articles in the pages of the ENGLISH MECHANIC. I must confess that I am not a talented chemist; and it may be also true that "C. D. C." is right in his remark that I know nothing about the carburization of gas. Be this as it may, I will now add some of the facts I do know respecting improving common coal gas by the means of carburization. For nearly two years the process of carburization was tried in the city of London public lamps, under, I believe, the direction and inspection of Dr. Letheby, and yet was abandoned, and has not again been adopted. Great economy, with increase of light, was at that time promised, according to the theory and estimate of the projectors.

To ensure economy in the consumption of gas, the ordinary burgers, consuming five feet per hour, were changed to those which would only consume three feet per hour. Of course the gas company's bill was materially diminished. But 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 five-feet-per-hour burners.

I am well acquainted with the fact that within the last three or four years the principle of carburization 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, the 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 an 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. 3lb. of the above were placed into a suitable vessel in such a manner as to expose a large surface for evaporation, and on passing atmospheric air there-through by means of a motive-power meter, a very large and rich flame, giving off abundance of smoke, was the result. This at the commencement, when adjusted to 5ft. per hour, gave a light equal to sixteen candles, but speedily the flame became perceptibly less; in a short time 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 flame whatever existed, as all the volatile constituents at the temperature had evaporated. On re-weighing the residue, barely one-half of the total quantity had been available. 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 small 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. 269, page 260, were not made without well considering the subject, and as I am in no way interested in any gas company, or the manufacture of gas, my object is not to make large gas

bills.

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 carburetting apparatus, but failed to realize anything like 50 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 carburetting process, the expense of apparatus and naphtha, the attention required, and last of all, and not the least objec tion, the dangers to be guarded against in the use of highly inflammable petroleum. Every gas consumer is not a practical chemist.

PRACTICAL TELEGRAPHY.

L. M.

[67] SIR,-Knowing your readiness to assist inventors to make known their inventions to the British public, I venture to send you a few lines concerning a telegraphic invention which is quite highly spoken of this side; it is an improvement in relay magnets, invented by William Smith, of Cincinnati. It is not easy to describe without drawings, and they are not to hand, but perhaps your readers will understand when I say that 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 upon as usual. The arrangement is claimed to be a considerable improvement, and the inventor will be glad to give particulars. Washington, June 21.

H. J. C.

A USEFUL TOOL FOR TREATING INCLINED OR LEVEL SURFACES.

have submitted to Prof. Pritchard what I take excep- | cular brass plate, B, with indices marked on it, through tion to in his review, pointing out where and how he the centre of which passes a small screw pin, upon has misconceived my meaning. If he admits that my which the needle, C, freely revolves. objections are valid, my obvious duty is to admit that W. GYNGELL. 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.

RICHARD A. PROCTOR.

THE SYMBOL .

are correct.

NATURAL SCIENCE IN MILITARY
EDUCATION.

[72] SIR,-In connection with the subject of Natural Science in Military Education 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 Education, wrote thus-"In fact it must march with the times and advance at the same rate as

ments in "Todhunter's Trigonometry" [69] SIR,-In answer to "Gimel," both the state- general education and intelligence advance." About that time so much greater attention was given to miliThe symbol is often used to represent the ratio, cally educated officers was so much more fully and tary education (or, rather, the high value of scientifi(3.14159-) between the circumference and the diameter of a circle; and the circular measure of two honestly recognized by the authorities) that staff apright angles is equal to 3:14159... Since the tech-pointments were no longer given hap-hazard, accordnical expression "circular measure" ing to caprice, favour, and family-ties, but officers is applied to that mode of measuring angles in which the unit is specially educated were only chosen, and the Staff the angle whose are equals the radius, it follows College itself was built, with a laboratory, &c., and the necessarily that the circular measure of two right Awakened interest in the cadet department of the students placed on a better footing than before. angles will be represented by the ratio of the arc of a Royal Military College, Sandhurst, had also about that semicircle to the radius, and this is, of course, equal time led the authorities to modify the plans and subto the ratio of the circumference to the diameter-jects of studies there in accordance with modern reratio invariably expressed, as Todhunter remarks, by the symbol T.

RICHARD A. PROCTOR.

MR. LOCKYER AND MR. PROCTOR. [70] SIR,-In a note to Nature, signed " "Editor," Mr. Lockyer asserts 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 part of Mr. Lockyer's note is that in which he remarks that, "surely Mr. Proctor is old enough (sic) 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.

for mathematical reasoning. I once "evolved from Mr. Lockyer has not always exhibited such contempt the depths of my moral consciousness," the 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. Considering 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.

I wish now to point out that I may have been over hasty in attributing wilful unfairness to Prof. Pritchard. He may have misconceived (not misinterpreted) the sense and spirit of my work. In this case, an apology will be due to him, which I shall be most ready to make. The case is now reduced to a very simple issue. I

OR LEVEL SURFACES.

[71] SIR,-I submit to your readers a useful little tool for treating inclined or level surfaces. It will be found 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

quirements. Classics had 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 have 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 either college have, of course, been mathematics, military arts and science (the latter 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 blundered on, pluck, persistency, and common sense carrying them through battles, campaigns, and administrations, with such losses, mishaps, and entanglements as were considered inevitable, and 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 chiefly found in healthy employment of body and mind, and in the satisfaction of intelligent views of natural phenomena. That military men appreciate and relish this source of useful pleasure 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 Hutton have urged their brother officers to cultivate geology and 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, &e., surely the man who has to fight nature at all points, in all parts of the globe, on all occasions, and that not for himself

alone, but in the interests-the vital interests probably --of his 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 mere y seeing the features of ground, but recognizing their meaning, 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 pass, spring, marsh, lake, river, and ford, so as to be able to master difficulties, avoid mishaps, and benefit by circumstances. He requires, too, a ready hand for other implements besides the sword. He must hammer the rocks, and study their characters at hand with the magnifier, as well as discern their nature from afar with his field glass. How else can he know what stone to choose for road metal, for instance? and with out 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 tanght at the Royal Military College, but the recently published Report of 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 teaching classies and mathematics, give such youths should come, do not teach physical science, but, 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 the desiderated plnek, dash, and wealth of public schoolboys may be, surely the more liberally educated students from other sources will beat them out of the field of competition, whatever limitation may be set to the subjects 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.

Thus the Royal Commission proposes a retrograde movement in national education, puts aside the 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 an 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, &c., 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 line and staff of the 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 the scientific culture 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 dise 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 the college list. Surely the cry of "too much work" is not true; the intellectual effort of military studies is not intense. 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 such matters. MEM.

para

THE FLUTE AND FLUTE-PLAYING. [73] SIR,-I have felt much interest in the letters which have appeared in your most valuable journal from Messrs. Leftwich, 66 Sable," and "Orion" проп 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 London 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" says "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 flute players must be limited, and I would recommend him to examine the fantasias of Nicholson, Frisch, Kuhlan, and others: he 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 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. Pratten, and at that time he played on the eight-keyed flute,as made by Messrs. Rudall & Rose, and in my opinion he never played better than he did then, for it seemed to me as if diffi culties 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 Prowse's flute ? I could name a host of others of the past, but I will come to the present.

Did "Orion" ever hear of Mr. Alfred Wells, who has been the solo flute in that magnificent band 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 one will accuse him of "botching or struggling" over the passages, be they ever so dimenlt, 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 tume, 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 construction (if such a thing exists) can be, and very indifferent performer even an instrument perfect in its 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 tnne, and a good tone, and quite lond enough for any flute (for I think, with one of our great conductors, that one does not want to play the trombone on the flute), and the fingering of the old flute, with a few exceptions, can be need, whilst there are also other fingerings which simplify the execution of certain passages. The Siccama flute is now made and sold by Messrs. Chappell & Co., and by Mr. Hanson.

I have no doubt that on the Carte Boehm finte many passages are much more 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 by Messrs. Rndall, 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 the late Mr. Clinton, I never conld see any advantage in it over the Siccama flute, and it is more complicated in its mechanism.

remain, As I dislike writing under an assumed name, I beg to HENRY CHAPMAN, Professor of the Flute.

[74]

THE SUN'S PARALLAX.

SIR,-" Veritas" asks me, on page 303, whether an angle at the centre of a circle is a measure of an arc of that circle. If the radius be known it cer tainly is so. His second question is, "Is the tangent an are 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

that of Venus, and S that of the sun. point on the earth's surface, such that PEV Let P be a and let all the lines be in the same plane. Then E V distance of Venus E P cot. P V E, and ES =

small a quantity as one second, much less to a frac tion of one; but I am confident that the parallax thus found will be that which is generally accepted to bu true. HUGO.

AN ENGLISH MECHANIC COLONY-HONEY-BEE

EMIGRATION.

[75] SIR,-I am glad to find that the thought expressed by your correspondent "Alexandra," page 340, exists in more minds than one. I have long expressed the belief that our present system (?) of emigration is not only careless and thriftless, but most reprehensible. leaving us, each one to shift for himself an army (in The harum-scarum way in which our population is now 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? are questions advisers are as numerous as their interests are diverse which meet the eye in every popular publication, and and multiplied. Since we profess to be so fond of what is natural, let us take an example from the crowded hand, the note of preparation is heard long in advance, hive. The honey-bee emigration is organized beforeand they go, carrying with them the habits and disci pline 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 exhausted in hopeless conflict with difficulties easy of design. At present the energies of our emigrants are often wasted by being scattered, and individual toil is removal by conjoined assistance.

Our emigration parties should be arranged long before starting, and shonld as far as possible represent a slice of the mother country, or at least of all the useful block of land with sea or river frontage, say, five, ten, and economic departments of it. For example, some or fifty miles square, is 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 would 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 the 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 the colony would be

another basis for selection. It would not do to have a

preponderance of one or two classes: 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, &c., &c., 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 be. 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 wel fare 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 ne cessities encourage or demand!

To illustrate once more. Let ns suppose that a dozen earnest men-intending emigrants-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 require ments 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 about 500, for the "better half" would be forthcoming at once, aye, and with

money too.

For the sake of the 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. The question is wider and deeper than at first appears. If, from the daily increasing disparity in numbers 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 civi lized 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 be their happiness to obey the Divine injunetion, Increase and multiply, and replenish the earth and subdue it."

M. D.

About three years ago, owing to the difficulty I experienced in getting thick rolled zinc, I tried iron as a substitute, and obtained results so unexpectedly good, that I have continued to use it ever since. My first trials were with cast iron plates, the battery arrangement being the same as Groves's-viz., platinum with nitric acid, and the cast iron in solution of salt; this gives very good action for a few hours, but at last the cast iron becomes covered with a plumbagine deposit which stops the current until it is entirely removed. Latterly I have used wrought iron either in plain water, weakly acidulated water, or solution of salt. Of the three I think the latter gives the strongest current; but there are some peculiarities about the behaviour of iron in this solution, which require to be studied. Frequently, but not always, the iron plates, after being taken out of the saline solution and allowed to dry, will refuse to act, and continue inactive 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 an arrange ment of saline and acid solution in each alternate cell, changing the plates from the one cell to the other after each removal.

It appears to me that the nitrons neid fumes are in this battery absorbed to a great extent by the iron solution in the outer cell, as I do not find them affect the

atmosphere of the room much. Will Sigma say whether this is likely to be the case. I am under the impression that nitrous acid gas has a strong affinity for iron solutions. If I am right it could probably be got rid of altogether by closing up the porous cell and leading it by a bent pipe into the outer solution. The first effect of the battery action appears to be to give a blue colour to the nitric acid. What is the cause of this? Is it owing to the formation of ferro-cyanuret? I had overlooked the description of Slater's battery nntil "Sigma's "last paper called my attention to it. His description, however, differs considerably from that given by "D. F. K.," page 132, in which the chief novelty appears to be the use of nitrates in the outer cell with the iron, nitric acid being used as usual with the carbon in the porous cell; and it is claimed that by adding nitrates and nitric acid to each respectively in proportion to the work done, the constancy of the 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 porous cell. Even fresh nitric acid has but little effect unless the old liquor is completely emptied out of it. I attribute this to the endosmosic action which converts both the inner and outer 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 use of nitrates in the outer cell is a step in the 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's" great courtesy in replying to enquiries, not always very reasonable, cannot be too often acknowledged by the readers of the ENGLISH MECHANIC. THOMAS C. HAINES. July 4.

EMIGRATION.-CANADA.

[77] SIR,-I can scarcely imagine a more perplexing position to be placed in than that of "Cotton Clerk," and having been in a somewhat similar one, can fully sympathize with him. Where is he to go? 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 supporters, 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 of them say, it is a very land 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 the settlements, murdering and scalping the poor emigrants, there is the continual pistoling, gouging, lynching, and cheating of the civilized white Indians to contend with. Not a word is said for Canada. One regards it as afflicted with a severe winter, but does not tell us that most of the western states are so afflicted; and that on the unsheltered prairies of the west is almost unbearable. Hot suminers 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 Englaud. I was glad to see the letter of "F.R.G.S." in support of the 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 are 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 of 200 acres may easily be procured in available situations, the terins being in either case nearly the same-an obligation to clear a certain portion of your allotment in a given time. That part of the bargain completed, the settler becomes undisputed owner of the soil. This is not, as some think. a life-long work, but can by industry be accomplished in a short time, and sufficient in a few years may be 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 vital inportance to those 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 door, 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 rot 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, there are properly constituted courts of law where the judge chews not, neither does he smoke in court. A man working there for 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 he toils the better will he be, for every acre he clears and cultivates not only reland will be gaining value yearly. It is truly a working presents present gain, but future independence; his man's country, and in it he thrives and lives in health and comfort. To those who are blest with bodily health and strength, and especially those who have grown-up families, and have a little money saved, I would say go to Canada.

of Canada, I will gladly send more particulars as to cost, If any of your numerous correspondents are thinking capital required, or any other information of which I am

possessed.

COTTON SPINNING.

MASKELONGUE.

My

done had I been aware that in it he had resumed and continued the subject treated of in his first letter. remarks applied to his treatment of the question in his first letter. I can assure 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 my comments, as I find we agree almost exactly in our methods of taking draughts.

I hope Mr. Slater will not be scared away by the "ghost" he has risen, or that he will be in the least disheartened by the numerous attempts made by the lads" to pin him into a corner, there is no harin 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 our Editor would allow it. Some 18 months ago, under at arms with one of them. I found no harm in my assailan altered nom de plume, I had the pleasure of a passage ant, although some ugly thrusts 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 noare used to hard knocks: it is rather an amusement for thing about a little rough handling now and then. They them, and one way they have of enforcing their argu ments. Under your excellent management they will mend their manners, as you cannot afford to indulge them at the expense of your other contributors, especially now that your space will become more valuable by the accession of strength from the contributors to Scientific Opinion.

[78] SIR,-If I understand the "Harmonious CottonSpinner" rightly, he has now discovered a slight draught between the lap roller and feed rollers, in the make of have said has given offence to Mr. Slater. I have read I should be very sorry if I thought that anything I engine in which he challenged me to find a draught; and on becoming aware of the fact that the fluted rollers 330, wherein he gives some sound advice, and which I his letters with great pleasure, especially the one on page take up more length than plain ones of the same think goes a long way towards explaining the poser diameter, he, it appears, instructed their carder to "counteract the difference by nailing slabs of wood in. also some very good reasons given why he advocates the which he set us to think out for ourselves. There are thick round the lap roller," making it 6fin. diameter instead of 6in. as before. He will perhaps be surprised arrangement of draughts he gives (in advocating a more when I tell him that there is still a draught between the equal distribution of draughts he does not stand alone: rollers, for, supposing the feed rollers were plain rollers siinilar views are held by a great many. Scott in his 1in. diameter, in order to get the real working diameter book, for a total draught of 6-12, gives the draughts for we must add to them the thickness of the lap between three lines of rollers thus-"between back and middle 2-25," "between middle and front 2-72,"), and the two feed rollers; if we take this thickness at 4th of an inch, which I think he will allow is reasonable enough, draw boxes at the engine head. New beginners in the also why he condemns & "considerable" draught in

we should have a draught of

48 × 13 14 x 6

= 1.07.

I am well aware that machines are frequently altered after leaving the maker's hands-sometimes for better, sometimes for worse. down into plain ones, and lapped with card fillet, but the I have seen fluted rollers turned wheels have been changed in order to keep the relative speeds as before.

study of the art of 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 be much appreciated. Mr. Slater is very well able to take care of at once lay the "ghost," and pass on to something of himself, so I will conclude with the hope that he will

more substance.

B. W. 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 which some who are not much interested in the sport think might be more usefully appropriated.-ED. E.M.]

1869 AND 1870.

[79] SIR,--I beg to send you the temperature 2ft. below surface last year and this for June:

June 1-3 4

1870.

1869.

He asks me how "I would account for a carding engine working with the same arrangement he 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 covered with card filleting, I should not take out the difference between the two. Where the rollers are COMPARATIVE TEMPERATURE DURING JUNE, taker-in. I 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 lap roller had revolved twice, throw them out again, then measure the length of lap left, and see how the difference between it and 1 yard corresponded with the length that two revolutions of the lap roller would give. This is the only practical way to settle the matter. says "I am wrong in the statement about the length fluted rollers will take up." If he thinks so, why does he not make the trial as suggested, which can be done in ten minutes, and forward the result for the benefit of your readers? If he is not willing to do this, perhaps some one else will test the matter and decide between us. From what he now says, it appears that he has not been dealing with the "practice," but the "theory of cotton spinning." Had he told us this at 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 theory only. I and others had stated that there is 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 this dealing with the question practically.

SILK BOLTERS.

[80] SIR,-"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 silk in the present silk bolters that is effective in dressing, simply because, for instance, in the size of bolter he mentions there are six rails. Now each of these rails, continually as they reel, revolves, carries 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 the meal up the silk is doing nothing, and is for nearly half the revolution of the reel, as the only part of the silk that does any dressing is where the meal drops, which is about half way between the ribs to the next rib, by which it is carried up again; so that if I had said that only half the circumference of the silk did its proper work in dressing, I should have been nearer the mark. E. DAVIES.

A SQUARE-BAR MICROMETER. [81] SIR,-I am afraid the letter of "Omicron," page 379, if it does not actually mislead "F.R.A.S.," will not increase his information. If my recollection serves me rightly, Mr. Cooper does not call the apparatus he used in determining the co-ordinates of the stars in the "Markree Catalogue" (and described in the introduction to that work) a "bar micrometer," but a " squarebar micrometer," which is likely enough to be a very different instrument, as no doubt the name refers to the arrangement of the bars, Mr. Cooper's bars themselves being by no means square ones. to it, I should say, much in the same way 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.

REPLIES TO QUERIES.

[2637.)-ELECTRIC LOCOMOTIVE.]-A look at one in an instrument maker's window will be better than a lengthy description, which, for a mere toy, would have little interest to others. There is, or was, one at Negretti & Zambra's, Holborn, close to Hatton-garden, now on the new viaduct.-SIGMA.

[2647.]-COLOURED PRINTS." Blackburn" will get these at any large stationers'.-SAUL RYMEA. [2652.)-SULPHATE OF ZINC is made by washing the calcined and effloresced sulphide of zinc, or blende, and evaporating till the liquid crystallizes.-H. U. [2652.] 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 hydrogen gas, especially by plumbers who use the lead-soldering process.-SIGMA.

[2653.]-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 oxy

chloride.-SIGMA.

means

[2665.] INDICATOR. Apparently the querist "shocking" coils, as shown in the 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, by which the tube is drawn out to 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.

SADDLER.

[3865.]-LABEL MATRIX MAKING.-The gun-metal matrix is stamped by dealing it a heavy blow with the steel die.-H. U.

[8811.]-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.

[8811.]-GUAIACUM PLANT.-The querist asks for some particulars about the guaiacum "plant." Might this not be a mistake? There is a guaiacum "tree," lignum vitae, a tree of the West Indies, 40ft. high, the wood of which, remarkable 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 medicinally. Botanical name, Guyacum Officinale, Zygophyllaceae; 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 Tonquin bean tree, Dypetrix odorata. 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 name: Mikania Guaco, Humb. and Bonpl. The stems of Aristolochia cymbarum are also imported sometimes under the name of "Guaco."-BERNARDIN.

[3828.]-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. He does not say whether it is harness or riding-saddle and bridle, but I will give directions for both. If it is harness, let him wash it perfectly clean with warm water and soft-soap, and, when dry, apply neat's-foot oil and black dye, mixed (he can mix them by adding a small quantity of salts of wormwood), when they will be well blacked and pliable. Then apply on the top of the straps either Harriss's or Wrigley's Composition (I 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 his saddle to have a yellow appearance, he must infuse a pennyworth of hay saffron in about four or five tablespoonfuls 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, rubbing till he gets a good polish. He don't need to fear for his inexpressibles;" if he does, let him try it before mounting with his white pockethandkerchief: if anything comes off, it is the fault of not washing clean at the beginning, and not the bee'swax. If he puts it on as "New Subscriber" recommends, he might be afraid, or if he put oil on, as "Banting "advises; but I think "Banting" is "chaffing" a bit. He says, "If he 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 no wear upon

SAUL RYMEA.

[8898.]-AIR GUN.-If W. Jones must have a walking: stick air-gun, he must buy one. He will find it a deal cheaper than making it.-J. K. P.

[3901.]-SLATE CISTERN.-"Salmo Salar" had better get his cistern cased with thick wood, or some day it will split altogether.-SAUL RYMEA. endless job to perform with the compasses. He had [3903.]-BRASS CIRCLE.-"Scorpio " will find it an better take it to some one who divides for the trade. See my letter (608) p. 193, Vol. X.-J. K. P. [3939.]-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. Harrild, of Fetter-lane, have a patent for a process 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 the ordinary way; but I suppose that is too expensive for " Herbert."-SAUL RYMEA.

[3960.]-THE BLOOD.-J. G. Jackson will find flowers of the blood. Decoction of sersaparilla is possibly better, of sulphur, taken in either treacle or milk, a good purifier but considerably more expensive. Dandelion tea and nettle tea 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.-SARKOS.

[8971.]-DISPLACEMENT OF SHIPS.-"G. B. D.' will find the following method for computing the displacement of ships to be sufficiently near for practical purposes. 1st, separate the part of the model of the ship that is to be 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 product by 35 you will have the displacement in tons in 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 are much used, and are always steered in that manner. I have tried to adapt a rudder to them, but it has been always a failure. They are often fitted with a centre board, which makes them hold a better wind.-WEST COASTER.

[4078.]-TESTS FOR TOBACCO AND NUX VO. MICA." Barbados" seems to have rather an indefinite idea about the manner of testing for vegetable alkalcids when he asks for the tests of Nux Vomica. The alkaloids belonging to the strychno tribe are as follows:-Firstly, Strychnia and Brucia; secondly, the less important Cacotheline, Igasuria, Antidysenterica, Sabadilla, and Colchines. Inasmuch as all these prementioned bodies are contained in Nux Vomica, it would be rather a complicated experiment to ascertain the existence of those substanses which together constitute the properties 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 a new substitution base, nitro-strychnia. If Brucia be present, as is usual in most commercial specimens of strychnine, the colour produced by nitric acid will be deep orange or red.-2. A minute quantity of strychnia, with concentrated sulphuric acid, and a fragment of peroxide of lead, or what is still better, of potassic dichromate gives a beautiful violet tint, which gradually fades 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. For testing minute quantities of strychnia in compound organic liquids, a simple method was practised by Curveillé, which consisted in rendering the liquid alkaline with potassa, and adding 2 per cent. of chloroform, and well stirring; the chloroform takes up the strychnia, and appears in the crystalline form on evaporation. Brucia or brucipe

may be detected in Nux Vomica by the following:1. Mix with tartaric acid and add hydro-sodic carbonate and the negative result will distinguish it from strychnia. 2. If a little stannous chloride be added a beautiful violet colour is produced.-If concentrated nitric acid be be poured on brucia it emits a colourless gas, 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 shall at any time be happy to furnish them. Tobacco, like Nux Vomica, contains among other less known alkaloids nicotine or nicolytin, and hyoscyamine. Nicotine 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.-8. And also by both the stannic and stannous chlorides.-4. Cupric salts with an excess of nicolytia give a blue colour similar to that produced by an excess of ammonia.-5. When gascous chlorine passed throngh a solution of nicotine a blood red liquid is produced.WALTER J. NICHOLLS.

[4096.]-MACHINE FOR MAKING SODA WATER, GINGER BEER, &c.-In answer to " D. W. L." I send the above drawing and description for making sodawater, ginger-beer, or any other aerated waters. It consists of two barrels; the first is smaller than the second, unslaked lime and diluted sulphuric acid, which are adand is for producing the carbonic acid gas, from common mitted by the bung X and the pipe with funnel A; the gas is conveyed by the pipe B into the second barrel which contains the water to be aerated, which rising through the water to the top of the barrel forces the water up the pipe D which is connected with the bottling apparatus F, (a section of which is seen in Fig. 2), G the lever, E the support, H the bottle, J a bed for the bottle, K the stand. In Fig. 2, D is the supply pipe from the barrel, and is connected with another pipe or cylinder at right angles, which is widened at the bottom for the reception of the bottle neck intended to be filled. The pipe or cylinder contains a cork C, above which is a nicely fitting piston P; also in the widened part is a ring of india-rubber, against which is spilling. The bottling or corking apparatus is worked pressed the neck of the bottle to prevent the liquid from in the following manner. As soon as the bottle is filled by the supply pipe D, the cork is quickly forced down by the lever L, and the piston P into the bottle B, which is fastened down directly; all the bottles are wired ready for filling. JOE.

[4101.]-DIFFERENCE OF TEMPERATURE BENEATH TREES.-If "K.'s" senses did not deceive him the fact is curious, and well worth further and more accurate observation. The only cause which seems to be assignable is that the foliage of some trees evaporato faster, and so cools the surrounding air more perceptibly than others. If "K." has time and opportunity to test this he may readily do so by a wet and dry bulb thermometer placed beneath the trees which appear to have this remarkable effect. If the thermo meters 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 evaporat ing 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 displayed by the cut ring at the points 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 depends on the molecules, and is exerted by all of these on surrounding molecules in the ratios of their nearness and capacity for magnetism; as long as the iron ring is complete, the molecules composing it are 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 filings put in contact with them, and their influences will therefore be partly diverted to the filings. The effect of charge with the Rhumkorff coil would greatly depend on the state of insulation of the battery and instrument from the earth, but it is well known that static charge can be produced by putting one pole to earth; in fact it is so with even a single battery cell or any electromotion, the degree or tension of such charge depending on the electromotive force of the arrangement.-SIGMA. [4118.]

PROBLEM.

THE FOLLY OF ALGEBRA.-Without entering into the merit or "folly" of Algebra, "Gimel" has not correctly stated the answer to the "problem." If a gentleman applies £187 annually to the payment of interest and principal of A mortgage debt of £2000 at 5 per cent. interest, it is not true, as "Gimel" assumes, that "there would remain £87 per annum" for the payment of the debt. would be so in the first year only. Thus, the payment of £187 in the first year would consist of interest £100, principal £87; in the second year, interest (on £2000

This