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judge by is the movement observable among the stars, and, as the stars are themselves in motion, it is not easy to separate the effects of their own motions from those due to the sun's.

Still, this problem has been attacked and fairly vanquished by astronomy. Il is true we cannot here get certainty, because we no longer have absolutely certain relations to deal with. But,

as it is certain that, supposing the sun to be moving in a definite direction, there would result a balance of stellar motions in the contrary direction; we can obviously deduce the direction of the sun's motion, by noticing the direction towards which the stars show the most noteworthy balance of motion. This has been done, and in many ways. The result is that astronomers point confidently to the constellation Hercules and its neighbourhood, as including the point towards which the sun is speeding. His rate of motion has been estimated at about 150,000,000 miles per annum, or, between four and five miles per second.

I am only concerned here with the sun's proper motion, in so far as it relates to the earth's motions. The conception that the sun may be speeding through space with this enormous velocity seems, at first sight, so contrary to the fundamental hypotheses of modern astronomy, that many persons have been led to believe there is a real contradiction. They see that the earth's real path in space can no longer be looked upon as a closed curve, yet Kepler speaks of it as an ellipse; that, again, the earth, according to this new idea, is not travelling in a conic section, yet Newton says, all bodies under the influence of a central attracting force, such as gravity, must move in some conic section or other.

In reality, however, there is no difficulty. Modern astronomy only requires the earth and planets to move in ellipses with respect to the sun, not in space. Suppo-ing the sun at rest, and the planets moving in their present ellipses around him, and that then under the action of far distant suns, our sun began to travel through space, the planets would not (as Mr. Reddie fears), be left behind. They would be under the influence of those attractions as well as the sun. They would obey them then, precisely as he does, obeying all his influences as before. Thus their motions, with respect to him, would not be changed even by a hair's breadth.

CONCLUSION.

And here I draw these papers to an end. They have occupied much more space than I contem plated when I began, and yet each part of my subject has been dealt with far less completely than I could have desired. The fact is, a book, and no small one, is wanted to present at due length all the arguments which enforce upon astronomers the assurance that the Newtonian system is correct.

Would such a book be a desirable addition to modern astronomical literature?

I think not.

I believe that all sensible persons, even if, not capable of fully mastering the evidence in favour of modern astronomy, feel yet no doubts as to its truth. For them, then, such a book would be of little service. For the paradoxists-dividing them into two well-marked parties, the knaves and the fools-what can be done? One cannot make the blind see, let one talk ever so fluently about light; and those who, having sight, refuse to see, are blinder than the blind, according to the true old proverb. Towards the paradoxists, then, of either order, one should act as Sir John Herschel is said to have done, when a rampant one told him he had squared the circle. "Indeed," said the greatest living astronomer, raising his hat, "then, sir, I must wish you good morning."

But while a set treatise, in defence of modern astronomy, would be a waste of labour, I believe, and hope, the matter I have just completed may have been of use to many readers of this journal. The greater proportion of them, those in fact for whom the ENGLISH MECH ANIC is specially int nded, have not time for a thorough investigation of the subject, yet possess the power of appreciating to its fullest extent the arguments by which modern astronomy has been established. Knowing for whom I have written, I have not feared to be dry where my subject needed close and consecutive attention.

THE ROYAL POLYTECHNIC BARO-
METER.

HE name of Admiral Fitzroy will be Tmembered in connection, y, this ever of the most important improvements in the science of meteorology generally, and in the barometer particularly. The instrument which bears his name is perfect as a weather indicator, and as such

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has had a prize medal awarded to it, and is known as Admiral Fitzroy's prize medal barometer. But although perfect in itself as an indicator, and although clearly comprehended by those who are accustomed to the reading of such instruments, experience shows that to make it universally useful, its readings must be rendered in clear and definite language. Its price is within reach of all, and it only wants to be made intelligible to the most ordinary observer. To meet this requirement, Messrs. Davis & Co. have improved the apparatus in the manner shown in our engraving. Their Fitzroy barometer forms the base of the new instrument; this consists of the mercury tube with the cistern in one piece, which is enclosed in an oak case. On the lower part of the case is a thermometer, and opposite to this are diagrams of Admiral Fit:roy's storm warning siguals. These are surmounted by tables explaining their meaning. The novelty is in the upper portion of the barom ter, which will be seen to terminate in a circular dial about 10

inches in diameter. In the centre of this dial is the ordinary standard barometer scale, with its two verniers for taking the readings. These

niers are set to the rise or fall of the merce vermeans of a rack and pinion arrangement, worked by the two keys seen just below the dial. So far, we have the ordinary arrangement for taking the readings; but as this is not always clearly under stood, Messrs. Davis have supplemented it by placing on the right side of the dial two columns of remarks which refer to changes in the weather, one column showing the winter, and the other column, the summer changes. On the left hand of the dial these two columns are repeated, and are intended to record the weather of the previous day. The indications are effected by a simple and ingenious arrangement in connection with the verniers. On looking at the engraving, it will be seen that there are two hands or pointers radiating from the centre of the dial. These pointers are centred loosely on a pin fixed behind the tube, and each passes through a slot cut in the verniers, which thus hold them up. Now when the verniers are raised or depressed, the hands must follow the same direction; and according as the verniers are placed at the height of the mercury, so the pointers stop opposite to a statement of the weather that height indicates. The right-hand pointer is set to show the weather expected to-day, whilst the left-hand is set to record the state of the weather yesterday. The mechanism of the instrument is exceedingly simple, and is not liable to get out of order.

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PROCEEDINGS OF THE ROYAL ASTRONOMICAL SOCIETY.-MAR. 11, 1870. W. LASSELL, ESQ., F.R.S. IN THE CHAIR. (SPECIAL REPORT.)

the minutes the

had been read and coufirmed, the first paper communicated was from W. Marth, Esq., containing observations of position angles, and apparent distances of the Satellites of Uranus from the primary, which was ordered to be printed forthwith. Lieutenant Herschel communicated, through his brother, a paper remarking on a curious appearance, as seen on the Sun's disc. The author remarked that in October last, while preparing to observe the prominences of the Sun with a spectroscope, an unusual phenomenon presented itself, consisting, apparently, of a train of dark shadows and light streaks on the solar disc, which were at first thought to be sparks in the tube of the telescope, but the permanence of the phenomena did not permit of this explanation. The possibility of this extraordinary appearance being occasioned by the transit of a system of meteors, next occurred to the observer, and preparations were made to observe the circumstances of the transit with all the care possible. The image of the disc of the Sun was thrown on a screen, and the equatoreal telescope set in motion. The apparent size of the shadows was shown on the screen, and they were observed all that day. On looking at the Sun the next day, the same pheno. menon was observed; the objects were still seen passing in a continuous stream. The direction was 150° E. by N., or perhaps two streams not very far distant. The dark objects. were out of focus when the Sun was in focus, and were cloud, and notwithstanding the Sun's light they still seen when the Sun was partly obscured by were seen after they left the disc; and the smaller they were, the less was their velocity. The direction of motion of one only was retrograde; and one entered slowly, and then changed its direction. Every care was taken to notice every pec uliarity presented, till the observer convinced himself that he was watching the motion of a number of locusts, passing in continuous succession between the instrument and the Sun, and however curious the phenomenon might be in natural history, it author endeavoured to account for some of the was clearly not of an astronomical character. The peculiarities seen in America at the time of the Eclipse last year, by referring them to the same cause.

Mr. STONE remarked on the necessity of a change of focus, in attempting to explain any peculiarity of this nature, which was the best means of effectually settling the question.

Captain NOBLE remarked that in a previous number of the "Notices," would be found the re

marks of Mr. Reed, on a similar question, whose question. Mr. Stone hoped that the observers
suggestions led Mr. Dawes to focus for the well-would not confine their observations to any par-
known thistle seed."
ticular locality in the Corona, but examine all
positions of it.

Captain NOBLE communicated three short papers to the Society. One on occultations of Stars by the Moon; an observation of Venus, near her inferior conjunction; and an observation of the Zodiacal Light. In the second paper Capt. Noble said that the state of the sky prevented him seeing the planet till about two hours after her conjunction, when he saw a very narrow thread of light, not quite semi-circular, and saw the body of the planet projected on the sky beyond, sensibly darker than the surrounding sky. On the 3rd March, 7h. 40m., the author saw the most brilliant exhibition of the Zodiacal Light that he ever witnessed in this country. Besides its brilliancy, two peculiarities were noticed, namely. that it was very nearly perpendicular to the horizon, and the axis inclined to the ecliptic at an angle of 20o.

Mr. BROWNING exhibited some drawings of Jupiter, and remarked upon the many changes of forin and colour of the belts of Jupiter, the principal of which seems to have been a sensible widening of the Equatoreal belt to nearly double its former dimensions. Mr. Browning invited the attention of observers to a consideration of the Planet, which the peculiarities it presented renered interesting at this moment.

The PRESIDENT seemed to suspect some slight exaggeration of the colour and outline of the Equatoreal belt, but Mr. Browning defended his drawings, which appear to have been carefully made.

MODERN CHEMICAL NOTATION.

BY DR. FERD. HURTER.
(Concluded.)

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The sbove formulæ are sufficient to show us the use of the

chemical alphabet.

The first of these formulæ as well as the second and third

WHEN the atomicity or basicity of the element should be expressed by the symbol, then the letter is provided with another figure at the top, but this figure must be a Latin one. The sign O11 means accordingly that one atom of need no comment. Potassic sulphate is represented by a oxygen possessss two equivalents, or better, that one atom of symbol which is intended to convey an idea of the manner in oxygen can combine with two atoms of a monogenous elewhich the single atoms are connected. The sulphur being ment. This latter way of expression is the more general one. tetravalent is connected with two atoms of oxygen, which are When a number of atoms of the same element form one (if the compound must be saturated) again combined among group, then the Latin number at the top is the expression for themselves. Thus the group SO, has still two equivalents of the capacity of saturation of that group, or, as it is also sulphur left free to attract other atoms, which we find to be termed, for the atomicity of the group, or still otherwise, for oxygen atoms, each combined with an atom of potassium. the quantivalence of that group of atoms. In this way we The same formula would apply to hydro-potassic sulphate in write 0,11 or Mn,VI, and understand by it, that 5 atoms of one atom of potassium is replaced by one atom of sodium. The oxygen can combine with only 2 atoms of a monogenous group SO, we find in formula (7) representing alum to occur element, that 2 atoms of manganium can combine with 64 times. Alum is a sulphate like hydropotassic sulphate. atoms of a monogenous element. Each SO, is connected by 2 atoms of oxygen on the one side to the aluminium, on the other to either hydrogen or potassium. The metal aluminium has, like all metals of the same group, the property of occurring as a group of two atoms, which by their combination saturates 2 of the 8 equivalents of which they naturally consist. The two aluminium atoms are directly united with one atom of oxygen, saturating two more equivalents of aluminium, so that at last we have the group Al0 being tetravalent. This group replaces four atoms of hydrogen in four molecules of sulphuric acid, forming the compound ALOHO

The same rules apply to groups of atoms of different ele-
ments-for example, CO11 indicates that one atom of carbon
is combined with one atom of oxygen, and that this group is
able to combine with two atoms of a monogenous element.
When, however, a formula should be quite a rational one

and express the function of each equivalent of the various
elements forming the compound, then the letters and figures
are not always sufficient, and we have to enrich the chemical
alphabet with a few more signs. Instead of using a Roman
figure at the head of the letter to indicate how many atoms
of a monogenous element the element represented may com-
bine with, horizontal or radiating strokes are used, as many
in number as the Latin figure indicates. Thus one often finds

Or

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Trivalent.

Tetravalent.

The last paper was from Mr. Proctor, having reference to the Corona seen in total eclipses of the Sun. Mr. Proctor said that at the next eclipse of the Sun, which occurs next December, 0 instead of Ou, or in Spain, the attention of astronomers would be drawn to the Corona with a view of explaining the difficulties that it now presents. The author of the paper contended that the phenomenon witnessed could not be owing to terrestrial causes, for in cases of total eclipse the Moon is seen projected Some chemists use still more symbols. They represent all on the corona, which could not be if the light the monogenous atoms by a circle, and all the other elements was occasioned by the Earth's atmosphere. He by combination of as many circles as the element's quantivaadded that in an annular eclipse, the centre of lence requires. Such signs are represented by the following: the Moon has been seen darker than the edge; and that in partial eclipses the edge of the disc has been seen projected (dark) on the background of the sky, as often as the observer has looked for this particular, which would Monovalent. Divalent. seem to disprove the existence of an atmospheric glare. Mr. Proctor argued from Captain Noble's remark concerning the visibility of the dak part of Venus when in the neighbourhood of the Sun, the existence of a continual brilliancy which might be owing to the richer part of the Zodiacal Light, which increases in brilliancy as it approaches the Sun, and in the close neighbourhood of the Sun itself doubtless merges into the Corona. In concluding his remarks, the author conjectured that the Zodiacal Light itself was the collection of the richer portion of the meteoric streams, perhaps incandescent, where near to the Sun. He remarked that numerous meteor streams must exist, since the Earth meets with 56 of these systems, and that if the Great Comet of 1863 was followed by a train of meteors similar to that that accompanies Tempel's, the near approach of these to the Sun must produce an effect which can easily be supposed to resemble that witnessed where the Corona is brightest. Mr. Proctor hopes that the Society will form a committee to consider the best means of setting at rest the vexed question of the Corona, and made some suggestions which he thinks likely to produce that end.

It was asked at the meeting if the Government were proposing to render any assistance to astronomers that intended to go to Spain to view the Eclipse of the Sun next December?

The PRESIDENT replied that the Government certainly had not proposed any such measure, and were not likely to, but that the Council were now discussing the mode of application to Government, and the best way to derive results that were likely to follow from the observation.

Mr. STONE observed that he hoped that three observers might make observations on the polarised light, as two would probably differ in their results, and the observations of the third would be needed to settle the question. If anything had appeared to be settled by the Indian Eclipse, it was the question of the polarised light, which the observers agreed to have been polarised in a plane Pasing through the centre of the Sun, but the erican observations had again opened the

4 50

In which finally two atoms of potassium become substituted for two of the hydrogen atoms.

The sign is a remainder of the theory of types; it now is used to indicate that the two parts which it connects are H held together by the elements it points to. O mean H that the two atoms of hydrogen are held together by one atom of oxygen. In organic chemistry this modern notation is invaluable. Inorganic chemistry, however, can be taught just as well by means of the old notation. Still the former has its peculiar advantages, and will no doubt help to further the knowledge in that department as it has done in organic chemistry, where the constitution of bodies is so well studied that we can deduct almost every property from the formula. We can, with a certain degree of accuracy, predict the properties of a substance from its formula in inorganic chemistry, but not to the same extent as it is possible in organic chemistry. Here we derive from the formula the specific gravity of a liquor at boiling point, the boiling point itself. A well written formula tells us how many hydrogen atoms can be exchanged for a metallic atom, or for acid radicals. tells us at once whether the substance has more the properties of an alcohol, or of an acid, or of a base. It tells us, as we have discussed in our last paper, the specific gravity of the gaseous state and the quantity of heat necessary to raise the substance's temperature one degree.

It

It is evident that the chemical formula will not be perfect until it represents all the properties of matter as it does now a few. And when chemistry will make as rapid progress in the next twenty years as it has done in the last twenty we shall soon arrive at that perfection of our knowledge which Ber

However, the letters, and, if necessary, the horizontal strokes, are quite sufficient to make the rational formula of a substance perfectly clear. It is, as a chemist of high standing thollet thought to have arrived at some 70 years ago when he said, perfectly useless to attempt to give any other represen-published his Essai de statique Chimique. tative to the atom than its letter. Any drawing cannot but lead to too mechanical a view of the constitution, and we see in the present periodicals plenty of proof of the nonsense which such mechanical views, when used to too great an extent, will bring forth.

As the whole system of notation will become clearer by citing a few examples and discussing them, we append here an assortment of modern formulas and some explanatory notes as the conclusion of this paper.

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Hoping that I may have helped some of the readers of the ENGLISH MECHANIC to an understanding of the leading principles of the modern theory, I conclude my paper, asking the reader's indulgence for my want of style. I feel that have not the English language sufficiently at command to expose my ideas always so clear as I should like to have done.

EMIGRATION.-Professor Goldwin Smith writes to a friend in England a letter on emigration as a means of escaping the economical difficulties and perils which he fears are gathering round England. The professor commends the Southern States of America, especially Virginia, as better worth the attention of emigrating Englishmen than either Canada or the Northern States. He says, the Southern States are more English than any other portion of America, and that Englishmen in those States would find both a generous welcome and an ample field for their enterprise, neither of which are to be so readily found in the Northern States, where Englishmen do not and cannot iraternise with the Irish, German, or native American population. "In the Northern States" says Mr. Smith, "the English emigrant now finds himself, I am sorry to say, not only in a foreign but a hostile country. And as a practical and likely means of securing a solid home in Virginia, he mentions that there is a Virginian Land Company in New York, presided over by General Imboden, one of the Confederate Commanders-that he has had communication with the company and seen its papers, and that we are likely to hear of its movements in England. It should be added that he intimates that English predelections for Canada are a mistake, both on the grounds of climate and other natural and agricultural difficulties in comparison with Virginia and other

Southern States.

ROYAL NATIONAL LIFEBOAT INSTITUTION. -The annual meeting was held on March 15. The report stated that there were 220 lifeboats on the coasts, and that during the past year 871 lives had been saved through the Institution's agency. The sums voted as rewards had amounted to £2705, and 38 silver medals had been granted. The income, during the twelve months, had exceeded £40,000, and there was a balance in the society's favour of upwards of £6000.

LETTERS TO THE EDITOR.

[We do not hold ourselves responsible for the opinions of our correspondents. The EDITOR respectfully requests that all communications should be drawn up as briefly as possible.]

All communications should be addressed to the EDITOR of the ENGLISH MECHANIC, 31, Tavistockstreet, Covent Garden, W.C.

not letting it sink to the bottom of the vessel; place the vessel containing the above in a sand bath, and submit it to a temperature of about 90° C. (194° F.). Then take a retort furnished with a leading tube, which dips into the vessel in the sand-bath; place in the retort 540 parts of manganese dioxide (Mn.O), cover with hydrochloric acid, and apply heat Chlo rine will be liberated, and pass over into the solution

containing the baryta, which latter will be decomposed. Barium chlorate and barium chloride will be formed, and will co-exist in the solution together. The chlorine must be passed in until the milkiness has disappeared. More manganese may be required than is stated if the sample be very impure; but if 600 parts are taken, that will generally be found sufficient. The reaction which takes place may be

:

All eheques and Post Office Orders to be made pay- thus represented :able to J. PASSMORE EDWARDS.

I would have every one write what he knows, and as much as he knows, but no more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that, as to other things, knows no more than what everybody does, and yet to keep a clutter with this little pittance of his, will undertake to write the whole body of physicks: a vice from whence great inconveniences derive their original.-Montaigne's Essays.

CONES FLOUR.-BARIUM CHLORATE-TEST

FOR ARSENIC.-SODA CRYSTALS, &c. SIR,-On page 633 of your valuable journal a correspondent, siguing himself "One of the Old School," has expressed an opinion that my statement relative to the adulteration of cones flour with rice is incorrect. Now, we are aware that revet wheat is the proper wheat to use for the manufacture of cones flour; but I say that rice flour is wholly and partially substituted for that article, according as the price is intended to be high or low. Some bakers at Eton pay 36s. to 41s. per sack for good flour, and for cones from 20s, to 25s. I do not mean to say that 20s. is the regular price, because of course that varies; this flour, cones for dusting, as supplied at the present time here from 238. to 258., consists of nothing else but rice flour; and on applying to various bakers in the neighbourhood for a sample of cones, I invariably obtained pure rice flour. On one occasion I inquired minutely into the sale of this cones. and I found (a rice flour variety) that it was labelled "cones," invoiced "cones," and inserted in the account as cones. The bakers about here, as I have said before, pay 36s. to 41s.; and if they pay (now) 23s. to 25s. for cones, it is hardly likely that it can be pure wheat flour. Once, and once only, I obtained information to the effect that nearly the same price was paid for cones as for flour; and when it was found that there existed a cheaper variety, 268., it was obtained directly.

After having expressed my opinion on the matter from direct observation, I will take "One of the Old School" to a work called "Adulteration Detected in Food and Medicine," by Dr. Hassall, page 277.

Dr. Hassall says: "Dr. Paley, of Peterborough, brought a sample of flour seized on suspicion, and which the baker called 'cones flour. On subjecting this to microscopical examination, it was found that it consisted entirely of rice flour."

Page 279: "It appears therefore that cones flour is rarely to be obtained genuine, but is subject to an enor mons amount of adulteration; further, that some of the samples do not contain a particle of wheat flour, of which alone they should consist."

Twenty-two samples of "cones flour" were procured chiefly in the metropolis: the following is the result (this is also taken from Hasall's work). At the same time, I think it is a mistake to say that bean four is found in cones. The samples below, in which that article was found, were in all probability inferior, adulterated varieties of wheat flour:

1. Contains rye and rice flours. 2. Entirely rice flour. 3. Contains rice flour. 4. Contains rice flour. 5. Consists in great part of rice flour. 6. Genuine. 7. Almost entirely rice flour. 8. The same. 9. Chiefly rice and bean flours. 10. Contains much rice flour. 11. Not cones at all, but consists of rice, Indian corn, and bean flours. 12. Bean and rice flours. 13. Contains much

rice flour. 14. Contains barley flour and alum. 15. Genuine. 16. Barley and rice flour. 17. Consisting in great part rice flour. 18, 19, and 20 were genuine. 21. Not cones at all, consisting entirely of rice and Indian corn flours. 22. Consisting chiefly of rice, with some Indian corn flour and much salt.

Now, the preface to the above work is dated 1857, and "One of the Old School" will perceive he is decidedly behind time when he finds that Dr. Hassall found in cones flour that which I stated I found, in my letter on starch. I am glad to find he can "conscientiously affirm that no rice, beans, or any other intermixture ever entered a sack of his." He says that some of the "new school" add dry bean or white pea flour to wheat flour, to give it strength, but that "cones should consist principally of rice, and yet sold and accepted as cones flour is a novelty." We (all of us, I may say) read the ENGLISH MECHANIC for two purposes-first, diversion, the principal motive, and instruction the second. "One of the Old School" then must own that he has not subscribed for naught; he has gained a wrinkle, and that is, that rice flour is sold as cones, labelled and sent by rail as coues, paid for, aye, and the purchaser satisfied by paying rice flour price for CONES. Hassall says that there are several kinds of cones in the market, the best being nearly twice the price of the worst, the adulteration being usually in proportion to the price." I can tell. directly I see a loaf, which kind of cones the baker uses, real cones or rice flour.

BARIUM CHLORATE.-As there seems some difficulty in "Pyro" getting an answer to his query relative to the manufacture of barium chlorate, I will furnish him with the various minuti:-Take 918 parts of barium oxide (baryta), finely levigated, and suspend it, in water, keeping it in a state of suspension-i.c.

dioxide

(BaH2O2)6 + Cl12 = (BaCl2)5 + Ba (ClO3)2 + (H2O% The action of the chlorine being continued for a short time after the milkiness has disappeared, the clear liquid (if necessary) may be filtered, and the filtrate added to the residue, the whole raised to the temperaevaporated to dryness. 2000 parts of water are then ture of 10 C., and set aside to cool; the barium chloride will remain in solution, and the chlorate crystalsing out. 316 parts of this latter salt would be formed by taking the above quantities.

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20 x 10

8

W= load, equally distributed. 1, length in terms of depth, s, strain of compression at top flange, or Wxl tension at bottom flange. S = Now, 10 tons placed upon the centre of the girder in question will be equivalent to 20 tons equally distributed. Hence, the formula becomes 25 tons strain at centre. The breaking weight of this girder may be found by the following method:-Let a = sectional area of bottom flange in inches, d depth in inches, and s = span in inches. 744 tons a constant for wrought iron girder or tube. = breaking weight in

8

HYDROFLUOSILICIC ACID.-"Taffy," although professing to correct me in the barium chlorate preparation, has failen into an error himself with regard to the above acid. "Pyro" can prepare it thus-Take one part each of finely-powdered fluor spar and powdered glass, or fine sand, and mix with 6 parts of concentrated sulphuric acid (H, SO1). On applying heat to the mixture, gaseous, silicon tetra-fluoride is formed: (H2SO4)2 + (CaF2'2 + SiO2 = (CaSO), + SiF1 +(H2O)1⁄2 A precipitating glass is then taken and partly filled with distilled water. Some mercury is then placed in the bottom, and the tube delivering the silicon tetrapasses out of the mercury is decomposed by the water, fluoride is made to dip into the mercury; the gas as it forming gelatinous silica and hydrofluosilic acid. This latter is not "a gelatinous mass," as "Taffy" states; the silica may be separated' by filtration through a cloth, while the clear liquid is hydrofluosilicic acid (H,SiF). This acid, when concentrated, fumes strongly in the air; when added to potassium chlorate, an insoluble potassilicon tetrafluoride is forme d, bottom flange area of 6in., then liberating chloric acid. This chloric acid solution may be poured off the insoluble precipitate and neutralised with barium carbonate, and followed out as Taffy" states. The following reaction takes place on passing SiF, into water:

(SIF) + (H2O)1⁄2 = SiO, + (H2 S Fo1⁄2 PURIFICATION OF CHLORIDE OF SILVER." W. H." will find that heat is the proper method for separating paper from his silver chloride. If he dissolves the chloride by means of ammonia, he must recover it by spontaneous evaporation. If he attempts to drive off the water by the application of heat, he will find that fulminating silver will be deposited. I merely mention this because I find "Ernest and Beta" had both forgotten to mention it, and W. H." instead of recovering his chloride, might lose his head. The excess of ammonia might be neutralised by the addition of an acid before evaporation.

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TEST FOR ARSENIC.-Let "Claudius" proceed thus:-Procure some pure zinc. free from arsenic, and place it in Marsh's apparatus with the substance to he tested. Add sulphuric acid, and when the gas is being given off freely light it, and hold a crucible lid in the flame; if arsenic or antimony are present, there will be a metallic deposit upon the lid. To discriminate between antimony and arsenic, the metallic deposit must be submitted to the action of a drop or two of yellow sulphide of ammonium; antimony dissolves, and arsenic remains unaltered. To test the cleanliness of the apparatus, use the zinc and sulphuric acid alone. If clean (free from arsenic) and the materials pure, there ought to be no deposit upon the lid. Arsenic may also be detected when in solution by giving a green precipitate with cuprammonium sulphate. The precipitate consists of arsenite of copper.

POWDERING PHOSPHORUS.—“ M. P. S." can reduce phosphorus to an impalpable powder by dissolving it in bisulphide of carbon, and letting the latter spontaneously evaporate. By-the-bye, I may as well add that the latter operation is best performed in the open air, if the operator is blessed with the sense of smelling.

tons at centre.

44.64 tons.

ax d x 744

8

Let the girder in question have a 6 x 24 x 74.4

=

240 ROBERT PICKWELL.

QUESTION FOR MILLERS. SIR,-In answer to "C. J.'s" personal question, I beg to say I have only in one instance had the trouble he complains of with the neck of the stone spindle, which happened some time since in a mill I was carrying on off-hand, when I had to take the stones in hand myself, and flayed two high sides of the bedstone, and when I had dressed them two or three times myself the neck went all right, and has been no further trouble the last two or three years. I will also add that I rectified the running balance at the same time.

To the second question, I never yet saw a thick top heavy stone running satisfactorily on a short spindle, and I have always kept the greater part of the weight of the stone below the bearing in my own mills, and shall continue to do so. Some years since one pair were fitted with universal iron, like the ship's compass, with the bearing near the face of the stone; but they had to be removed and replaced by cross bar and driver.

R. R. SMITH

REFLECTORS AND REFRACTORS. SIR, It is nearly eight months since I last wrote to you on the above subject, and I then promised your readers, should they so desire it, to supply them at some future time, with a further description of the 84in. mirror and its performance. Froin the kind allusions which some of your correspondents have made to this promise of mine, and to the matter contained in my former letter, and from the increasing interest with which, I am glad to say, the subject of practical astronomy is every week being invested in your columns, I feel I cannot do better, during a period of enforced rest from professional labour, than state what I have found that performance to be, and drop some further hints to amateurs, who, like myself, are anxious to render their home-made telescopes as perfect and useful as possible. I had thought of giving a brief résume (with the Editor's kind permission) of the work done during the past half-year, but found it would occupy far too much space and trespass too much on your indulgence, to think of such a thing, so I shall simply state the work done on one or two favourable nights last summer, and leave the reader to form his own opinion of what the telescope has since accomplished on similar nights.

SODA CRYSTALS.-In the manufacture of soda crys tals, the first step is to form a sulphate of soda. This is done by placing a quantity of common salt in a decomposing pan, and running in an equal quantity of oil of vitriol. When heat is applied, hydrochloric acid is given off, and may be condensed in towers or scrubbers. The mass is then raked out upon the hearth or roaster adjoining the decomposing pans, and submitted to a somewhat higher temperature. A short time after I had written the former letter. The salt-cake thus produced is mixed with an equal describing the mounting of the Shin. mirror, which I quantity of limestone and two-thirds its weight of had obtained from Mr. Browning, of the Minories, in coal. A charge of this mixture is introduced into a reverberating furnace, heat applied, and when comthe end of June or beginuing of July, we, in this neighbourhood, were favoured with four nights in pletely fused it is raked out into moulds. This product succession of most exquisite definition, a boon indeed is called black ash. This product is digested with to those who possessed really good instruments, which warm water, the clear solution evaporated to dryness they wished to test. On the first of those occasions, and heated with sawdust, to convert any caustic soda in the early evening, just as the sun was setting, I into the carbonate. The residue is then dissolved in brought out the large telescope, and having inserted a hot water, decanted off from any insoluble matter, large field eye-piece, giving a power of 35, and a field and run while hot into crystallizing paus. After the of 34 degrees, directed the telescope to the position in first crop of crystals have separated, the mother liquor the sky where the planet Saturn would probably be is drained off, and evaporated for a second crop. Does found. After some little searching, I successfully Soda Crystals" infer that his decomposing paus hold 120 gallons, or that that is the capacity of his picked him up, shining with a pale silvery light, in s crystallizing paus? If the latter, they would hold sky which appeared, with that power, of a deep violet lue. Viewed under such circumstances with a large 160wt. of soda crystals, deposited from solution. By a little calculation he will be able to arrange quanti-telescope, and with the evening light still bright, the planets present a most beautiful appearance, one tities in the proportions given above that will suit his which often tempts the observer to neglect for a time plant. the use of higher powers, but of course, if the physical details of celestial objects are to be investigated, they must be used.

"Practical Chemist " (Query 2051) is easily answered. There exists no acid termed “hypochloric" acid. Hypochlorous acid is known, having the following molecular formula, HCIO.

GEORGE E. DAVIS.

The definition I knew to be most excellent, for, with a little experience, one look at the circle of light which is formed in the eye-piece, when a bright object.

H.

RECENT QUERIES AND REPLIES FROM
MILLERS.

I main

SIR, Mr. J. Sharpe, in answer to several correspon
dents, denying that I am the inventor of the universal
joint, described on page 526, No. 255, says that he has
had the same working in his mill since 1856, while the
description he gives of it seems to represent quite
another thing.
Perhaps Mr. Sharpe will be kind
enough to send a drawing to your excellent engraver
of what he means by the following sentence:-"The
oval ring of mine has the journals at the foci of the
transverse dia., which admits of the inner ring, or
driver, being shorter, and therefore stronger, and
leaves more room between them"-without which the
following sentence seems quite incomprehensible-
viz., that the centres of all his journals are in the
same circle, which could not be so in mine.
tain that the centres of my invention are in a circle;
therefore, if bis joint is anything different to this, as
he says, all his centres cannot be within one and the
same circle. My object in forming the oval ring was
to bring all the centres within a circle, so as to cause
the stone to oscillate alike on all the four bearings.
The centres are also in the same plane or level. It is
therefore a perfect universal joint in every respect, and
as it stands is purely and simply my own invention.
I also repeat my former assertion that it is superior
(until convinced to the contrary) to anything at pre-
sent in use. May I invite Mr. Sharpe to send to the
MECHANIC the first new thing, as he deplores so much
the antiquity of all hitherto sent respecting milling?
THOS. EVANS, Stockport.

shoddy manufacture. Tat used for opening raw cotton is called the willow, which name he makes use of, but that used in the shoddy manufacture is called the willey. Now, the willowing or scutching machine, is composed of a feeding apron and two sets of rollers and beaters. The first set of rollers, turning in opposite directions, drag the raw cotton through, and transfer it to the first pair of beaters, which, revolving with great rapidity, thrash out nearly all the sand and other impurities which the wool contains; the second pair of rollers and beaters complete the process.

GITCHE MANITO.

METEOROLOGICAL.

SIR,-Would you, or some one of your readers, give information how to observe the daily changes going on in the horizontal and vertical motion of the needle, as well as the intensity of the magnetic force?

Is there not some more simple way of observing and recording these variations and earth-storms, than the complex apparatus in use at some observatories?

J. W. A.

THE ILLUMINATED PORTION OF THE MOON.

is slightly out of focus, will tell this, if the illuminated the components of this star are only 0-55 apart, and erele is steady and calm, without any bubbling or it was with fear and trembling I approached it on the waving motion, after the telescope has been for some first night, but what was my joy and delight, when I tome in the air, the observer may prepare for good had applied a power of 300, to see the discs clearly work This steadiness, too, is not in the least affected separated by a black division, yet looking square! by the beautiful pulsations of coloured light which When, however, I had applied a power of 350, the cesar from the larger stars, but refers equally to them. division was perfect. Again and again I looked at It was peculiarly so on this ocession, for having this beautiful object, two 8 magnitude stars, like most inserted, first a power of 100, and then, as the evening minute circles of light, lying so exquisitely close to darkened, 157, I was enchanted and completely chained one another yet perfectly distinct. I thought I to the spot with the exquisite appearance of the planet detected a slight difference of colour in the comSaturn, without one trace of haziness or of indistinct-ponents, and hope, when the calm summer weather ness of outline; it seemed chiselled out in colours of comes again, to make many more observations on this It will thus be seen that " Scrutator" has jumbled purest silver and pale sky blue, and golden yellow, star, for a most wonderful and interesting object it together the two machines, owing to the similiarity The dark division in the ring was sharply marked all certainly. of the names; "rushed headlong into print," to use his round, without a break in its continuity, spreading While speaking of this star I may mention, that it own expression, without taking taking the trouble to out into a dark band at the "anse," and narrowing at scems somewhat more easy to divide than 7 Andro-investigate and thoroughlymaster" the subject: the minor chord of the ellipse into an infinitely fine meda, which I have nicely separated on some favour- has drawn hasty conclusions, and tried to criticise black line. The transparent ring too was so evidently able occasions since; perhaps this may arise from the what he apparently knows nothing about. and beautifully seen, of a dusky grey colour, and greater magnitude of the latter. 4 will finish what I clearly less bright on the side next to the rings, than have to say on the subject next week. on that next the planet. This I took particular note of, and examined it most carefully on the two following evenings, when it was verified beyond all doubt. It is not noted in the engraving of this planet in the interesting little work by Mr. Lockyer, copied from Mr. De La Rue's sketch, but is very well marked in the lithograph on the frontispiece of Mr. Browning's pamphlet. On the occasion above mentioned, it was plainly seen, not by myself alone, but by two other gentlemen, who were examining the planet with me, We also directed our attention to the outer ring, and searched with the greatest care for some trace of a division, but could not detect any line which might be rightly so called; there was a shading sometimes visible, more guessed however than clearly seen, which might possibly suggest the idea, but did not satisfy me. During the time I was observing the shading on the transparent ring, and searching for a division on the outer one, five of the satellites had come into view. On the second evening I saw the sixth, and had glimpses of the seventh if it was not a very minute star, for not having any ephemerides of the satellites, I could not absolutely identify it), with the six satellites however, so clearly seen, and the body and rings of the planets so beautifully defined, your reader will believe me when I say, I never saw a more wonderful or more fascinating object. There was one thing about this strange planet which delighted me, even more than all I have yet described. I refer to the colours on the ball and on the rings-it is only on such nights as these I am speaking of, that this phenomenon can be seen to any advantage, and to see it well a large aperture is absolutely necessary. I do not know how most astronomers account for these colours, whether they think them intrinsically inherent in the planet or its atmosphere, or to some extent caused by the vapours in our own atmosphere, through which the light of the planet has to penetrate, certain it is that they are much better seen and brighter, when the planet is near the horizou, provided only SIR-Without any wish to find fault with other high powers can be used, than when it is more over- suggestions, I send you a description of a band of head. I believe, too, the larger the aperture the more simple and cheap construction, and of the efficiency clearly are they marked, so that the possessors of large of the action of which I have had several practical telescopes have a very great advantage in this respect, proofs, A strip of copper and one of zinc, of any over those who are not so fortunate. On the night in desirable length, are to be joined (by rivet or any other question, I found that a power of 350 showed them preferable mode), at the ends, the joint whipped most admirably in my reflector of 8in. I could well together by thread, and varnished with shellac in imagine, however, the much greater brightness and alcohol; the extreme ends having a hole punched in I do not know whether Sir John Herschel will be beauty they would have in a 121n, or 15in, speculum. each, for fastening with a silk ribbon, or ether non-considered au authority with that gentlemen; he proThe contrast between the delicate sky blue of the conductor. To apply and bring the same into action, bably will be by most of your readers, and I therefore poles of the planet, the golden yellow, alternating wind a piece of list spirally round the united strips of beg to quote from his "Outlines of Astronomy" in with silver and grey on the belts, and the blending of metal, wet the list with vinegar, reduced in strength conclusion:-"The sun's distance being 23984 radii all these hues on the rings, was indeed a lovely sight, by water if slight action only is wanted, cover the of the earth, and the moon's only 6-the former is but should be looked for and seen to be at all appre-wetted list with oilskin, and fasten it with the ribbon nearly 400 times the latter lines, therefore, drawn ciated. The beautiful appearance which Saturn pre- in desired part. About an inch of each extremity of from the sun to every part of the moon's orbit may sented on that occasion, lingers in my mind still, and the strip of metal, must be left uncovered at each be regarded as very nearly parallel." although I have seen the globe of Jupiter under end, and be in contact with the skin. The cost of the equally favourable circumstances, with far more contrivance must evidently be reckoned in pence. marked and darker hues on his belts and brighter tints SUFFOLK AMATEUR. altogether, the soft delicate beauty of the planet Saturn surpasses in perfection and loveliness all else I have ever seen in the infinite amplitude of space. I have dwelt thus minutely on these observations of Saturn, because they have made a lasting impression on my mind, and showed me what a perfect speculum will accomplish under favourable circumstances. But to continue my description from my note of these evenings.

The planet Saturn is setting, and at last drops behind the roof of a neighbouring house, so I am reluctantly compelled to turn the telescope to other objects, and surely here are a great variety of most interesting double stars, some of them excellent tests, and all very favourably situated for observation. Here is Aquilæ, à Ophiuchi, Ophiuchi, Cor, Bor., & Cygni, 2 Bootis, all just as well placed as they could be. Here are also two remarkable nebulæ, M 67, the annular nebula in Lyra, M 13, the maguificent globular cluster in Hercules. Let us take them in the above order and give you our impression of them as we saw them on those admirable nights.

Aquile. I have divided this star more beautifully With a 2 Sie. achromatic, by Wray, so of course do not mention it as a test for an 8in. speculum, but certainly the smallness of the discs and the large space between them, does surprise one who has been accustomed to telescopes of much smaller aperture; a power of 100 separated this star well.

Ophiuchi, Ophiuchi. The former a beautiful Objet, both easily divided; components with exquisitely small discs.

GALVANIC BANDS.

SIR-When I called your attention to an apparently anomalous appearance in the illuminated part of the moon, it was with the view of affording or eliciting information for the more observant of your readers. on a subject which probably has puzzled many of them, but I had no idea of its being so followed up or for so long a time. When the letter of "Sigma" appeared, I thought his satisfactory explanation would have been generally accepted, and though I think his diagrams might have been improved, I forbore to trespass more on your space, or to tax your engraver further. But as Mr. Beardsley cannot accept the explanation of "Sigma" and has sent you a diagram, I cannot help writing a few words on the subject, especially as his diagram is pretty nearly what I would have sent myself, and helps to prove "Sigma's " views instead of his own. If any of your readers will place a pin to represent the position of an observer on the earth's surface where Mr. Beardsley supposes him to be, another lin. above it to represent the centre of the moon, and a third at a distance of 33ft, in the direction of Mr. Beardsley's retiring suns, and to do duty for one of them, the relative positions of the three bodies will be nearly obtained; a thread then passed round all will show how very nearly parallel the rays of light from the sun to the earth and moon are, and thus prove the contrary to what Mr. Beardsley puts forth as his argument against Sigis directly opposite the sun, although the latter ma's" explanation. The enlightened part of the moon appears on the tangent to the earth's surface shown by Mr. Beardsley.

R. L. J.

DR. TYNDALL'S EXPERIMENTS ON LIGHT. SIR, On trying the experiments on atmospheric dust particles, of which an account appeared in your journal, it occurred to me to try the effect of inorganic mis-particles, and for this purpose a piece of brown paper was ignited, and allowed to smoulder for a short time in the darkened room. A very small quantity of romarkable and unexpected degree, and on a spirit smoke (carbon particles) heightened the effects to a lamp being held four or five inches below a beam of sunlight, the apparent cloud of smoke, before faintly An iron bar, seen, was now strikingly manifest. raised to a red heat, showed the same effects.

SELF-CENTERING LATHE CHUCK.
SIR, I think that "A. B." must have made a
take in his drawing of the self-centering lathe chuck
that appeared in your last issue. I see that the thread
the mandrel. Now, I have seen a great number of
is left-handed in the chuck, where it screws on to the
chucks, and have used them myself, but I never before
either heard of or saw one with a left-handed thread;
directly the tool in the rest commences to cut the
piece of work fastened between the dogs, the chuck,
instead of tightening up on the mandrel, will
screw off, unless the cut be a very small one; but if
tighter the chuck would get. One with a left-handed
it was a right-handed screw, the larger the cut, the
screw might answer for a face-lathe, or more com-
monly called a chuck lathe, where by twisting the
belt, the lathe can be reversed, and uit the idee
rest at the opposite side to where it is usually used. I
think the chuck, on the whole, is a very useful one, it
saving a great deal of trouble in setting small work.

MARINE.

ARTIFICIAL ICE.

S. T. PRESTON.

SIR,-In a late number of the ENGLISH MECHANIC

inquiry was ma le where aramonia apparatus for the production of ice could be obtained. I have one proParis, and have used it with perfect success several cured from Mignon and Rouart, 149, Rue Oberkampf, times. Some friends have had one in constant use for four years, and it never required repair or renewal of any sort. There are two sizes for domestic use. one costing 282f. or £11 6s., makes one kilogramme of ice in about two hours with the expenditure of about-a double handful of charcoal, and pint of methylated spirit or less. The other makes 2 kilogrammes in 3 hours, and costs 4061., or £16 58. There are larger for manufacturing purposes.

J. B. YONGE, Mebourne, Winchester.

COLLIERY VENTILATION.

SHODDY MANUFACTURE. SIR,-Seeing "Scrutator's" remarks in No. 258, page 610, on the way in which I endeavoured to help one of your correspondents with regard to the shoddy manufacture, I was at once induced to look further into the matter, and have since consulted one of our best encyclopædias on the subject. In this work, I Crgui. A much more difficult object for a reflec- used for tearing up old woollen rags, &c.—“ Serufind that I am perfectly correct as to the machine tor than any of the previous stars, as it is of the third 19 tator magnitude; however, on three of the evenings referred chine mentioned to be correct as I take it, I bave goes further, and says, that allowing the maSIR. As a well-wisher of the ENGLISH MECHANIC, to it was beautifully and completely divided, and only mentioned one of them, and therefore 1395 is and as I desire to see its usefulness extended, I beg to frequently since that time, whenever the air was fine still unanswered." and steady, a power of 187 just split it, but 300 comAs far as the shoddy is concerned suggest that colliery ventilation would be a good pletely divided it. The division of this star gave me the willey is the only machine used to reduce it to a subject for discussion in its pages. You would thereby state fit for spinning. To go further into the matter give some of our most intelligent working men an very great pleasure, especially as it was accomplished would be to give an account of the machines used in opportunity of recording their experience and giving so easily and so neatly. spinning and weaving, &c. "W.M," the correspondent their opinious. who asked for the information, is apparently satis fied; therefore, what business is it of Scrutator's to criticise that which is meant for others?

7 Cor. Bor. Very easy. 187 completely divided it; dise beautifully defined and exceedingly minute, with 30, black division was equal to 2, if not 3, diameters of one of the discs.

pBootis. Here was indeed the crowning test, as

The willey, which, he says, is used for opening raw cotton, is quite different from the one used in the

To begin, would any brother reader oblige me with an honest reply to the following query:-Query; If the intake of a colliery should be 50ft. area, what should be the size of the return-with the mode or rule by which it is found? T. H. THOMAS.

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WHEEL-CUTTING ENGINE.

the boiler, which cannot be tampered with whilst the, steering a screw-vessel under canvas, with her pro latter is working, continues to blow off steam, no mat-peller down, especially if it be a three bladed one. ter how heavily the lever of the large one may be This is entirely obviated by the self-feathering screw, as the blades, when feathered, offer no twist to the GEORGE BATES,Agent for Messrs. Hopkinson and Co., passing water. for Durham and Northumberland.

weighted.

SIR,-Through the kindness of a gentleman at Halifax, I am enabled to forward a very good photograph of a wheel-cutting machine for small work. BB is the bed, which is solid towards the left-hand end, and open to the right, to form a slide for carrying the upright part QEF, which is drawn along by a screw, of which the handle appears at H, to adjust for different diameters of wheels to be cut. Supposing the FOTHERGILL'S SELF-FEATHERING SCREW

slide R R to be taken away, and W the wheel to be cut, the upright slide would first be brought to its place by turning the handle H, next the set screw C loosened, and the peg under it slid down to the circle of holes containing the division to be cut, and the peg of the alidade A brought to the same circle by sliding along the pin P till the index at I shows the right number. The stops SS are then adjusted, so that the lever TV, which works on a loose socket at T, may be able to swing sideways to the amount of the angle subtended by each tooth of W; and the machine being set going, the first cut is taken downwards by depressing the handle L, which may be made to rise again by hanging a weight to it over a pulley fastened to the ceiling. To move the division plate the required quantity for the next cut, the peg under C is first lifted by raising the end V of the spring lever TV against the pressure of the spiral spring D, and TV is then moved towards the right till it is stopped by S; and on letting go the lever the spiral spring D forces the peg at C into the proper hole in the plate. Next, by pressing on the head of D, the lever N presses against another lever (O) under the plate, lifts A up out of the way, and allows the plate to be moved round till TV comes in contact with the other stop S; and so on for each tooth in succession. M is a micrometer for adding a tooth when the division plate does not contain the precise number wanted- as, for example, in cutting 101 teeth with a division plate of 100 holes.

For bevel wheels the quadrant Q allows the upright slide to fall forward to any required angle, and for cutting teeth askew, as in the case of a worm-wheel, there is a centre at E on which the vertical slide can be swivelled over sideways. K is a hole in which a crane may be fixed to come over to steady the top of the arbor on which the work is held.

The picture shows the arrangement for rack-cutting, the whole length of the slide R R being itself a rack, into which the wheel W works. The lever L is found to work more agreeably than the screw which used to be at the top of F for moving the upright slide. J. K. P.

HOPKINSON'S VALVE. SIR,-In reply to the inquiry of your Leamside correspondent of last week, I beg to inform him that the two valves act quite independently of each other; and the small one being regulated by a dead weight inside

PROPELLER.

SIR,-The above screw is designed to supersede the necessity of hoisting up the screw in auxiliary screw vessels, when under canvas. It is entirely self-acting, requiring no hollow shaft or inside gearing, as in the case of the Bevis feathering screw; all its parts are concealed, so that no wreckage or floating material can jamb its action, its external appearance exhibiting no more peculiarity of form than an ordinary propeller. (Fig. 2.) The principle is equally applicable to any kind of screw, whether two, three, or four

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blades. The boss is divided into three parts (Fig. 1), the forward part carries the blades for going a-head, the after for going astern, immediately upon the engines stopping or upon the vessel over-running or outsailing her screw, the blades feather themselves into a line with the keel, and become useless. In regard to stowage of spare screw, and repairs of damaged screw, it has many advantages over the solid propeller, as its parts can be stowed separately, and a broken blade or other part re-supplied at once from the spare screw. All seamen know the difficulty of

It is anticipated that, now that the opening of the Suez Canal will render auxilliary steam power of more necessity than ever, that a screw on the above principle will be found a useful invention, especially in short-handed ships; and in all, when the expense and room of the screw-well may advantageously be

avoided.

which can be seen on application, by letter or other The inventor has a 10in. in dia. model in gun-metal, wise, to Watford,, Crick Station, near Rugby.

F..

HEATING GREENHOUSE BY GAS. SIR,-In reply to D. Bothroyd (Qy. No. 2067), I beg to state that the consumption of gas for heating the water-pipes in the greenhouse alluded to in No. 1708 has again been accurately tested by a dry meter (Glover, maker), and found to be 25 to 30 cubic feet per hour, according to pressure, which varies a good deal, and which is a very great disadvantage in the use of the most economical burner-the atmospheric-as so much depends on the proper proportions of air and gas previous to ignition so as to ensure as complete combustion as possible, and so prevent smoke or deposit of carbon. At 38. per 1000 cubic feet, the cost of gas in Bath, this is under 1d. per hour; and this winter, with the thermometer at 19° out of doors, the temperature inside the greenhouse was 46, at least 60 higher than required to keep the frost out. With the apparatus of Hertsman, of Bath, it could probably have been kept steady at 40, when the expense would not have averaged d. per hour. This very much coincides with the result of what "Professional," of Brighten, gives as his experience (see ENGLISH MECHANIC, page 637); only had he used 4in. instead of 3in. pipes, his quantity of heated water being larger, probably his result would have been in proportion.

Where there is no regular gardener or male domestic on the premises to attend to the fire of a flue late and early-for it is hardly work suitable for a female to feed either with coal or ashes-the gas (with an atmospheric burner properly fitted, and supplied with suitable mixture) will not only be found in every way more suitable, but cheaper. A man up at 12 and 4 a.m. is not long fit for his usual day's work. If the common gas-burner is used, the expense will be very much greater, and the result less.

Can Professional" give the address where a simple good gas pressure gauge, to be attached to the meter, can be obtained? This would be of much value to consumers generally.

A very simple and cheap method of keeping frost out of a moderate-sized greenhouse is by an Arrot stove of the right sort, with an upright pipe of in., by

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