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described Myers's patent reods mero than once—see No. 262. Tiie Phvsharnionica "Med with a swell," has also been described in the English Mechanic to be a free reed combined with a pipe.

I believe the Germans put a 2ft. pipe to a tenor C reed, but it is obvious the pipe may he shortened to half, to a quarter, to au eighth, or even to a sixteenth of that length, whieh would approximate to the length of the wind channels for such a reed in the harmonium. We have Mr. Herman Smith's authority for regarding all these wind channels as veritable pipes. I infer the shorter the pipe the greater the influence of the reed on the short column of air within it, and of course the less tho influence of that column of air on the sound of the reed in the way of improving its timbre.

"Alexandra" asks for a trumpet stop in the barnioniura worthy that title. I can't help hor, unless she can find room in the instrument for more pipe tone < along with the reed tone) than any short wind channel can bo expected to afford. Ill Bueh case, we at onoe introduce a rank, whose wind channels are so lcug as to take it quite out of the harmonium family. It may he said there is no natural line of demarcation between wind channels and pipes—lmt u double C reed, with u 'wind channel or pipe 4ft-, or even 2ft. long, would rather come under tho category of aa organ rank, than an harmonium stop. "Alexandra" would cheaply obtain much information by reading} the patents mentioned in " Harmonious Blacksmith's" reply (also intended for her) to "J. C. P. ;" in No. 277.

Referring again to the significant fact that none of 4he harmonium makers have offered the least assistance to "Alexandra" for contrast and variety of tone, it may be that those who have mastered the details of mere ordinary construction fear absence of adeqvate pecuniary reward, for spending time, money, and brains in the construction of an instrument very much out of the common way. Who can blame them while they can sell their productions? They have their living to get, and this takes a great deal of the poetic feeling out of us.

W. T., Pianoforte Tuner and Repairer.


[225] Sib,—Yonr correspondent "C. C. S," in his reply to " Sabbas," refers to a new student's microscope exhibited in the Workmen's International Exhibition as being suitable for his requirements. I have much pleasure in oorroboretnig "C. O. S.'s" statement. Having worked with the instrument I am fully convinced that it is the cheapest microscope in the English market. The stand iM made uf one solid piece of brass, whereby great firmness is secured; it has a Bprifig object-holder, a good object-glass, the eyepiece is excellent, the rack work and fine adjustment smooth and easy. In fact, it form* the basis of a very capital instrument. Wishing your greatly improved journal increased success. F. IS., F.R.M.S.

[" F. B." stated the price of the above microscope, which we omit for reasons given elsewhere.—Ed.]

suggestion in the way of increasing tho circulation, I hope that others, who may feel inclined, will make other suggestions, so that we may all unite together to increase the prosperity of the English Mechanic.


[Other correspondents have expressed themselves similarly to "Hopeful." Mr. Grierson, who has so valiantly defended the Lewis system of shorthand, says:—" I always leave my English Mechanic on our othec table for some time, for the benefit of my fellow students. One of theni has just become a subscriber, and a second states that he intends to become one." Q. Sea says in a letter:—"I take every opportunity of introducing to the notice of my friends us the most friendly act I can do them."—Edj


1.226] Slu,—Though I agree with the "Harmonious Blacksmith " (letter 213, p. 496), about enlarging the size and increasing the price of the English Mechanic, I think the plan suggested by you is by fur the best, if it can be carried out. You know best. At all events tho offer is both a generous and courageous one. Our facetious friend, the "Harmonious Blacksmith," suggests that the English Mechanic should be increased eight pages in eiae and one penny in price. You, air, say you do not know what the ultimate size of the Englibh Mechanic may be; and judging from the manner in which it has incorporated other periodicals of late, it would not be nn easy thing to foretell. But you say distinctly that you have no idea of increosingthe price, though you will increase the size eight paget if you could get three subscribers where you have but got two. Here then is, as I take it, a bonafiile offer, and onothat reflects great credit on the management. It is in fact a challenge, and I beg to suggest that we, the subscribers, take it up at once and heartily. I believe that our subscribers may he increased onethird with comparative ease. Not one-half,'.I may say one-third, of the people interested in such a publication as ours, tako it in at the present time. I am just returned from a short holiday trip, and I was surprised in several instances to find persons, and just the ones to become subscribers, who knew little or nothing about the English Mechanic: and I have reason to believe that two or three of them, on their return home, will become subscribers. I know no better way to widen the area of our readers, than for those who are suhicribers to introduce the j ournal to strangers during their holiday trips this time of the year. In nioro than one instance I left my copy at the hotel, in the smoking-room; and I was interested to see how it was looked into and enquired after. I bog to suggest that others do likewise.

Our ever obliging adviser, "F.R.A.S.," said (page iil2):—" I assure you I jiersonally recommend the English Mechanic right and left to every scientific friend I have, and to others, who, without claiming any title to that appellation, yet wish to know what is going on in the way of physicalaud mechanical discovery." If '' F.R.A.S.," who takes so much trouble to enlighten as, also recommends our journal "right and left," certainly we, the mass of the readers, may imitate hiui in one way at all events, by recommending our friends "right and left" to become subscribers.

I, for one, sir, will take up the challenge, which you Itave so courageously made, and as I have made one


[227] Sin,—"Snburban"rebukesme(inangoodteith I know), for what I do as a duty, and not a pleasing one. The readers of the English Mechanic have a right to claim that thoso correspondents who are familiar with a subject should not suffer erroneous statements respecting that subject to remain uncontradicted. Personally I should care nothing though "A. Z."chose to assert that the earth is corkscrew-shaped, or thongh "B. Y." sold that Jupiter is a pancake; but if they assert the theories in the English Mechanic I should not hesitate to point out that on the whole accepted views are preferable. It is not the shortcomings of "A. Z.," or "B. Y.," or "C.X.," that I regard, but the injury their- mistakes may do to oar journal. But is "Suburban" serious? He speaks of "unlucky mortals " who are " in the wrong," and who "happen to assail'' people, almost as if he loved them, and he will not have them "transfixed with an epithet" at any price. Are they worthy of "Suburban's " championship?

Has not our own "F.R.A.S." lashed some of these offenders, and stingiugly, too? I once called in his aid for snch a purpose, and I remember it was very effectual indeed. B. A. Proctok.

THE FLUTE AND FLUTE PLAYING. [228] Sib,—I am an old man—a musician—and in my youth used to play tho flute. I have heard Drouet, Nicholson (in his prime), Richardson (an old friend), Pratten, (ditto), and most of the later performers; and am also an amateur mechanic, and conseqnentlv an admirer of your publication; but little did I imagine that I should live to see any arguments in favour of that detestable instrument (tho flute)— fit only for mild curates and similar-minded individuals. I know all about the abortion, have seen overtures arranged for four flutes, and have had to accompany solos performed on an instrument with eight, andheaven knows how many more keys. Also, I once heard Boohm, and after that, nothing that I have heard, or ever shall bear, will convince me that the flute is a desirable instrument for any one to waste his time in learning to play. I once gave an engagement to Richardson to play at a concert, being anxious to do him a service. On the night he sent me a notice, saying that a frail in his cheek made it impossible for him to appear. Fancy tho situation—poor fellow: Read in any old novel the description of a curate's ubodo—" Over the mantelpiece, on two books was placed his flute, 4c." But, with nil my prejudice,

I will say, that for tho true poetic "flute-like" tone, nothing surpasses the old German flute; and I shall bu much surprised if our facetious and learned friend, the "H. B.," does not agree with me, at all events, in this particular. F. F. C.


[229] Sie,—Searching through Shaw's "Boyle" for information relative to an experiment conducted by Boyle, I happened upon a paragraph (Vol. ii., p. 451) containing a statement so incredible—at least so it appears to me, although founded on the observations of two eminent men—that I venture to claim the assistance of yonr readers in an endeavour to arrivo at the truth." I will now proceed to quote, so far as is material, tho paragraph in question. After stating that, perhaps, tho atmosphere may rise to the height of some hundreds of miles, Boyle says: "Nay, exhalations may ascend much higher, if there was no mistake in that strauge observation made at Toulouse, in a clear night in August, by the diligent Emanuel Magnan, who, as Ricciolus tells us, 'saw from

II o'clock at night till 12, whilo the moon was under the horizon, a little lucid cloud, near the meridian, and almost in the zenith, which could be illuminated by nothing but the sun; and, therefore, must have been hi"her than the whole shadow of the earth. And,' says Ricciolus, 'the like phenomenon was observed by the great mathematician Faeeius.'"

Now, beyond the short explanation contained in the paragraph above quoted, I am unable to ascertain what were the observations made by either Emanuel Magnan or Riocius; yet, I cannot but think that the observations in question must have been founded on error; since, if we suppose the cloud to have been higher thou the whole shadow of tho earth, then its distance from the observers considerably exceeded half u million of miles; oud if, as we may suppose, the cloud was at that distanoe of visible sensible breadth, then it must have had an actual linear surface of thousands of square miles. That such should have been (he actual case appears to mo improbable in the extreme.

However, it is probable that the cuormouB circle of readers of the English Mechanic embraces more than one student of science familiar with the labonrs of Magnan and Riccius; and, I doubt not, their kind assistance will soon remove my difficulty. Should information as to the above-nientioued phenomenon, however, be not foBtheoming, then, sir, you or your readers will, perhaps, favour with uu answer to the query forming the heading to this letter.

Glaisher has, I think, Htated that when at the greatest altitudes, the cirrus clouds, commonly called " mare'stail." appeared to bin to be dtetsnt as ever. But what I wish to know is, whether or not exhalation;-; ascend beyond the earth's atmosphere. S it.


[230] Sib,—I have been «a interested reader of onr valuable Mechanic daring the last twelve months, and as this is tho first time I have addressed yon, I cannot bnt congratulate yon on having such as. array of talented contributors on an almost endless variety of subjects. Truly there is a national education for the working man at twopence a week! II you think a few lines of mine worthy of admission into your columns, I would reply to an " Ambitions One " who is desirous of knowing how l»L.D.'s are made.

An LL.D., or indeed, any degree obtained in a British university, undoubtedly confers honourable distinction on its possessor, and I would add that a foreign degree is not inferior if obtained in a fair and legitimate way (i.f. not through mere money considerations).

For some years past, however, foreign universities, particularly German ones, have for a pecMiary consideration granted LL.D., Ph.D., and other degrees for sums varying from 4J15 to ±"25, and we frequently see a plain Mr. on one day emerge a full-blown Doctor on the next. I am personally acquainted with more than one who have thus obtained diplomas. It must surely be a standing disgrace atike to both university and candidate, when the latter obtains his diploma merely through purchase.

The subject of these Gemnn Yeast degrees has lately been fully exposed in the ticholastic Register. Tho number for July last, contains the following remarks:— "The University Degree Trade has not been thriving lately; a result that is mainly due to the exposures which have appeared in onr columns. Some of tho agents have entirely abandoned the occupation; but there are still two or three in the field. The facilities offered by these gentlemen are, however, now of a somewhat restricted character, as nearly every European university is closed to every person who is unable to pass a somewhat strict examination."

It the above remarks are true, and an "Ambitious One" is desirous of becoming a learned Doctor in so degrading a manner, he had better set about his business at once, ere he bo too lato. The authorities are apparently beginning to see that their degrees, otherwise valuable, are likoly to become valueless, since it is impossible to distinguish between those purcluued and those earned by laborious study. Steel Pen.


[231] Sm,—Your correspondent" W. S. A." (p. 469) appears to forget that we live in an age of railways and telegraphs, and the old fashioned stage coaches and their living prototypes have grown out of date.

As steam superseded manual labonr, so quick writing supersedes slow writing. The "true, correct, and beautiful form of the letters," as " W. S. A. " in a burst of poetic feeling expresses it, belonged to tho days of the "sleepy Charlies." In these modern days of "tarnation hurry," it is neither necessary nor desirable for business men to write as exquisitely and carefully as schoolmasters or professors of writing. It is not :tyle but rapidity that is aimed at this rapidity unavoidably results very often in illegibility.

"W. S. A." alludes to writing as an " art." Now to the great majority, who use it merely as a means of conveying their thoughts to others, it is not an art. Schoolmasters and a few others have made it an art for the purposo of teaching writing, but after quitting sehool it is not necessary for those who do not intend to earn their bread by forming their letters in a "true, correct and beautiful style" to write like schoolboys. There is no departure from truth, and therefore there can be no ignorance or vulgarity, in not forming tho •letters correctly. Modern excellence is to be able to write three letters in the time formerly occupied by one. Time flies and man walks. We should not c*nsnme time unnecessarily, lest time should consume us before we are aware of having wasted our allotment. Lex.

THE FRENCH MITRAILLEUSE. [282] Sir,—The Franco-Prussian War and the part being played therein by the mitrailleuse will probably cause brother readers te welcome theannexed illustration • and description of this deadly weapon. The mitrailleuse is the patented invention of M. Francois Jules Mauceaux, of Paris, a gentleman well known for his various improvements in firearms in general, the English patent having been secured through Messrs. Robertson, Brooman, & Co., patent agents, Fleet-street. A mitrailleuse was patented by M. Manceaux in 1867; the present invention, however, is a great improvement upon the former weapon. The first part of the present improvement consists in fitting the barrels between plates which stretch across from one side to the other, and are connected to side plates or straps, which are carried on

[merged small][graphic]

trunnions. The trunnions enable the apparatus U> h monnted upon a carriage, so that it can be used in fcB operations.

The principle of the French mitrailleuse will be see from the accompanying engravings, fig. 1 of which is i sectional elevation of the weapon and carriage; fig. 1 is a section of the breech end; fig. 8 is a section of tfet breech end, with the block or closer drawn dorcr leaving the barrels free to be loaded -, and fig. 4 is. » sectional plan, with the cartridges in the barrels u« the closer screwed home. This compound gnn is composed of a series of barrels, which are fitted betwcea plates A A, which stretch across from one side to tie ■ other so as to firmly nnite the two side plates B B, open ■J which the trunnions are formed for supporting the mitrailleuse upon a carriage, so that it can be moved from place to place and employed in field operations. ——■^ The rear ends of the side plates B B are of greater thickness than the other portions, and are slotted so guide plates of the closer can work therein

that the

jjjj£^ These plates are centred upon pins, winch are kept*
'- r31 position withont working loose by means of tappets
acting upon the nuts on their ends". The breech-eloaer
plates O extend a distance beyond the rear end of the
barrels, and have near their ends long hides, which
serve to hold secure a transverse bar J. The central
portion of the transverse bar is of larger diameter, or is
thicker than the other parts, so that the threaded rod
L, which passes through it, may be turned so as to
bring the breech-closer nearer to or further from the
rear of the barrels. The front of the threaded rod L i^

[merged small][graphic]

rounded, tho rounded portion being fitted between two half plates q q.

TVie ander side of the closer plate bas lugs o v for carrying a pia V, to which the upper end of a link or lever bar V if jointed. The lower end of the link is pinned to a lever Q, so that the closer, when released from the barrds, can be raised and lowered upon their joint pins H H, which are fitted in the side plates B B. The under side of the rear of the side plates has projections for the closer to slide upon as it is being moved, and when it h&s travelled such a distance as to be tilted, it rests upon a plate h, which forms part of the closer frame G G. The front of the closer or breech block O has a face plate P secured thereto. This plateis provided with a series of holes corresponding to the number of barrels filled in the frames upon the carriage. The holes are threaded for the reception of screw pings or nipples, through which pins arc fitted. The inner ends of these pins rest upon a disc of horn or other yielding material, so that when the explosion takes place the force of the recoil is diminished. The distance the pins may project is regulated by a washer or ping screwed into the back of the plate P. Under the rear of the breeoh end of the barrels is attached one end of an elevating screw, by which the depression or elevation of the barrels is governed. The lower end of the Bcrew works in a block or socket on the carriage.

The drawing back of the breech-closer is regulated by a hand lever, and it can be retained at the required point by means of a pawl working in the teeth of a ratchet wheel fitted on the side of the frame. When the barrels are filled or loaded with cartridges, and the breech-closer brought in contact with the rear of the barrels by means of the lever handle, the fire can be communicated by means of a percussion cap, or fuze, or quickfire at one side of the barrel framing, which fire is instantly forced through a hole, and impinges against the cartridge case with sufficient impulse to break it and explode the powder therein. The explosion in the barrel causes fire to be driven through another hole, which leads from the first barrel to the second, and this causes the second charge to be fired in the same manner as the first, and from the second to the third barrel in succession until the whole of the barrels on that level have been discharged. The fire then passes up to a second series of barrels, placed above the lower series in succession, and in a similar manner to a third series of barrels.

Wrx. K. Hibdet.


[283] Sie,—T he annexed illustration of this celebrated weapon, showing M. Chassepot'a latest improvements, will probably interest the readers of our Mechanic.

In its original form failures occurred in practice with the rifle traceable to the form of cartridge used. It became, therefore, the object of If. Chassepot's later improvements to adapt the gun for the employment of flanged cartridges, and to provide the arm with an automatic arrangement for extracting the cartridge cases. Fig. 1 is a longitudinal section of a fire-arm constructed according to these improvements. Fig. 2 is a section showing the extractor in the act of withdrawing the cartridge case. Fig. 8 is a transverse section through the line 1, 2 of Fig. 2. Figs. 4, 5, and 6 are separate views of the extractor. The movable head shown in the engravings of the first gun is dispensed with, and the caoutchouc obturator is replaced by a metallic piston a. Through the centre of this piston a channel of truncated conical form is formed by the passage of the striker or needle R (which it shortened), when impelled by the spring T. The metallic piston a is lodged in a chamber in the front end of the breech-bolt B, and is hold by a screw <> passing through the side of the bolt and entering a circular groove c on the outside of the piston. A square tooth or projection d is formed on the periphery of the piston near its head. This tooth serves to operate the extractor. The rear or tail/of the extractor ia in the form of a flat ruler terminated at the front by the extractor proper g, which is a curved piece having tho form of a portion of the inner circumference of the barrel, and having a recess to receive the flange o of the cartridge. The cartridge is shown in two positions; in Fig. 1 it is seen in the charge chamber, and in Fig. 2 as withdrawn from this chamber. A longitudinal groove or slot i is formed in the rear flat portion of the extractor, into which the tooth d of the piston takes. The extractor slides in a recess k in the bottom of the breech chamber.

The employment of flanged cartridges modifies the form of the charge chamber, and dispenses with the combustion chamber in the old rifle. The rear of the charge chamber, that is, the rear end of the barrel, has a circular groove rfU to receive the flange o of the cartridge. A cavity a1 is formed to receive the ex


tractor proper g, which completes the annular portion at the entrance of the charge ahamber. In withdrawing the breech-bolt, the tooth if of the piston a, reaching tho end of the groove i of the extractor, draws back the extractor, and with it the cartridge cose, which is then thrown out. When a fresh cartridge is inserted its flange enters the reeess oi of the extractor, which pushes it into place when the bolt is pushed forward. Thus, the extractor is operated by the bolt both to push the cartridge into place and to extract the case from the barrel.

The screw (which formerly passed through the main or top piece to enter the slotsfin the bolt) is now replaced by a plate p (Figs. 1 and 2), passed through this main piece and heli by a pin r; this piece serves as a tenon to slide in the groove of the bolt B. The tenon on the spring carrying rod f* is dispensed with, as well as the corresponding mortise in the button at the hind part of the bolt. The whole is replaced by a button or stopper L screwed into the rear end of the bolt. The sight rises on a Mnge towards the front of a barrel to facilitate operating it.

F. G. R., late H.M.R.A.


[2341 Sie,—It seems to me I might speak of the philosophy of subscribing to, and reading carefully such a publication as the English Mechanic. There may be a valuable principle involved: something that reacts on one's own whole temperament. To read and study such a paper will have the same effect on the mind as a good broom in a housemaid's hands upon the cobwebs. The whirr of science clears the crannies and calls thought into action. The perusal of such bustling pages is most suggestive. How can one be idle, lazy, or inactive? Owe must set to work at something. Just as when I go to church, I fancy I get more good by the trains of my own thoughts aroused than by anything actually said in the sermon (though the trains would not have arisen elsewhere); so also a clever scientific paper sets its readers a-thinking, a-thinkiug, and not only u-thinkin^, but also a-doing. Say that I read an

article on astronomy, or perhaps on making one's own telescopes. Very well, then there are those bookshelves. Just so. But what have bookshelves to do with telescopes? Not much, in one way. But think of the philosophy of the thing I The bookshelves ought to have been done "yesterday," and were to have been put off to " to-morrow." But now—Now'* the ticket. Thanks. to the telescope article, now, however hot it may be, off goes the coat, the shirt-sleeves are tucked up artistically above the elbow, out come saws, planes, hammer, noils, screws, sand-paper, and everything, and the overdue job is done; and it is the telescope artist who has done it, or set it a-going; and who knows but on top of the shelves, when varnished, will be a telescope, as a tripod symbol of success? Thus, in like manner, if yon tell a man how to make his own gas, or to construct his own barometer, he may do one or the other, or neither; but in any case you havo given him an impulse of energy, a push of progress, quite as accelerating and much more pleasant than a whack over the back with a stick, and a shout of " Go on, stupid ! '• The man must address himself to something useful; there is a ring or rattle of machinery in his ears, a gurgle of cogs and tfrwm* and bands (of genial industry, not of horrid war). The like is good, whether as work or as play, whether as bearing on livelihood, or as mere hobby and holiday, and every man ought to have bis pastime, and be choice about it, because if he has not a good one, he will have a bad one. Even ns amusement, mechanical occupation is beneficial, to body and to mind, to health and to comfort. I even imagine it promotes morality, sobriety, and so forth; at least it ought to do so, and might do so. For example, suppose I have to do with a goodly steamengine. There it is, the Titanic motor, with bones of iron and marrow of steam. I don't neglect it; and why should I neglect myself? Its polished parts are shining, its brass parts are brilliant; there is no rust on it; and why should there be any onmc? I can at least be clean. And, mind you, it is not necessary for tho hardest-working stoker or poker to be dirty: grease will get off tar; oil will wash off oil or paint; wash your hands in a spoonful of turpentine; a jug of hot water is easily got: get a wife to get it for you: go in for a lump of soap, and a pinch of Boda, nailbrush even, and bath ; make the bath yourself, at the worst. At any rate, be clean and tidy, like your steam-engine. Nor do you abu&o it or misapply it; it has its oil, its proper amount of drink; and, strange to Ray, that drink is water. Would water do for mo? Suppose I try? I never heard of a steam-engine getting drunk, unless the man in charge of it did, or went mad, like the Yankee regatta of two rival steamers among the suaga, where the captain sits on the safety valve, and .siugs out,'* Go ahead!" No, my model steam-engine in very sobering; it would get grimy if I let it, but I don't; nor will I treat myself worse. I'll be clean, neat, hard-working, clean again, hard-working again, .always sol*r, never muddled or puddled, always measured, aye, and merry too; as jolly old Juvenal saith, with a sound mind in a sound body. So I beg to enounce that the philosophy of the English MeChanic is the spirit of utility; it sets yon on to be serviceable to yourself and to others; not only in •^reai public '" patents " and improvement)*, bat aJao in natty tidy home contrivances. And all the while the whole thing in its very essence is a witness for selfrenpect, for decency, for personal cleanliness, for sahoaty, lor home happiness, and all that makes life worth living for. Glmkl.


[235] Sir,—As a constant reader of the EnglishMechanic, I have boen interested, almost amused, at the amount of disturbance cerebral, literary, and philosophical, which seems to have grown up out of a very simple question, put honestly and singly with a view of attaining information upon a subject of mechanical forces.

That an " F.R.A.S." should havo descended into Bo humble an arena was more than I had presumed to think of. But now whatever may be the tenuity of my own cerevisia, or of Messrs. A, B, or C (a point I ■nm not anxious to settle), ths thing I do wish to have understood, and which I probably failed to put with sufficient clearness before, is this:—Suppose a piece of ordnance at any point on the equator, and fired pointblank (or with such elevation as to give the longest range) first to the east, then to the west, in each case with the same charge, will any and what difference be found in tho distances to which the shot will have been propelled in this one case or in tho other, either from the atmospheric resistance arising from the earth's rotation on its axis, or from any other cause.

As the earth in its orbital motion carries its own atmosphere with it, it M presumed no difference would .ariae fraxn that source. It. T. Gould.

1236] Sia,—In reference to No. 86, p. 378, I would ioel grateful to Mr. Proctor if he would favour your readers with his view of this question, taking into account the small quantity D E in bin pap w on theearth's moti-n,p. 37'2, col. 3, of No. 249, 31st Dec, 1869. I observe that when tho question is confined to due east and west, as is done by Mr. Gould, and no elevation .stated, and if we take the elevation to be =0, then D E = 0 ; but the ball must in its easterly motion be retarded by the trade wind, whereas in its westerly motion it must bo accelerated by the same cause. I do not suppose, however, that this cause of disturbance is intended by the proposer to be taken into account, and therefore tho difference between the east and west motions will = U, as stated by "F.R.A.S.," p. 395. "When the ball is thrown vertically, a condition introduced by Mr. Usborne, No. 14S, p. 450, then D E loonies a maximum; and if the height be considerable, say 3,970 miles = earth's radius, the ball would require 2,075 seconds to ascend, and the same time to descend, which would give for D E a very considerable magnitude. M. L.


[237] Sir,—Not the least of tho numerous and important contrivances made by Providence for the comfort of his creatures is the twilight or crepusculum, by which we are gradually introduced into the rays of the nioniing'ttuii, and as gradually transferred from the reign of one mighty potentate to the dominion of his great rival night. Twilight commences with the setting of the sun, and lasts (so astronomers say) until the sun gets 18 below the horizon, when tho atmosphere ceases to reflect his rays, and it commences again with the early dawn, when the sun comes again within 18 of his rising point. Since twilight begins at this distance below the I horizon, we can from hence calculate at what height the atmosphere has the capability of reflecting tie sun's rays. It* actual height we are unable to ascertain, because, being an elastic fluid, it expands with considerable distention the higher it roaches from tho earth, and becomes of^such rarity that, as far as we know, it exerts no influence upon the appearance of the sun. If it were of the same density throughout, its height could be ascertained with great accuracy from the weight with which it presses upon everything around us; but this is not the case, as every aeronaut has experienced, and as others may learn from their descripUon. The causes of twilight are usually ascribed to the refractive and reflective powers of the atmosphere. By moans of refraction we have twilight sooner than we otherwise should; and by reflection it is diffused over all the expanse of the atmosphere. Refraction acts with much greater power in a dense atmosphere than in one of much tenuity, and is more considerable near the horizon than at great altitudes, gradually decreasing until the zenith is reached, when 2jo refraction takes place. By refraction, a ray of light

proceeding from any celestial object is bent, and in consequence, that object appears to our view sooner than it otherwise would. From the same cause, the sun and the stars have a greater altitude apparently than the reality. As a proof of this it is recordod that some Hollanders who wintered in Nova Zembla, some time ago, saw the sun 17 days sooner than they expected, which would not have been tho case had not the refractive power of the atmosphere raised that object {particularly as being near the noruon) to a greater altitude than computation made it. It is an admitted fact, then, that refraction makes a celestial object appear higher than it actually is. Thus, in figure let S represent the suu[; when, then, the ray S A strikes the atmosphere, it is refracted, and as it is unequally refracted by tho atmosphere, the refraction being greater in the lower and denser parts than in the upper, the line A M will assume a curved shape, and become, I suppose, what astronomers call the crepuscular carve, and the object S will be seen by a


man at M. If, however, instead of being the ray itself, it were a reflected ray, refraction would of course act upon this ray, too, which would have its share in illuminating the atmosphere. Suppose then an innumerable number of refleetedprays were in existence; all of them would be affected by refraction, and hence would throw their light, though in a diminished degree, upon the earth; for if refraction takes place upon every celestial object, it must also act upon the rays surrounding that object, and the consequence of this will be that, although wejslmll not be able to see the sun or heavenly body itself, we shall see the harbinger of that body's appearance in the dawn of the early morn. Refraction, therefore, has its share in the composition of the twilight, and it co-operates with reflection in gradually intensifying the dawn until it breaks forth into the perfect day. When reflection acts upon the ray S A, it will throw the ray in an exactly opposite direction, and the angle SAC being the angle of incidence, will be equal to the angle C A M, or the angle of reflection; and hence we shall be able to compute tne height of the atmosphere. This, however, will be one ray only; bnt when millions upon millions of reflected rays pervade the snperineumbent atmosphere, light is diffused all around, and aipmals and men are roused to their occupations, and nature displays her attire to the gaze of all. Suppose, then, that when the son is 18° below the horizon the twilight begins, then tho angle M A S is equal to 162°, the supplement of 18°; and since the angle of incidence is equal to the angle of reflection, therefore S A C = CAM, or 81°; then having two angles and a side, we can find the hypothenuse A C, which is equal to 4,031 miles, from which subtract C E, the earth's radius, and we have E A the height of the atmosphere, or 19 miles. And we not only can find the height of the atmosphere by knowing that the sun begins to illumine it at 18° below the horizon, but we can ascertain how long the twilight will last at any particular place. If, for tho sake of illustration, we take London on June 21, and wish to know the time twilight will continue, we must elevate the globe for the sun's declination— namely, 23£'\ and having made a mark upon London with prepared chalk, we shall find that it will only descend 15° below the horizon, and the consequence is that there is twilight at that time all night, and the twilight all night will continue until London, in the revolution of the earth round the sun, and in the rotation of the earth upon her axis, reaches 18° below the horizon, or until the declination of the sun is again 20J\ which wiU not happen until July 20. We infer, then, that twilight lasts all night from May 23, when the sun's declination is 20J°, and whilst he is travelling to his greatest declination'and back again to 20 J ^ which makes 58 days. And if we wish t.» find the duration of astronomical twilight at any place on tho globe, we must elevate for the sun's declination, and notice how long the given place will be before it reaches 18 below the horizon. T. S. H.


[238] Sir,—Tho weather during the lunations of June and July, 1870, has been very unfavourable for prosecuting the interesting series of observations on these objects which were commenced in April, 1869. While as many as 242 observations in 37 series were recorded in April and May, 1870, Juno and July have afforded only 80 in 18 series. The observers in April and May were Messrs. Elger, Prato, Gledhill, Neison, and Whitley; in June and July, Messrs. Gledhill, Elger, Neison, and Ingall. The observations in April and May gave a little undor seven as the average number of spots seen on any one evening; those in Jnne and

July a little above four. There can be no doabtStiii deteriorated state of our atmosphere has. contekx mainly to produce this result; tind if we take the Ee^ ber of separate observations as an approximate ensure of this deterioration, the good state is to lie >m as 3 to 1, nearly. It inu»t, however, be borne is ^•■•t that the number of observers in April and H*j \^ greater than in June and J«dy, and this psay fcgi^. m ast be modified accordingly. If w» enqoir** spots observed (IS) barf been affected doriag "Vunfavourable lunations, the following table, raaajeav-i the degrees of visibility for the two wete of tious uach, with the differences, also the the two corresponding sets in 180U, may tend toeav; date the question:—


The variations of visibility have been, u «i former occasions, irregular; and this irregularx' \ apparent on comparing the differences of 1670 rz those of 1809. It is true that in some cases the Cop of the annual curve is reversed, as shown in 5i* 14, aud 16, and this is to be expected with a dtten*rated atmosphere; still the greater decrease of liability of spots Nos. 4 and 14 is irreconcilable upon tag view with the increase of visibility of No. SO, Dawts'i companion of No. 3, a small erateriet reqaina; generally a line state of our atmosphere to see it. No. 3 has also increased in visibility during the la?t two lunations. Of the spots which were sufficiently observed during the first year to afford curve? of visibility, the following were n.*t seen (hiring the two lunutions of Juno and July—Ttje., No*. 2, o", 7. 10r 13, 19, and 22; of those which ar* common w the first year, and the two lunations Jsne and July of the second, Nos. 3 and 17 maintain a high degree of visibility, while Nos. 4, 14,16, and 5 have fanen considerably. Tho only spots which have exhabited a nigh degree of vesibility under all states ol our|pvrn atmosphere are Nos. 1 and 17, and thete, with the increase of such a small spot as No. 30, lead to more than a suspicion that the variations of visibility at all seasons are in a great measure independent of variations o! our own atmosphere.

Mr. Elger has pointed out that the markings aa<j spots are so closely connected as to be regarded « cognate phenomena. The greatest number of *jw© observed on any evening was 8 by Mr. Elger os Jaff10, and by Mr. Ingall on July 14. Nos. 14 and 16 ■st seen by both observers on both occasion*, sad ale rarely visible spots, Nos. 12 and 31, were s**r fev Ui. Ingall on July 14. At tho same tinio he aitfiKd tfc* markings, and describes them aa appearing *itii »t lea&t ordinary distinctness. He adds, "Tt-iwtwAfcot the floor at times of fine definition, was corral witia spots of light.'' This is very remarkable, ash* apy^ar4 to havo failed in picking up some of those Fpotswaai were frequently visible in 1800, as Nos. 22, 13, aadW. aud is strikingly in contract with those stones ol 4? floor described as "very dark." Can it be that aa. such occasions there is a superficial covering of «s&* kind interfering with the ordinary reflection from tk« floor? or are the white spots themselves smaller superficial masses reflecting a greater quantity of right*

I will forward another extract bearing npon brightness and colour in a few days.

W. R. Bin-r.


[239] Sib,—When Debain, of Paris, first invent* the harmonium (or, one might more correctly Bar, tir* brought into the notice of civilized Europe an inveotua long previously known to the Chinese under a ruder form), all those of us who happen to be musical a* wed; as mechanical, went into ecstasies about the new instrument. It had long been a want to provide some keyed instrument for private use, cheaper and leas eunibrouthan the organ, which would give us sustained tones capable of interpreting organ music. And we thought we had found it. At llrst the novelty made ns blind (deaf rather) to its important defects. Bnt gradually j one came to discover that the very best harmonium* have necessarily, from their construction, these very sad defects—1, the tme is of tho reed, utterly and irretrievably reedy; 'J. the bass overpowers the treble; 3, the intonation is Ho sluggish that it is only adapted for the slowest of music. And even when Kauimann, of Dresden, introduced tho percussion action to rem«dy this last defect, although a palliative, it was by no mean a cure.

For these reasons I, for my part, and I am sure I may say the same for all my musical friends, had long given over the harmonium as a musical instrument, and relegated it to the country chapel and the schoolroom as an accompaniment for hymn tunes—bett*r, certainly, than the discordant flute, and fiddle, and clarionet, which it very often displaced—but still, very bad, both from the impossibility of distinguishing th e air aud the impurity of the tone which causes it t# oat th rough the voices and drown them with its buzz instead of supporting them.

And iu enumerating these defects I do not refer to bad harmoniums, but to the best. The faults are as inherent to a 36* atop Debain, or a 2-1 stop Alexandre, or ^s of Schicdmayer's best instruments (and I have tried in-) lib to u common six-guinea harmonium. t 'utirely given up reeds for musical purposes, TJH^ d out. Last March I wrote Me&srB. Brwwington & Son J, for a Mason &. Hamlin organ No. 40, an 8 stop cabinet withvoxhumanu and two rows of keys. I had grave doubts about it at the time. I confess I read Messrs. Mason & Hamlin's certainly very glowing prospectus of their organs with some suspicion, knowing that folks iu New York are not incapable of very tall talk. In due course my organ arrived, and I am not sure 1 can give much greater praise than by saying that every word of the prospectus X found literally and scrupulously true. It i* the ideal of what musicians have longed for in a harmonium. The tone is round and pure, as different to the reediness of the best harmonium as can be. It is resonant, the chords ringing again through the hollow-chambered case after they are struck. Thobass does not overpower the treble, but by a particular system of voicing the reeds, every note in the register is of equal power. The intouation is so perfect that the touch is as rapid and delicate as a pianoforte, without any trick of percussion action. It is consequently adapted for any style of music, from the lightest dance morceaux to the heaviest mass music. Best of all, so pure and true is the tone that even used at full power with four sets of reeds, it will not drown a solo voice.

Now the great difference in principle of construction between the Mason & Hamlin organ and the harmonium is so simple that it is strange it should not have occurred to English builder?. Take a violin string and stretch it on a bit of board, and try with a bow to get tone out of it, and we might liavo come to the conclusion that there was no tone to bo got from a string, did we not know that by stretching it over a hollow case instead an Amati violin is made. Messrs. Mason & Hamlin do the same tiling with reeds. Each reed is placed in a separate chamber over a delicately resonant sounding box, and the result is perfect organ tone. I would not be misunderstood in using this expression. I employ it in exactly the same way as we say an 8ft. stopped pedal pipe gives a llift. tone. The tone is the same though the volume and the depth are wanting. Just so closely does the American free-reed organ approach the pipe organ in tone. As the builders very honestly say, " If you can afford £300 to buy a pipeorgan get one in preference to one of ours, but if you cannot, we can supply you for one-third of the cost an instrument of better tone and capacity than any cheaper pipe-organ." This is undeniably true, as I can bear ready and willing testimony. And as regards oven the cheapest American organs with one set of reeds, the tone is as pure, although, of course, the capacity for variety, afforded by a greater number of stops, is wanting.

Amongst other differences in construction is the employment of very powerful exhaust bellows, whereby the air is drawn through the reeds instead of being blown into them. Anyone who has used a "mouth harmonicon" must have observed how much better tone id obtained from it by drawing in the breath than by blowing through it. The reeds are moreover heavier in make, and the tongues of a different pattern to those of the harmonium.

The vox humana is an ingeniously simple piece of mechanism, which produces a delicate effect for solo playing, only comparable to the articulation of the voice, or the vibration of a violin string beneath the bow. So far from being a monotonous and vulgar effect, like the wretched "hubble-bubble" of the old tremolo stop, it is so dainty as only to be noticed when one listens for it. It is contrived simply by a rotating fan at the top of the instrument, which vibrates the air after it has left the reeds, instead of before. The automatic swell is the most perfect I have ever seen, enabling a performer to command the power of the instrument from a whisper, soft and crisp as a musical box, to its full capacity, without any difficulty such as is experienced in "keeping the wind in" when playing on a harmonium with the "expression" stop out.

No one who has ever tried an American organ will think of going back to a harmonium—indeed, when one of them is placed side by side with a much more expensive harmonium the difference is so painful to any one with a musical ear, that the buzz and reediness of the harmonium is simply intolerable.



[SKO] Sib,—The cross westward of Foutenelle, figured by "Foreigner," appears to be nearer to the crater than that mentioned by Boor and Midler, and in the position of their delta. If I interpret the general figure of "Foreigner" rightly, the mountain range S.W. of Foutenelle, not shown by B. and M., but very plain on Rutherford's photograin of March 6, I8t>5, would lie parallel with the S.W. side of B. and M.'s lozenge, which side, according to them, is a broad light streak not shown by "Foreigner." It is the JCW. side of the lozenge which contains B. and M.'s crosB in the position of thoir seta, some distance "\V. of "Foreigner's" cross. These crosses I havo no doubt are formed by intersecting fissures in the mountain ranges. There are two intersecting fissures of the same kind in n depression north of Pletto, which may be seen under a suitable illumination, with n comparatively small aperture. It would be well to btndy these features in connection with surrounding

objects, as they evidently point to fteismotic or earthquake action. By the way, this will introduce a few remarks on the letter of "Littus Habet Conchas," who alludes to a continued series of critical observations of the moon's surface as not tending to establish any corresponding physical resemblance between tho earth and moon. May I be allowed to ask your correspondent if he will kindly inform me in what work I can meet with such a series of observation*? The latest series of seleno-topographical notices that I am acquainted with is by the Rev. T. W. Webb, published in the Intellectual Observer' This series includes numerous very valuable observations of his own, but they hardly possess the character of a continued critical series which can be used in finally disposing of the question as to the similarity of the moon and earth, or the opposite, although there are many observations that bear upon it.

For myself, I may say that after eleven years of close observation of the moon, with telescopes varying from '2*75 to lOin. aperture, my own impression is that the moon is more earth-like than it is generally imagined to be. If the reader will kindly turn to page 43t! of tho English Mechanic, for July 29, he will find mention made <*t a lino of cliffs, part of which form tho S.W. border of Hipparchus. These cliffs I have most attentively studied, and I know of none of the features of the moon, and they are numerous, which are more earthlike in appearance. The line of cliffs is exceedingly analogous to a terrestrial coast-line. Whether the "fluid masses," occupying the interior of the "hollow spheres" of your correspondent, sufficed to produce the appearance of erosion on the faces of the cliffs towards Kipparchus is a question that may or may not be settled by future observations; at all events, all the "hollow spheres" N.E. of the cliffs could hardly have ejected sufficient "fluid material" to have affected them, and it is difficult to understand how tho "fluid masses," once occupying the interiors of KaXley and Hind, could havo eroded the cliffs below them. Let us look at this matter for a few moments in the light that a most careful examination of the whole region will afford. Referring to the article already quoted, south of Halle y and Hind will be found a tract of high land, certainly the highest in this part of the moon, and probably the earliest formation hereabout. This high land appears to have been dislocated by a "fault" which is traced to Tycho, on one of tho lines of the last distribution* and settlement* of tit* typical lava of the bunt sliell* of the spheres. Of the precise nature of the surface at the time when tho dislocation took place we are ignorant, especially as to whether the "hollow sphere" Kiiul was then included in tho mass of high land, and it is difficult to obtain a true ideal section, but we have good evidence to show that the dislocation took place before the bursting of the "shell," for iu its neighbourhood the "fault" is certainly interfered with by tho grooves, which are apparent on the sides of the "crater" Kind. After this the evidence is strongly conclusive, either that the cliffs before referred to were raised, or that the surface N.E. of them subsided, for they cut off abruptly the slopes from the "crater " Kind.' And here we may institute a comparison between the apparently more ancient craters Hind and Kaltey (premising that the "hollow sphere" Kalley burst after the cliffs were formed), and the more recent one Aristillu* on the Palu* Putredini*. The result of such a comparison I leave with the intelligent observer, who is acquainted with the agencies producing and affecting our geological phenomena. Bo not theso successions point to such slowly operating agencies as we are familiar with in the earth's crust, and cannot we find terrestrial analogues to lunar craters, such as Kind and HalUy, on the earth's surface? for example, Sanlorin, and such as those partty filled and broken craters ou the bordors of the Maria, on our sea c*ast— Torbay, for instance. May not Bo close a scrutiny as the lunar Hipparchus has undergone, when extended to the whole moon, contribute to the detection of an increasing number of terrestrial an alogucs?

In conclusion, I would just remind the reader that the article "Telescopic Work, &c," on page 418, contains a description of the formation adjoining that sketched by "Foreigner." W. R. Birt.


[2*1] Sir,—Mr. James Harrison has written a letter on tho subject of tho "Link Motion" in No. '275 (July 1st), in which he reiterates with amusing earnestness his erroneous opinions concerning1 it.

He says, if I (J. B.) "was well versed in link motion, I never would have said that the whole amount of vibration must be communicated to the centre of the link.'' I did not say anything of the sort, as any person can see by reading over my letter in No. 27a, June 17th. What I did say Ib this:—" That the amount of vibration that tho middle of the link should have is found by adding tho lap and lead of the valve together, and multiplying the sum by two, and it must have that amount, and impart it to tho valve-spindle too, or it is all wrong; " and I hope to be able to make Mr. Harrison understand the truth of that proposition, and the practical necessity of carrying it out in the steam engine, before I havo done with him.

In the Ktter alluded to, I gave an instance to illustrate this rule, in which the valve lias IJin. of lap, and Jin. of lead, which together make ljin., and multiplied by 2 give 3Uu. as the proper amount of vibration for the middle part of the link; but in that instance I said nothing at all about the throw of the excentricB or the full motion of the end of the tink, because I was then merely proving, in a rough way, the necessity for

motion at the centre, and giving tho rule for findii • its umount. The motion at the end of the link, or the "full amount of vibration," is another thing altogether, and is of course always much greater than the centre motion, but is never any particular measure of it, as the amount of end motion depends upon the greatest length of stroke the designer wishes to give the valve; and the centre motion is fixed, as I have just said, by being made equal to twice the sum of the lap and lead, or twice the "lineal advance" of the excentries, and this is what we might call the normal vibration of the link centre, which is increased by the crossing of the rod* in one arrangement of the gearing, i* decreased by the same cause in another arrangement, and is neither increased nor decreased by a third arrangement; but all this will be explained further on.

Mr. Harrison still "emphatically denies" the existence of any motion at the centre of the link "when that centre is in a line with the valve spindle and crank shaft, and the diametrical centres are in opposition to each other." He also says that, "both excentrics have the one throw" \righl), "and travel one distance" [right), "and at the same speed"" (ierong), "but in opposite directions" (wrong). The excentrics, and of course the ends of tho link, move for a considerable portion of each revolution in the same direction, and the reason of that is, the centres of the excentrics are never set in diametrical opposition to each other, as Mr. Harrison supposes, but in practice are always placed more or less on one side of tho diameter line.

A line connecting the centres of the two excentrics will not pass through the centre of the shaft, but is always some distance from it, and that distance is known amongst engineers as tho "linealadvance" of tho excentrics, and its amount is determined by the amount of the lap and lead of the valve. I have no doubt, from Mr. Harrison's writing, that this is the first time he has heard of the "lineal advance," for ii he kuew anything about it, or its objects or effects, he could not have perpetrated so many blunders in so small a space as he has done; but if he has patience and humility, and aptitude to loam, ho may acquire some knowledge of the subject before I have done with it.

But even if tho excentrics were set without any "lineal advance," and with their centres in "diametrical opposition," Mr. Harrison would bo no nearer right than over, for the ceutro of the link would still have some vibration due to the crossing of the excentric rods, as I explained and illustrated in my last letter; and tho exact amount of this vibration would depend upon the length of those rods, the length of the link itself, and the throw of the excentrics; and this centre vibration can never entirely disappear till Mr. Harrison, or some other person, makes a link motion in which the exceutric rods will have infinite length, the link itself no length at all, and in which the circle described by the centres of the excentrics shall be no larger in diameter than a mathematical point; or till he produces a link motion in which there shall be no crossing of the rods; and that, I may as well tell him, is quite practicable, and at the same time quite useless, for a motionless centred link u-ould not do for working a slidevalve at all.

I wiU now proceed to place before Mr. Harrison and "our readers" the link motion as it really is in practice, and I wiU explain and illustrate the principles of that very simple, beautiful, and imperfect contrivance in tho plainest language I can command, Bo that even Mr. Harrison, and other gentlemen like him, who have yet to learn the very ABC of the business, may be enabled to understand it.

Fig. 1 is intended to show the mechanical impossibility of constructing the ordinary link motion so that the centre of the link shall have no vibration. The centres of the excentrics are set in diametrical opposition or without lineal advance—that being the position in which. they impart the least motion possible to the centre of the link; and whatever the amount of centre motion in thi* case may be, it is caused entirely by the crossing of the excentric rods, which crossing is an unavoidable necessity of the case, therefore, motion—more or less—at tho centre of the link is unavoidable; but we always want a great deal more motion at tho centre than is. imposed upon it by the crossing of the rods, and tin* additional motion is got by placing the excentrics so that a line connecting their centres shall be at the required distance from tho centre of the shaft—and this is the lineal advance as explained above. In all these figures the excentrics themselves are omitted, tho centres only being retained as all that is necessary to the explanation.

In Fig. 1 there are eight different positions of the gearing shown for one revolution. This figure is drawn from an actual half-size model which I have had constructed especially for the purpose, and the amount of vibration at the ends and centre of the link is faithfully shown; the excentric rods are 3ft. long, the link is Itfin. from centre to centre of excentric rod ends, and the circle described by the centres of the excentrics is Hin. diameter, consequently the ends of the link have Bin. of vibration in all positions of the motion; the link is suspended by the centre, and tho length of the Buspending bar is 21in. The amount of motion at the centre of tho link is l£in. In my former letter I said it was 2in. for a similar valve-motion. I took that from *a inch scale drawing, hence the slight error; but l£in. i*? tho exact thing, and is what the model shows. C V is the main centre line of the crank shaft and valvcspindlo. The link is shown in "middle-gear "—as it is called—with its centre opposite the valve-spindle, or in the position in which Mr. Harrison " emphatically denies that the centre of the link vibrates," as if its position with regard to the valve-spindle could in any way affect its motion. How could it? The motion of

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