects before the student at a time. If it be so, let a good selection be made for individuals. Let means be provided for the cultivation of strong natural tastes and good acquirements, let special studies be fostered, and there will be less complaint of idleness in the cadet, and of superficial knowledge in the officer. Such good results, however, can scarcely be expected from a Royal Commission (however earnest its members may be) that comprises no representatives of natural science, and has not asked for any information from experts or authorities in tach matters. Mem.
THE FLUTE AND FLUTE-PLAYING.
 Sib,—I have felt much interest in the letters which have appeared in your most valuable journal from Messrs. Leftwich, " Sable," and "Orion" upon flutes; and with your permission I now venture to offer a few remarks upon that subject myself; and in the first place I beg to state, that although, as a Loudon professor, I have had flutes from most of the principal firms, yet I have no business connection with any one in particular. I shall not enter into the question whether the Boehm system is better than any other; no doubt it has some advantages; but when *' Orion " каун " that there are many passages which cannot be played in a creditable manner on the old flute," I cannot help thinking that his acquaintance with flu to players must be limited, and I would recommend him to examine the fantasias of Nicholson, Frisch, Knhlau, and others: ho will there find difficulties which were played on the old eight-keyed flute, and in the hands of the many fine players whom we have had they were :i either " struggled over nor botched."
There are many professors now living who remember the late Charles Nicholson, and they one and all concur in saying that his playing surpassed all that they had heard before or have heard since. I had the pleasure of being a pupil of the late R. S. Platten, and at that time he play edon the eight-keyed finto.as made byMessrs. Rudall £ Rose, and in my opinion he never played better than he did then, for it seemed to me as if ditliculties were unknown to him ; and who is there in the musical world who does not remember the charming solo playing of the late Mr. Richardson, the bird-like quality of the tone, the perfect execution, and the correct intonation in his hands of Prow su's Auto? I could name a host of others of the past, but I will come to the present.
Did " Orion " over hear of Mr. Alfred Wells, who has been the solo flute in that magnificent baud of the Crystal Palace for about fourteen years. In that orchestra music of the most difficult character is executed in the most splendid manner, and yet the gentleman I have named above plays on the poor old, but much abused, eight-keyed flute, and I do not think that any ono will accuse him of" botching or struggling" over the passages, be they ever so difficult, whilst in tone and intonation I do not think it would be any easy matter to surpass him.
With regard to the old flute being out of tune, I am willing to admit that in its construction it is imperfect; but in the hands of a good player, with a correct ear, its imperfections disappear, whilst in the hands of an indifferent performer even an instrument perfect in its construction (if such a thing exists) can be, and very often is, played out of tune.
It is the instrumentalist more than the instrument that must be in tune.
I myself play on Siccama's flute, and have done since 1847 ; in fact I was the first professor who adopted it; and as my instrument is one of the first models made by the above gentleman, I prefer it to any other. It is simple in its construction, very well in tune, and a good tone, and quite loud enough fur any flute (for I think, with one of our great conductors, that one does not want to play the trombone on the Ante), and the fingering of the old flute, with a few exceptions, can be ncd, whilst there are also other fingerings which simplify the execution of certain passages. The Siccama flute is now made and sold by Messrs. С happe H A Co., and by Mr. Hanson.
I have no doubt that on the Carte Iioehin flute many passages are much moro easily fingered than on the old flute; but there always appears to me to be a great difficulty to overcome in acquiring the use of the open keys for the thumb of the left hand; and to talk of every passage being easy on those instruments is simply a mistake.
With respect to the price charged bv Messrs. Rudall, Rose, & Carte for their flutes, which " Orion " thinks is high, I do not think that it is possible for such exquisite workmanship to be executed for a smaller sum,
With respect to the flute invented by tho late Mr. Clinton, I never could see any advantage in it over the Siccama Ante, and it is more complicated in its mechanism.
As I dislike writing under an assumed name, I beg to remain,
Henry Chapman, Professor of the Flute.
THE SUN'S PARALLAX.
 Sir,—" Veritas" asks me, on pago :¡08, whether an angle at tho centre of a circle is a measure of an arc of that circle. If the radins be known it certainly is so. His second question is, " Is tho taugent an arc of that circle?" I do not know why he asks this, but, of course, the answer is "No." I cannot imagine that any one with any knowledge of trigonometry can want a proof of such a self-evident fact as that angles are not proportionate to their tangents.
Having answered his questions, may I ask him whether he really intended to write the following:—"And in every* case the sine of any angle is to unity as the cosine of the same angle is to the tangent of that angle." Let us follow this out and see to what it leads. We have
sin A: 1 :: cos A : tan A
.'. cos A = siu A. tau A
cos a .•. cosí A = ein2 A or cos A = sin A which is absnrd.
I will now «how him what I meant in the letter to which he refers. Let E be the centre of thu earth, V
that of Venus, and S that of tho sun. Let P be a point on the earth's surface, such that P E V = 1)0°; and let all the lines bo in the same plane. Then E V = distance of Venus = E P cot. P V E, and E S = distance of the sun = E P cot. P S E ; therefore the distance of the sun : distance of Venus : : E P cot. P S E : E P cot. P V E, or, as cot. P S E : cot. P V E; therefore tho distances of theso bodies, (and of any others) are proportional, not inversely to their respective parallaxes, but directly to the cotangents of their parallaxes, or inversely to the tangents of those angles. I am unable to test this result numerically, because I have no tablee calculated to so
small a quantity as one second, much less to a fraction of one; but I am confident that the parallax thu» found will bo that which is generally accepted to bo true. Hugo.
AN ENGLISH MECHANIC COLONY—HONEY-BEE
 Sir,—I am glad to find that the thought expressed by your correspondent "Alexandra," page 880. exists in more minds than one. I have long expressed the belief that our present system (?) of emigration i-9 not only cureless and thriftless, but most reprehensible. The harum-scarum way in which our population is now leaving us, each one to shift for himself—on armv (in numbers) all pioneers, without organization or concerted design—indicates a singular want of providence and forethought on the part of our legislators.
Where shall I emigrate? what shall I be required to do? what shall I want when I get there? areqnestion* which meet the eye in every popular publication, and advisers are as numerous as their interests are diverse and multiplied. Since we profess to be so fond of what is natural, let us take Ru example from the crowded hive. The honey-bee emigration is organized lief orehand, the note of preparation is heard long in advance, and they go, carrying with them the habits and discipline of their birthplace, and adopt a new home under the security of mutual aid and protection afforded by the aggregation of trained industry and preconcerted design. At present the energies of our emigrants are often wasted by being scattered, and individual toil i* exhausted in hopeless conflict with difficulties easy of removal by conjoined assistance.
Our emigration parties should be arranged long before starting, and should as far as possible represent a slice of the mother country, or at least of all the useful and economic departments of it. For example, «orne block of laud with sea or river frontage, say, five, ten. or fifty miles square, in surely still attainable in our colonial territories, and by government sanction or possibly charter. Such a place—the new colony of *' Alexandra" for instance—is deemed to be available for settlers, and is allotted to a council formed of emigrants, constituted before leaving England. That council would then invite co-operation. Persons of tastes and habits opposed to the tone of their leaders woold of course not offer themselves. Tory leaders, for instance, would hardly get Radicals to associate themselves; teetotallers would join teetotallers ; high church leaders would only get those of tho same class of thought; so that those associated would be for the most part of congenial habits and dispositions. The position of life of those fitted for tho colony would Ы another basis for selection. It would not do to bave a preponderance of one or two chusos: a majority of shoemakers or of blacksmiths, or of any other calling, would be guarded against. The parson, the doctor, the lawyer, the magistrate, the police, Ac., Ac., should all be subject to selection beforehand. And all this could be done without ignoring the rights of property or invading individual claims, the one to 100 acres, the other to 1,000, as his means might l»e. The great evil of male emigration, to the exclusion of families, and which tends now so largely to demoralization both at home and abroad, would be obviated, as it would assume the possibility of families emigrating in their entirety, and not the adult males only as now. It is a lamentable fact, and one greatly damaging to the welfare and interests of the community, that, large as is already the excess of females in England, it is yearly becoming greater through the excessive emigration of males. What a tale of endurance and misery does this one fact unfold, which would all be obviated by ** honeybee emigration," that is in " swarms," not in single and solitary departures, which the present pioneering necessities encourage or demand!
To illustrate once more. Let us suppose that a dozen earnest men—intending emigrauts—firstly, by correspondence and agreement among themselves, apply to the Colonial Secretary for such a grant of land as I have described, and having obtained it, publicly announce their forthcoming departure this day twelve months, who can doubt that all the essential requirements of a village would at once be forthcoming. A little slice of England—a true hive of industry—would at once establish itself, without that dreary, heart-sickening despair which must sometimes paralyze the efforts of isolated inhabitants in a new and thinlypeopled country. Joking a lady about the new plan, I was told that if the first swarm was to consist of 1,000> I need only trouble myself abont 500, for the " better half" would be forthcoming at once, aye, and with money too.
For the sake of tho female population of this country I rejoice to believe that they would willingly join in such an assured and organized movement; and, if nothing else prompted the wish to promote it, regard for them is to me avowedly an incentive to bring it under notice. Tho question is Arider and deeper than at first appears. If, from the daily increasing disparity in numlH?rs between the two sexes, marriage is simply impossible to tens of thousands of the women of this land, and if amongst those who are to be so blessed the larger proportion await that happiness in obedience to civilized requirements which discourage early marriages, let us, by a system of emigration in which they may join, help to place them in positions in which early marriage is both wise and honourable—where, in fact, it may bo their happiness to obey the Divine injunction, "Increase and multiply, and replenish the earth and subdue it." M. D.
IRON IN BATTERIES.  Sir,—I sec that *' Sigma" has somewhat modified his previous opinion as to the use of iron in batteries. Abrnit three year* ago, owing to the difficulty I experienced in getting thick rolled zinc, I tried iron as a substitute, and obtained te in Its so unexpectedly Rood, that I have continued tonte it ever since. My first triait* were with cast iron plates, the battery arrangement being the same as Groves*—viz., platinum with nitric acid, and the cast iron in solution of salt; thie gives very good action for a few hours, bot at last the ca4t iron becomes covered with a plombagine deposit which stops* the current until it is entirely removed. Latterly I hare used wrought iron either in plain water, weakly ocidtir. laU-d water, or solution of salt. Of the three I think th* litter gives* the strongest current,'; but there are -ошв peculiarities about the behaviour of iron in this solution, wliicU require to \w studied. Frequently, but not always, the iron plates, after being taken out of the saline, solution and allowed to dry, will refus« to act, and continue iuactive until dipped in an acid solution for a short time. The same thing does not happen when the iron is used with acid, and for this reason I give the preference to the use of weak acid solution, or else to au arrangement of saline and acid solution in each alternate cell, chuugiug the plates from the one cell to the other after eaeh removal.
It appears to ma that the nitrous acid fames are in this battery absorbed to a great extent by the iron solution in the outer cell, ав I do not find them affect the Atmosphere of the room much. Will "Sigma "say whether this is likely to be the ease. I am uudor the impression that nitrous acid Ras* has a strong affinity for iron solutions. If I am right it could probably be aot rid of altogether by closing up the porous ceil and leading it by a bent pipe into the outer solution. The first elfect of the battery action appears to be to give a blue colour to the nitric acid. What is the cause of this? la it owing to tho formation of forro-cyanuret '.' I had overlooked the description of Slater's battery until "Sigma's" last paper called my attention toit. His description, however, differs considerably from that given by"D. F. K.,"page 132. in which the chief novelty appears to be the nao of nitrates in the outer cell with tho iron, nitric acid being used as usual with the carbon in the porous cell ; and it is claimed that by adding nitrates und nitric acid to each respectively in proportion to the work done, the constancy of tho battery can be maintained. "Sigma's " description differs materially from this, the nitrates being used exclusively in the inner cell instead of ^nitric acid, which is no novelty. I have failed altogether to keep my batteries constant by adding nitrates and other oxygenous salts to the exhausted solution in the poro as cell. Even fresh nitric acid has but little effect unless the old liqnor is completely emptied out of it. I attribute this to tho endosmosic action which converts both the inner and outor solutions into a thick black liquid. Even plain water becomes equally black after a time, and at first sight it appears to me that the u«a of nitrates in the outer cell is a step in tho right direction with a view to constancy. Altogether, having regard to the cheapness of iron as compared with zinc, I am inclined to think that it has not received as much attention as a positive element as it deserves.
"Sigma V great courtesy iu replying to enquiries, not always very reasonable, cannot be too often acknowJedged by the readers of the English Mkchanic. July 4. Thomas С Haines.
(771 Sir,—I can scarcely imagine ft more perplexing position tu be placed in than that of " Cotton Clerk, and having been in a somewhat similar one, can fully sympathize with him. Where U he tu go 'Í One lauds South America, but others come forward who, agreeing with him in some things, still relate others equally true that would seem to put emigration to that place out of the question. Australia, New Zealand, and Natal find supporter?, and although nothing is said against climate in these cases, distance is urged as an objection. The Western States of America seem to find most supporters, and to judge by what some oí them say, it is n very laud of milk and honey. But these firm advocates of western life do not tell us that, in addition to Indians, who make periodical forays into tho settlements, murdering and scalping the poor emigrants, there is the continual pistoling, gouging, lynching, and cheating of the civilised white Indians tu contend with. Not a word i* said for Canada, One regards it as afilie ted with a severe winter, but does not tell u-> that most of the western states are so afflicted : and that on the unsheltered prairies uf the west is almost unbearable. Hot summers and cold winters are not peculiar to Canada, but are the rule in North America generally, the States as well as British possessions, these seasons being far more marked there than in England. I was glad to sec the lettc-r of "F.R.G.S." in support of tho British colonies, and I think he is on the whole right.
Still, to those who are not lovers of the sea, a voyage to Australia is a serious consideration. So if those of your correspondents who contemplate emigration are not good sailors, or if they don't like the idea of eating roast monkey while they "themselves are being roasted under a tropical sun in South America, or if Indians, red and white, and border ruffians aro an objection, why not turn their thoughts to Canada. Land may be bought there at very cheap rates, near markets, wild or cleared, and free grants oí ¿00 acres may easily be procured in available situations, the terms being in either case nearly the same—an obligation to clear a certain portion of your allotment In a given timo. That part of the bargain completed, the settlor becomes undisputed owner of the soil. This is nat, a-, some think, a life-long work, but cau by industry be accomplished in a short time, and sufficient in a few years may bo brought into cultivation to make any man of moderate expectations well off. There is not much difference in quality between the free grant and other lands—you may buy nearer a market. Easy access to markets is of viial importance to tbose who are farming large tracts of land, but not so much so to those who are in a small way, and who usually dispose of surplus produce at their own dour, or trade it at the nearest store. Canadian farmers can
always get a fair price for their produce, without much trouble. This is very different to many of the western states, where some time ago grain could not be sold at any price, but was either allowed to rut or burnt. This is not fancy but a fact.
The Canadian winter is cold, but there is plenty of fuel at your very door, game is not plentiful, but'the rivers swarm with fish. There is a peaceful population, crime in some districts being unknown, thero are properly constituted courts vi law where the judge chews not, neither duo- he ¿moke in court. A man working there fur himself, as he is obliged to do here for a master, will find a very different result; he will be paid in produce as he goes on, and the more ho toile the better will he be, for every aere ha clears and cultivates not only re
fireeeuts present gain, but future independence; his and will be gaining value yearly. It is truly a working man's country, and in it he thrive* and Uves in health and comfort." To those who are blest with bodily health and strongth, and especially those who have grown-up families, and have a little money saved, I would say go to Canada.
If any of your numerous correspondents are thinking of Canada, I will gladly send moro particulars as to cost, capital required, or any other information of which I am poisttsded» M.ISKELONUUK.
 Sir,—If I understand the "Harmonious CottonSpinner" rightly, ho has nuw discovered a slight draught between the Up ruller and feed rollers, in the make of engine in which he challenged me to find a draught; and on becoming aware of the fact that the fluted rollers take up more length than plain ones of the same diameter, be, it appears, instructed their carder to "counteract the difference by nailing slabs of wood ¿in. thick round the lap roller." making it 6Jin. diameter instead of Gin. as before. He will perhaps bo surprised when I tell him that there is still a draught between the rollers, for, supposing the feed rollers were plain rollers 11 in. diameter, in order to get the real working diameter we must add to them the thickness uf the lap between the two feed rollers; if we take this thickness at ¿th of an inch, which I think ho will allow is reasonable enough, 48 x Ц
wc should hove a draught of = 1*07.
14 x Ü
I am well aware that machines are frequently altered after leaving the maker's hands—sometimes for better, sometimes for wor*e. I have seen fluted rollers turned down into plain ones, and lapped with card fillet, but the wheels have been changed in order to keep the relative speeds as before.
He asks me how " I would account for a carding engine working with tho same arrangement ho quoted, with rollers covered with fillet instead of being fluted." In ascertaining whether there is or is not a draught between the rollers, I told him in my last letter that with fluted rollers, I should take out the taker-in, and measuring the lengths delivered by lap roller and feed rollers, notice the différence between the two. Where the rollers are covered with card filleting, I should nut take out the taker-in. 1 should merely break off the lap from the roll at 1£ yard from the feed rollers (of course with the feed rollers out of gear), put the wheels into gear, and after the lup roller had revolved twice, throw them out again, then measure the length of lap left, and see how tho difference between it and Ц yard corresponded with the length that two revolutions of the lap roller would give. This is the only practical way to settle the matter. He says "I am wrong in the statement about the length fluted rollers will take up." If bethinks so, why does he not make the trial as suggested, which can be done in ten minute-, and forward the result for the benefit of your readers? If he is nut willing to do this, perhaps some one else will test tho matter and decido between us. From what he now says, it appears that he has not boeu dealing with the '• practice," but the "theory of cotton spinning." Had he told us this ut first, we should have understood him much better. I certainly did not think that any one would have taken "Mutual Improvement's " question to be one of '* theory," neither would anyone suppose, on reading " H. C. S.'s " first and subsequent letters, that he was dealing wth thoory ouly. 1 and others had stated that there it a draught between lap and feed roller. He said there is not, and challenged me to the proof in any one of the 150 engines, particulars of which he gave. I call tins dealing with the question practically.
Theoretically I agreo with him that " there ought not to be a draught there," but practically it is found that a draught is necessary fur reasons given before, added to which I may mention that there is Hoiuotimes such а "plague" as the hip " licking," which a slight draught has a tendency to prevent. I grant him that in most of the books published on cotton spinning, the draught is taken between feed rollers and delivery rollers, but liko Mr. Slater, I am no believer in books on cotton spinning, especially in any I have seen bv recent writers on the subject: mostofthein are merely condensed reprints from works uf former writers, who wrote at a time when the engine was not fed with a lap, as at present. Formerly the cotton was spread by hand ou a feeding cloth, or lattices, much in the same way as is now done on the feeder of a lapping machine. At that time it might be quite proper to begin at the feed rollers in taking the draught of the engine. "H. C. S." will find that all our writers of works on cotton spinning do not begin at the feed rollers, as he supposes. I am not acquainted with many, but if he will look into " Scott's Practical Cotton Spinner,"^which 1 suppose fs considered a standard book, he will find that he begins at the lap roller, and gives the "draught between lap rollers and feed rollers Г08. But supposing there was no draught between the rollers, I think it be-it to begin at the lap roller on account of the difflculty there is in finding at what rate the feed rollers, whose surfaces are nut plain ones, deliver the lap to the taker-in.
I referred "H. С. Я." to tho maker of a yarn tester, as I did not wish to encroach on your space with a description. I thought then, as I think now, that if ho thought proper to write be would perhaps get better information than I could give, as there may have been improvements made since it came out, now some years ago, of whiah I know nothing.
I owe Mr. Slater an apology for having commented on his method of taking draughts, before I had given that attention to his second letter which I ought to havo
done had I been aware that in It he had resumed and continued the subject treated of In bis first letter. My remarks applied to his treatment of the question in his first letter. I can injure him I had not noticed the paragraph in his second letter to which he has drawn my attention in his last communication. Had I read his second letter more attentively there would have been no need for nfy comments, as I find wo agree almost exactly in our 'methods of taking draughts.
I hope Mr. Slater will uot be scared away by tho "ghost" he has risen, or that he will bo in tho least disheartened by the numerous attempts made by tho " lads" to pin him into a corner, there is no harm at all in them, it is only a way they have of seeking information, and they would be no worse at all for a little "peppering " if oar Editor would allow it. Some 18 months ago, under an altered nom de plume, I had the pleasure of a passage at arms with one of them. I found no jiariu in my assailant, although soino ugly thrust« had to be parried, and I have no doubt but that both of us were better after the encounter.
Factory lads are not at all thin-skinned, they care nothing about a little rough handling now and then. They are used to hard knocks : it In rather an amusement for them, and one way thoy have o,' enforcing their arguments. Under your excellent management they will mend their manners, as yon cannot afford to indulge them at the expense of your other contributors, «specially now that your space will become more valuable by tho accession of strength from the contributors to Scientific Opinion.
I should be very sorry if I thought that anything I have said has given offence to Mr. Slater. I have read his letters with great pleasure, especially the one on pago 330, wherein he gives some sound advice, and which I think goes a long way towards explaining the poser which he set us to think out for ourselves. There are also some very good reasons given why he advocates the arrangement of draughts he givei^ (in advocating a more equal distribution of draughts he docs not stand alone: similar views are held by a great many. Scott in his book, for a total draught of 6'12, gives the draughts for three Hues of roller* thus—" between back and middle 2-25," " between middle and front 2'72,"), and also why he condemns a "considerable" draught in draw boxes at the engine head. New beginners in tho study of the art oí cotton spinning will do well to think over the matter in that letter. I have no doubt his letters have proved highly instructive to a great many engaged in cotton mills, by whom they will he much up
Erecfated. Mr. Slater is very weñ able to take care of iniself, so I will concludo with the hopo that he will at once lay the " ghost," and pass on to something of more substance.
В. ЛТ. R. [We have no objection to " factory lads " chaffing each other or " peppering" each other. But unfortunately they cannot do so here without occupying space «hieb, some who are not much interested in the »port think might be more usefully appropriated.—Ed. E.M.]
[801 Sin,—"Onlooker "says that in my description of silk bolters I assert there is not more than one-third the silk in actual use, the rest being taken up with rails and ribs. What I wrote, and what any one at all conversant with silk bolters knows to be a fact, is, as I stated, that there is no more than one-third of the м1к in the present silk bolters that is effectivo in dressing, simply because, for instance, in the size of bolter ho mentions there are six rails. Now each of these rails, continually as thoy reel, revolves, carrios the meal up with them to nearly the top of the reel, from whence it drops to near the bottom, so that while the rails are carrying tho moal up the silk is doing nothing, and i-i for nearly half the revolution of the reel, as the only part of the bilk that does any drowsing is where the meal drops, which is about half way between the ribs to the next rib, bywhich it is carried up again; so thAt if I hail said that only half the circumference of the silk did its proper work in dressing, I should have been nearer tho mark. E. Pattes.
A SQUARE-BAR MICROMETER.
 Sin,—I am afraid tho letter of "Omicron," page 37У, if it does not actually mislead "F.R.A.S.," will not increase his information. If my recollection servos me rightly, Mr. Cooper does not call the apparatus he used in determining the co-ordinates of the stars in the "Markroo Catalogue" land described in the introduction to that work) а *' bar micrometer," but а" squarebar micrometer," which is likoly enough to be a very different instrument, as no doubt the name refers to tho arrangement of the bars, Mr. Cooper's bars themselves boing by no means square ones. The name w«s given to it, I should say, much in tho same wav as it was to the old rhomboidal micrometer of which La Caille made such good use, and of which instrument Mr. Cooper says his is a modification.
Why does not Mr. Holden write to Messrs. Cook & Sons, and ask them for the information he requires? He might then know exactly what the instrument is, and be aide to enlighten some of us through the medium of your very excellent journal.
Henry T. Vivian.
THE CAUSE OF STORMS.  Sir,—I should very much like, with your approval, to write а рарог on this subject I in accordance with Mr. E. Jonofl'e suggestion), when I have concluded my paper on " Comets and Meteors."
Richard A. Proctor.
REPLIES TO QUEBIES.
[9687.]—ELECTRIC LOCOMOTIVE.!—A look at one in an instrument maker's window will be better than я lengthy description, which, for a mere toy, would have little interest to others. There is, or was, one at Negretli & Zambra's, Holhorn, close to Hatton-garden, now on the new viaduct,—810Ma.
Г2647.] — COLOURED PRINTS. —" Blackburn" will get these at any large stationers'.—Вдох Rvmea.
[2652.1—SULPHATE OF ZINC is made by washing tho calcined and effloresced sulphide nf zinc, or blende, and evaporating till the liquid crystallizes.—H. U.
[2652.1 — SULPHATE OF ZINC—Is manufactured by dissolving zinc In sulphuric acid, and crystallizing. Vast quantities are thrown away in the form of battery solutions, and as a residue from the making of hydrocen gas, especially by plumbers who use the lead-soldering process.—Siosca.
[2658.]—CHEMICAL SOLUTION.—I have some of the same precipitate set by me for examination, when I have time at disposal for it. I suspect it is an oxychloride.—Sigma.
[Э665.1 — INDICATOR. — Apparentlv the querist means "shocking" coils, as shown in tin- streets and elsewhere, rather than what are more usually called induction coils (though they are really the same things differently made). It is a purely mechanical matter, and may be made by leading a cord from the handle, bv which the tube is drawn out \>> the arbor of the indicator. I have seen a similar index fitted to a magnetic electric instrument, to show the distance to which the armature is withdrawn. It only Indirectly indicates the force of the current by really showing the condition in which the instrument yielding is placed, but has itself no connection with the electrical action.—Sigma.
[266R.1 — SKETCHING FROM NATURE.—" Typograph" can get acetate and muriate of cobalt at Mr. Cox's, Ludgate-hill; Messrs. Mottershead, Manchester, and of most dry saltera. I don't know the price, but they will send catalogues of chemical!« for a stamp.— Satl Rystea.
[2669.] MAGNETISM.—The answer to this wonld be a treatise. And should accordingly be sought in works treating of the subject.—Sigma.
[2699.]—CROQUET RULES.—"W. F." can obtain these of Messrs. Routledge, Broadway, Ludgatc, E.C. I do not understand what he means by "marking" boxwood rings.—Satl Jtv.MK.v.
[8764.] — EBONITE.—The shape of articles made of this substance cannot be altered after once casting.— Sacl Rvmea.
[8805.] —REDNESS.—The flushingof the face of which "Rouge " complains is constitutional and may be relieved by a strict attention to diet. Has " Rouge " tried the effect of " making up his mind " not to let his face turn red ?—Sacl Rvmka.
[3811.]—GUAIACUM.—The wood and gum of this tree were at one time considered specifics in syphilitic diseases, and the gum is still used for a variety of purposes in medicine. As to which is the best way to obtain all the medicinal properties of herbs, Infusion or distillation, that would of course depend on the nature and properties of the particular herb.—H. U.
[3811.]—GUAIACUM PLANT.—The querist asks for some particulars about the gualacum "plant." Might this not be a mistake? There is a gnaiacum "tree," lignum vita?, л tree of the West Indies, 40ft. high, the wood of which, гсшАгкаЫе for its hardness and toughness, is much employed for pieces of machinery, and the scobs and raspings used in medicine as a sudorific; its resin is also used mcdicinaHy. Botanical паше, (luyarum Officinale, Zygophyllaceie; the tree can be seen at the Kew Gardens, in the tropical stove. The name of guyacum tree is sometimes given in British Guiana to the Ton quin bean tree, Ditpetrix ottorata. If the querist means " Guaco," I beg to say under that name have been introduced in the trade the stems and leaves of the Guaco plant of Columbia, and in its native country as an antidote for snake bites, and recommended In Europe against cholera; Botanical плюс: Mikania Guato, Humb. and Bonpl. The stems of Ârittolochia rymharvm are also imported sometimes under the name of "Guaco."—Bebnabdin.
[8828,]—KID BOOTS.—"Old Scrub" should try sour milk to keep the leather soft.—H. U.
[3851.]—HARNESS.—I thought "Equestrian" would have had a host of replies to his query 3851, or I would have answered it before this. Пе does not say whether it is liArnees or riding-saddle and bridle, but I will give directions for both. If k. is harness, let him wash it perfectly clean with warm water and soft-soap, and, when drv, apply neat's-foot oil and black dye, mixed (he can mix them by adding a -mull quantity of salts of wormwood), when they will be well Mucked and pliable. Then apply on the top of the straps either Herriss*s or Wrigley's Composition il prefer the latter), and he can keep his harness in good condition, and have it look well. At the same time, by applying the oil and dye to the bottom or under parts of the straps, and composition to the top, they will always be pliable, and have a good polish on the top. If it is a riding-saddle, let him wash in cold water and soft-soap until free from dirt; then apply soft-soap with a woollen cloth (about two tablespoonfuls would be enough for a saddle), which will dry in. If he wants hi« saddle to have a yellow appearance, he must infuse a pennyworth of hay saffron in about four or five tablespoon!uls of water, and apply before the soft-soap; when he has applied the soft-soap, let him rub on to a piece of woollen cloth a piece of bee's-wax till he gets a thin coat on the cloth, and then finish his saddle off with it, rnbbiug till he gets a good polish. He don't need to fear for his '• inexpressibles ;" if he does, let him trv it before mounting with his white pockethandkerchief: if anything comes off, it is the íanlt of not washing clean at the beginning, and not the bee'swax. If he ruts it on as "New Subscriber" recommend в, he might bo afraid, or if he put oil on. as " Banting " advises; but I think "Banting " is "chaffing" a bit. He says, "If lie can," apply a little neat'sfoot oil "where there is no wear" it will be all the better. I have made and repaired a good many, but never yet found out where the parts lay that had :io wear upon
them. I am afraid " Banting " don't know much about the dressing of hog skins, or ho would not advise oil for a riding-saddle. Sadoluu.
[3865.]—LABEL MATRIX MAKING.—The gun-metal matrix Is stamped by dealing it a heavy blow with the steel die.—H. U.
[3877, 4431.] — RETINNING CAST-IRON WARE.— By first thoroughly cleaning from all grease, &c, with caustic soda, then, if at all rusty, with diluted sulphuric acid, then making hot, and rubbing with sal ammoniac, and raising the heat sufficiently to melt the tin, which is to be evenly spread over with a wad of cloth or tow. The tin should he free from lead, though, I believe, a small portion of lead is commonly used, as it makes the tin melt easier and run more freely.—Sigma.
[8887.]— SEWAGE.—"Sewer" should get "The Sewage Question," by F. C. Krepp. London : Lougiuau'B.— Saul Ryhea.
[8898.]—AIR GUN.—If W. Jones must have a walkingstick air-gun, he must buy one. He will find it a deal cheaper than making it.—J. K. P.
[8901.] —SLATE CISTERN.—" Salmo Salar" had better get his cistern cased with thick wood, or some day it will split altogether,—Sat-l Ryhea.
[3908.]—BRASS CIRCLE.—"Scorpio " will find it an endless job to perform with the compasses. He had better take it to some one who divides for the trade. See my letter (608) p. 193, Vol. X.^J. K. P.
[8939.]—ELECTROTYPING.—"Herbert" will not be able to take electrotypes in brass, as that metal is a compound; but he may take them in iron. Messrs. Hamid, of Fetter-lane, have a patent for a process I which they call " aciertype," and certainly the " electros" are very clean and hard, and will stand the chemical action of coloured inks. Perhaps "Sigma" could tell him how to deposit Iron as an electrotype. Silver, of course, is done in tho ordinary way; but I suppose that is too expensive for '* Herbert.'"—Saus, Rymea.
[3960.]—THE BLOOD.—J. G. Jackson will find flowers of sulphur, taken in eithertreaclc or milk, a good purifier of the blood. Decoction of scrsnparilla i« possibly better, i hut considerably more expensive. Dandelion tea and nettle ten are likewise supposed to be useful. But the best way to purify the blood is to prevent it becoming impure, by attention to diet, cleanliness, and a proper, control of the passions.—Sakkos.
Г8971.]—DISPLACEMENT OF SHIPS.—«■ О. B. IV
will find the following method for computing the dis-; pincement Of ship* to be sufficiently near for practical purposes. 1st, separate the part of the model of the ship that is to ho Immersed from the part that is to be above water, then weigh the former and make up a rectangular block equal in weight from the same sort of material as the model is made with, which of course is the same in bulk as the immersed part of model. Now, find the cubical contents of the block by multiplying length,' breath, and depth continually together, and dividing the I product by 85 you will have the displacement in tons in j ordinary sea water.—W. Felton.
[4034.]—BOAT STEERING. —"Excelsior" should steer his whale boat with an oar. On the west coast of South America these boats arc much used, and nre always steered in that manner. I have tried to adapt a rudder to them, but it has been always a failure. They arc often fitted with a'centre board, which makes them hold a better wind.—West Coaster.
[4078.]— TESTS FOR TOBACCO AND NUX VOMICA.—" Barbados " seems to have rather an indefinite idea about Ihe manner of testing for vegetable alkalrids when ho asks for the tests of Nux Vomica. The alkaloids belonging to the strychno tribe are as follows :—Firstly, Strychnia and Brucia: eecondly, the less important Cacotheline, Igasuria, Antidisentérica, Sabadilla. and Colchinea. Inasmuch as all these prementiomed bodies are contained in Nux Vomica, it wonld be rather a complicated experiment to ascertain the existence of those substances which together constitute the i>ropcrties of Nux Vomica. I should therefore strongly advise " Barbados" merely to test for the most important acting principle, viz., Strychnia or Strychnine, a few of the tests of which we subjoin :—When pure it is turned yellow by concentrated nitric acid, and yields a nitrate of anew substitution base, nitro-strychnia. It Brucia be present, ав is usualin most commcrcinlspccimcnsof strychnine, the colour produced by nitric acid will be deep orange or red.—8. A minute quantity of strychnia, with concentrated sulphuric acid, and a fragment of peroxide of lead, or what is still better, of potassic dUhroiuate gives a beautiful violet tint, which gradually lades into a pale rose colour; other oxidizing agents produce a similar effect.—8. With solution of auric chloride, salts of strychnia give a bright blue colour.—4. Forfeiting minute quantities of strychnia in compound organic liquids, a simple method was practised by Curveillc, which consisted In rendering the liquid alkaline with potassa, and adding ü per cent, of chloroform, and well stirring ; the chloroform takes u\i the strychnia, and appears in the crystalline form on evaporation. Brudu or brucinc
may be detected in Nux Vomica by the following :—
1. Mix with tartaric acid and add hydro-sodie carbonate and the negative result will distinguish it from strychnia.
2. If a little staunona chloride be added a beautÜul violet colour is produced.—If concentrated nitric acid be be poured on brucia it emits a colourless gaa, which has. a smell resembling that of apples. Should " Barbados" require the tests for the less important alkaloids, which I have not thought needful to enumerate, I -h til at any time be happy to furnish them. Tobacco, like Nnx Vomica, contains among other less known alkaloid» nicotine or nicolytia, And hyoecy amine. Nicotino may be distinguished by the following tests:—1. By the addition of perchloride of mercury which forms a white precipitate.—'2. A like result is produced by acetate of lead.—3. And also by both the stannic aud stannous chlorides.—4. Cupric salts with an excesa of nicolytia give я blue colour similar to that produced by an excess of ammonia.—5. When gaseous chlorine passed thron gha solution of nicotine a blood red liquid is produced.— Walter J. Nicholls.
[4096.]—MACHINE FOR MAKING SODA WATER» GINGER BEER, Ac—In answer to " I). W. L." I stud the above drawing and description for making *oÑrtawater, ginger-beer, or any other aerated waters. It consists of two barrels; the first is smaller than the second. and is for producing the carbonic acid gas h-ош слшпоп unslaked bine and diluted sulphuric л cid, «hi. J: are admitted by the bung X and the pipe with funnel A; the gas is conveyed by the pipe В into the second barrel w hich contains the WAter to be aerated, which rising through tho water to the top of the barrel lurtes tho water up the pipe D which is connected wtth the bottling apparatus F, (a section of which is seen in F«*, ï), G the lever, E the support, H the bAtle, -J a bed for the bottle, К the stand. In Fig. 2, 1) и the supply pipe from the barrel, and is connected with another pipe or cylinder at right angles, which is w idened. at the bottom for the reception of tho bottle neck intended to be tilled. The pipe or cylinder contains a cork C, above which is a nicely fitting piston P: fthw in tho widened part is a ring of india-rubber, against which is pressed the neck of the bottle to prevent the liquid from (-pilling. The bottling or corking apparatus fa worked in the following manner. A* soon as the bottle is tilled bv the supply i'ipe I>, the cork is quickly forced down by the lever L, and the pbton P into tho bottle B, which is fastened down directly; all tho bottk s arc wired ready for filling.—Jok.
[4101.]—DIFFERENCE OF TEMPERATURE BENEATH TREES.—If "K.'s" senses did not deceive him the fact is curious, and well worth further and moro accurate observation. The only cause which seems to be assignable is that the foliage ot some trees evaporate faster, and so cools the surrounding nir more perceptibly than others. If "K." has time and opportunity tötest this he inav readily do so by a wet and dry bulb thermometer piaced beneath the trees which appear to have» this remarkable effect. If the thermometers so placed stand at different heights the effect is due to evaporation; if they do not vary it must be attributed to some other cause, probably draught, causing coolness by evaporating the moisture on the skin, and arising from local causes or from density of foliage rather than from any chemical or analogous effect produced on the air by the trees themselves.—-J. B.
[4110.]—MAGNETISM.!—In the case put by Mr. Preston, no doubt there would be a greater attraction displaved bv tho cut ring at the point* of severance. This is easily explained by the ordinary theories of magnetism, and even more perfectly by that which I set forth in my electrical papers. The force depeniL* on tho molecnlcs, and is exerted by nil of these on «amending molecules in the ratios of their пеагпел and capacity for magnetism; As long as the iron ring is complete, the molecules composing it arc in the closest possible union. Therefore their actions are almost completely confined to the ring itself, just as with a magnet at some distance within its extremities; but when it is cut the opposed faces are no longer any closer to each other than to the iron tilings put iu contact with them, and their influences will therefore 1*> partly diverted to the filings. The effect of charge with tho Ithumkorff coil would greatly depend on the stato of insulation of the battery and instrument from tho earth, but it is well known that static charge can bo produced by putting one pole to earth; in fact it is so with even a single battery cell or any elect nun otion, tho degree or tension of such charge depending on tho electromotive force of the arrangement.—Sioma.
[4118.] — PROBLEM. — THE FOLLY OF ALGEBRA.—Without entering into the merit or M foil*" of Algebra. "Gimel" has not correctly stated tho answer to the " problem." If a genth man applies £187 annually to the pavment of interest and principal of a mortgage debt of ¿2000 at öper cent, interest, it is not tine, as ''Gimel" assumes, that "there would remain £87 per annum" for the payment of the debt. ТЫч would be so te thrfirtt угат only. Thus, the pavment of £187 in the first year would comist of interest £10O. principe] £b7; iutbc iecti.d jcar, interest (on £'¿IC0