THE ORGAN BUILT.-IX.

[4714.]-IT will be better now to make the pedalboard, and although I intend to describe a radiating one, because I look upon it as the easiest to play upon, yet the same plan will do to lay out a straight one if preferred. Get twenty-five bars of pine, 11in. by fin. and 2ft. 2in. long, fifteen bars of American birch, lin. by fin. and lft. Gin. long, and ten pieces also of birch, 3in. by in. and 4in. long. Make an irregular-shaped frame, 2ft. bin. long on the front side and 8ft. long at the side next the organ (see Fig. 1), divide it out into twenty-nine equal spaces, and make a mark in the centre of each space, and then obliterate the sixth, fourteenth, twentieth, and twenty-eighth marks, counting from the bass side; by obliterating these marks a proper space will be left between the B and C, and also between the E and F notes. Next insert pins of iron wire in the marks. The size of the wire should be No. 12, and the front row of pins on which the pedals are centred should be 1fin. long, and driven in so as to stand 1in. high. The guide-pins should be Sin. long, and go in. into the top and bottom rails. Drive them tight into the bottom rail, which should be of oak, and let them fit loosely into the top rail, so that the rail may be lifted off when necessary. On one end of the pine bars glue a piece of in. birch, 2in. long, and the width of the bar-viz., fin.-and under each piece of birch bore a fin. hole through the pine, so that the top edge of the hole just touches the birch (see Fig. 2). In the centre of the birch cut a small mortice, gin. long and the exact width of the wire used for pins, and on the under side of the pedal bore a round hole that will just let the pin into it. After boring the hole very slightly, countersink it; if the mortices are nicely out and fit the wire well, it prevents the pedals twisting over. Bore a hole through the pedal for the guide-pin

to the rail with wire hoops or staples. The front rail down far enough to allow play to the levers. In each is merely a guide rail, and the grooves must be cut lever insert two loops of whipcord to hook the trackers to. To insert them, bore a hole with a bradawl in the proper place, enlarge it on the under side with a taper bit, draw the whipcord through and drive in a small wedge dipped in glue in the enlarged side of the hole, then cut it off neat and close. By using whipcord a silent and at the same time a strong attachment is

secured.

J. D.

LUNAR OBJECTS FOR OBSERVATION,
SEPTEMBER, 1872.

[4715.]-SEPT. 5, Mare Crisium, direction and appearance of central ridges. Sept. 6, Azout, Alhazen. Sept. 7. Macrobius, Proclus, Mount Glaisher, the highest of the Coxwell range east of Proclus named by the late Dr. Lee to commemorate the highest balloon ascent. Sept. 8, Altai Mountains, Polybius, Beaumont. Sept. 9, Aliacensis, Reaumur, Werner. Sept. 10, Palus Nebularum, Palus Putredinis. Fine mountain scenery in the neighbourhood. See ENGLISH MECHANIC, Vol. XIII., No. 822, May 26, 1871, p. 222. Sept. 11, Sasserides, Pictet, Sassure. Sept. 12, Carlini, Lambert, ridges from La Place to Heraclides. Sept. 18, Riphean Mountains, Euclides. Sept. 14, Anaximander, Galileo, Lehmann. Sept. 15, Bettinus, Kircher, Wilson. Sept. 16, Zacbius, Hausen, Bailly. Sept. 17, Wilhelm Humboldt and Phillips just east of it, may probably be seen under the evening illumination.

The degree of luminosity of the bright spot in Werner is an important point to ascertain, and it would be well for an observer who has the requisite leisure to observe it regularly every lunation. It should be

B

compared with other bright spots in the neighbourhood, and its position in brightness should be placed on record, the names or designations of the spots compared being arranged in the order of brightness. The time of each comparison should be stated.

THE GYROSCOPE. because a writer has not full time for the complete [4717.]-I Do not agree with "E. H." (let. 4619) that (misprinted "proper") discussion of a subject he should let it alone altogether, for very often it may happen that a hint thrown out at a certain stage of a discussion may be of considerable use. As to what I threw out in this way I am certainly not prepared "either to admit that I have been in error or to put forward a convincing demonstration of its accuracy." But I am quite prepared to consider objections, if they are urged in a fair and courteous manner. So long as "E. H." refused to believe me when I pointed out that he had misunderstood me, it was hardly to be expected that I should care for the discussion; nor were matters improved when he said that he was prepared to see me "change my front" yet again. But in his last letter he avoids that objectionable tone.

In passing, let me remark that in saying that I am quite right" as to a certain fact, but that "no one has disputed the fact in the current discussion," "E. H." seems to imply that no fact may be mentioned until it has been disputed. I fail to see the force of this.

The subject of the gyroscope came naturally to be discussed in my papers on the "Earth, her Figure and Motions" (1 should have much preferred leaving it out altogether, but could not), and any one who will refer to my article (ENGLISH MECHANIC for January 21, 1870, pp. 445 and 446) will see how little I pretend to give a complete explanation. Moreover, I refer the reader to the true author of the general explanation there suggested. Nor was what I said a few weeks ago an attempt to explain the matter. Strictly speaking, I have made no attempt whatever to give a popular explanation of gyroscopic action; on the contrary, I have several times distinctly said that I believed no such explanation to be possible. Yet once more, I have not advised that "E. H.'s" explanation" should not be published." I advised him not to send it for publication, which is a very different matter.

Again, I have not said that I "have no doubt mathematical analysis would explain" the action of the gyroscope, but, absolutely, that mathematical analysis does explain that action-a very different matter.

"E. H." should be careful in making such statements, because a word or two introduced or omitted may quite alter the meaning. He has wasted space in making wrongly-worded statements, and has compelled me to waste more in correcting them.

As to the facts which "E. H." is supposed to be questioning, I do not wish to accuse "E. H." of quibbling; but what sort of answer am I to make to the remark that I ought not to have said "that the motion of one particle under the action of gravity would tend to shift the plane in one direction, and that of the opposite particle in precisely the opposite way;" since, Bays "E. H.," "the fact is that gravity tends to make both particles shift in precisely the same way-namely, in circular arcs having the point of support for their centre"? When I wrote the sentences (let. 4587, p. 460) which "E. H." supposes himself to be here fairly representing, it occurred to me that certain passages were so important as to require underlining. If "E. H." had seen the MS. instead of the printed matter I should have supposed he took the underlining for erasure. Does he suppose that when words are italicised they are meant to be overlooked altogether? Again, what he says about the particles moving in the same way is mere wording, not argument: in one sense, we may say that the particles of a grindstone in rapid motion are moving in the same way, though some are moving upwards and some downwards.

I maintain my original statement, not as a mere opinion, but as the statement of a fact, and one bearing importantly on the subject of rotating bodies, and tending to throw light on the apparent resistance which they oppose to the direct action of a force tending to change the position of the axis of rotation. If "E. H." chooses to imagine that in throwing out this hint I was pretending to offer a full popular explanation of the phenomena of gyration (and that in the very letter could be given) it is not my fault. With a gyroscope where I said I did not believe any such explanation

to work in; the hole should be gin. diameter, and lined with cloth to prevent noise. In the rail in front of the guide-pins cut a small groove for the end of the spring to work in. Having got the holes for the guide-pins finished, put all the bars in their places and mark the positions for the pieces of birch to be glued on (see Fig. 1), where the black lines show the birch, thus leaving the naturals higher than the sharps along the tread of the pedal, while the toe-piece on the sharps is sufficiently raised to clear the natural. On the ander side of the pedal mark the place for the end of the spring, and also mark the end of the bars, so as to cut them to an even length. Take the bars off the frame again and glue on the proper pieces of birch and fix in the spring, which is only a piece of No. 15 iron wire, and if the pedal-board is to be fixed to the organ, insert a piece of thick upper shoe-leather in the end of the pedal, as shown at A, Fig. 2; but if the pedal-board is to be loose so that it may be lifted up out of the way -for the benefit of the housemaid-do not insert the leather. I intend showing the action for a movable board: Before putting on the pedals again, fasten a thickness of felt or baize on the rail on which the pedals work, and two thicknesses on the rails where the guide-pins are-viz., two below the pedals and two above. If the baize is not thick enough, use three, or even four. Nothing is more disagreeable than to hear the movement clattering when playing, and a well-built organ may be as silent as a piano. Good carpet felt is sufficiently good for the pedal-board. The end of the pedal-frame is shown by the dotted lines Fig. 2. Now CENTRIFUGAL FORCE. make a rail, 8ft. long, of in. pine, and fasten [4716.]-LETTER 4646, p. 514 ("C. H. W. B.").-No mahogany rails to it (see B, Fig. 2, in which the front one in these days does maintain there is such a force. vertical rail and also the broad rail at the back are Writers sometimes use the term because it is well mahogany). Make twenty-five levers, 7in. long, and understood, and no other short term has been agreed cut grooves in the rails exactly opposite the end of upon. I proposed rectilinear tendency, and employed each pedal. The lever is fixed into the back rail by a it in a recent letter.

wire running through a bushed hole, and pinned down

M. PARIS.

RICHARD A. PROCTOR.

It seems to me that there is no place either for "depths" or shallows of "misapprehension" in such statements as these, and that if the moon in her falling towards the earth crushes "A.'s" philosophy, the flinging of the top, or the dropping of the pebble from the child's hand is equally fatal to Mr. Proctor's. My own glass-house being demolished, I may venture to retaliate on Mr. Proctor's little window, with the pebble he provides me with. I acknowledge the full force of his remark on "action and reaction" with thanks, which I also render to "L. H. O." for his experiments in weighing the top, which seem equally conclusive against both my theories. "L. H. O.'s" explanation does not, however, seem to meet the case. Perpendicular lines are wanted in his explanatory figure (4620), to show the [independent] action of gravitation on the particles at the ends of the diameter of the disc.

DEAR COAL-HOW IT MAY PROVE A BENEFIT. [4723.]-EVEN in warm weather the great price of coal is a misfortune to many, and an inconvenience to more; when winter comes on it will be to all who find it difficult to make both ends meet an addition to that difficulty. Unusual cost of fuel does more mischief, moreover, indirectly than directly, by enhancing the cost of numberless articles for the production of which coal must be consumed, more especially of such articles as iron, bricks, lime, &c. The evident causes of the rise in price of coal are increased cost of getting it and a temporary excess of demand above the supply, the consequence partly of increased consumption, partly diminished supply from shortened hours of pitmen's labour. Coal being an article which many cannot, and more will not, do without, the price may be very considerably raised in consequence of only a small deficiency in the usual supply, as appears to be the case at present, the increased cost of getting coal being considerably less than its increased price. This will doubtless produce its own remedy, for increased earnings will naturally induce other labourers to become coal-getters, until the cost of labour is reduced again to its natural level, unless that be successfully impeded by the operation of the anions of the miners; we must, however, expect, I think, a continuance for some considerable time of the high price of coal, and possibly, at least, a temporary rise.

position, and it exhibits no inclination to remove from tance. The top, though within the fall influence of that position when span, so long as no external force is that attraction, is not heavy enough, it is evidently inapplied, such as hanging a weight to one or other bear-ferred, to submit so obediently. "Its weight is in ing of the axis; in fact, the fly-wheel, whether spinning sufficient to change its direction in a brief interval." or not, is cut off from that attraction of the earth Yet, while the top's insufficient weight is to exempt it which makes a top fall instantly when you try to from the continual change to which the moon is subbalance it on its peg. If one of the bearings of the ject, the pebble dropped from the child's hand (and axis of the gyroscope were suddenly removed the in- which may well be less heavy than the top) is taken as strument would become a top to all intents and par- the example of obedient submission of matter to the poses, and I think any one will admit that it would be earth's attraction from which even the moon is not impossible for the instrument to continue spinning exempt. under such altered circumstances in the same manner as it did when it had two bearings to support it. Now to "Gy.'s" letter (4581). So far from the axis leaning more and more until the top falls over, it does precisely the contrary; in fact, the upright position is the one affording the least resistances to the top spinning, and the one which a top always assumes very quickly in whatever manner it may happen to have been spun at first, and it then, as the schoolboys call it, "sleeps." A good top-spinner can make a top spin at will, by a dexterous movement of the hand, after he has picked it up and has it spinning in the palm of hand, or in corner of thumb nail, or better in a tiny saucer, such as you buy gold paint in, with the axis inclining to right or left at pleasure, and on that dexterons movement ceasing the top gradually but quickly will stand spinning apright again. "L. H. O.," on p. 509, also seems to think that the axis of top will remain in one position, from what he says in line 28 et. seq. of his letter, which on the above showing is all wrong. He leaves the natation out of the question; but it must not be left ont, for as the axis of top, at first supposed to be inclined, does eventually come upright, and cannot possibly become so suddenly or in a straight line, the only possible line in which it can come up is a volute, or, what is the same thing, the nutation gradually decreases till it becomes nil. I leave "E. H." to practise and find out in what the "dexterous movement" mentioned above consists. There used to be a conjurer about the streets, whom I first saw in Hyde Park on the day after the Coronation of her Majesty, and who used to spin a large top in the air, catch it before it reached the ground, and then place the end (spherical) of its peg in a recess in the end of a long rattan cane, which moreover was considerably bent, and this he used to balance on his chin, and by moving up and down would make the top dance to the extent of two feet or more, and then would make it gradually deflect from the perpendicular till nearly horizontal, the little round knob on the end of the peg preventing it quitting its socket in the end of the cane, and then by holding quite still, allow it to resume the upright position. I may here remark that I never yet saw a London street boy spin a top decently (there being at least three ways of doing it). It may be from the fear of splitting tops on the hard stones and of breaking windows with the resulting fragments, that tops in London are universally, as far as I have seen, spun "anderhand" in one of two ways, instead of with the bold stroke from far above the right ear, right down to the left hip, that was in vogue at "our" school some 33'3 years ago. We also used fine whipcord instead of the thick string sold at toyshops for the use of top-spinners, and with great advantage as regards velocity of rotation. I am sorry to say in the last sentence of letter 4691, "A., Liverpool," appears to me to "maintain" rubbish, which he will probably not get "Sigma" to attempt to "controvert." J. K. P.

[4719.]-THE "curious contradictions" which were found by "E. H." in my letter (4510) are simply curiosities of misapprehension, traceable, perhaps, to some possible obscurity of the language in which I apologise for my own departure from "established ideas." I do not intend to charge "E. H." or others with doing so. I quite agree with "E. H." that the ideas embodied in the "ordinary theory 99 which I abandon, are not established by sound proof. I spoke of their establishment in men's minds by common acceptance. They crop up plentifully in one form or another, when the subject of the spinning-top is under discussion, and are found in Lardner's "Mechanical Philosophy." I think with "E. H." that Mr. Proctor's theory, so far as we can gain it by venturing to peep into the very little window which he has opened, is the same as "A.'s."

66

Another question, however, and perhaps an important one, grows out of the suggestion and experiments of weighing the top both at rest and when spinning at different angles of inclination to the earth. The whole weight of a top seems to rest on its point of support when spinning at an acute angle with the earth. This would be the position of a falling tree. In this latter case is the whole weight-that of the falling tree-exerted against the support at the base, until the position of absolute prostration is attained, or not? A top spinning on the scale of a balance at an angle (say) of 45 degrees, requires a weight equal to that of the whole top to balance it. If this is not so in the case of the falling tree, or other falling object, by what laws of force or matter is the whole weight of a top [spinning] in the same position transferred to the point of support? Every machine in which the wheel and axle receive rapid motion would be liable to be affected more or less by those laws which regulate the position of the spinning-top. Is this found to be so by the watchmaker and others? J. M. TAYLOR,

Seer Green Vicarage, near Beaconsfield.

[4720.]"E. H." says (let. 4690, p. 542) that the axis of a top or gyroscope would maintain the same inclination to the vertical were it not for friction and the resistance of the air. This, however, can only be true when the velocity of rotation is considerable, for if a very slow motion only is given to a top it will fall. There must be, therefore, some definite velocity of rotation, above which the inclination of the axis remains the same, and below which the inclination from the vertical increases, and the top or gyroscope ultimately falls down. Suppose we take a gyroscope, whose entire mass is contained in a ring 1ft. in diameter, and suppose that the distance of the centre of the ring from the point of support is also 1ft., and the inclination of the axis from the perpendicular is 30°. What would be the least velocity of rotation sufficient to keep it from falling, and how is this velocity to be calculated?

GY.

WATCH REPAIRING. [4721.]-"ABERDEEN WATCH JOBBER" (let. 4609, p. 489) states that I have not made it quite clear how to "bump" a Geneva escape-wheel so as to avoid "a smash." If he will refer to p. 421, probably his opinion may change; for at line 13, column 3, he will read that I foresaw the remark, and so dealt with the "bumping" process; then at line 15 I say in other words, "Don't." If this be insufficient, I will write again.

Concerning the bulging of pinion when it is a soft one, "Aberdeen Watch Jobber" is perfectly right so far; but then if the "jobber" should be so unfortunate as to strike the punch with "too much" force, the result will be as he states; but I never saw an escapewheel so much out of flat as to require so much riveting as would destroy the pinion, as he states. When they are so, in most cases they are originally left so by the makers, the escapement-maker having fitted the rivets too easy in the escape-wheel, and to tighten it had to rivet the pinion so as to bulge the pinion-head. Therefore my remarks concerning "low-priced" Swiss watches are borne out, in which I stated that the materials were left very soft in order to produce them quickly.

SECONDS' PRACTICAL WATCHMAKER.

In reply to Mr. Proctor, I beg to say that I am not eager to invalidate" established laws. I wish to see a new, because a more truthful, application of them to the subject. Without infringing on the rules of politeness, I may well inquire whether he has said anything in his letters to make one satisfied with old solutions? What the soundness of the theory may be which Mr. Proctor holds may be judged fairly from that "one feature" of it which he offers, and which must needs be treated as an essential part of it. I compare two sets of statements, which, in my poor judgment, directly contradict each other. "The moon " (let. 4509) " yields to the earth's attraction as obediently as a pebble drops from a child's hand," and this notwithstanding her TEETH OF WHEELS. distance from the earth, and the consequently [4722.]-THE gentleman who writes "Mechadiminished force of attraction. Her direction of nism" says, on p. 533, first column, half-way down, motion is continually being changed. Here is one set that the clearance between the teeth of wheels is someof statements. On the other side are these spoken times wrongly called "backlash." Of course, if it is of: "A top flung through the air;" "the top's weight no more than it should be, "clearance" is the word to has time to act, and eventually (the italics are mine) use; but may I ask what is the proper word when the "does so act as to change the direction of flight;" it clearance is excessive, or else varying in amount from is "insufficient to change the direction in a brief the teeth being badly formed? As I wrote on April 19, interval." The points of contradiction are surely p. 125, on the subject of "lantern pinions," and there conspicuous here. The moon's direction is being in third column used the word "backlash" in the latter continually changed, the top's direction only eventually. sense, I think it not improbable that the writer of The moon yields obediently to the earth's attraction, "Mechanism" had me in his mind when he found fault though that attraction is greatly diminished by dis- with the use of the word as above.

J. K. P.

It is an interesting question whether or not we shall learn the "ases of adversity," and turn our present enbarrassment to account, both by diminishing the cost of getting coal and preventing part of its excessive waste, both of which are easy to do if wisely set about, and if done even in a moderate degree would restore the balance between production and consumption, without putting any part of our population upon painfally short allowance. If, as is not improbable, the anions of pitmen attempt with any marked success to impede the reduction of their present unusually high wages by deterring other labourers from sharing in them, an impulse will probably be given to the introduction of coal-cutting machines by which the cost of coal-getting may be permanently reduced, and the tyrannical power of the unions effectually broken This will, I hope, be one of the lasting good results from the temporary evil; another will be, if many be now compelled to be more economical in the use of coal because it is unusually dear, to learn how to make less coal do the work of more, and if they do learn that nseful lesson effectually, a very large permanent saving will be the result of a comparative small temporary loss.

I have before shown that much more than half of the heat produced by the coal usually burnt for warming our houses is allowed uselessly to escape up the chimney, and that a large part of that which is not wasted in that manner is by using single instead of double-paned windows. Coal for mere warming is, however, burnt during part only of the year: doring the rest little is burnt in houses except for cooking, and the waste of fuel for cooking is generally greater even than that burnt for warming, besides being more constant and more general. If any one doubts this let him compare the quantity of fuel burnt in an English with that in a French or Belgian kitchen, or in other countries either I dare say, but I speak of those I have seen. I do not know the average quantity of coal burnt in English kitchens, it varies so very much, but I do know that in my own kitchen by the use of a halfopen stove instead of range, the cooking is better doue with a consumptionof about two-fifths of the coal formerly burnt, and that if I chose to look after it myself the consumption might be still largely reduced. I once used a closed stove (more economical, but less agreeable to use than a half-open one), in and on which two small joints and half a dozen smaller dishes could be cooked at once, with coke costing (at present prices) about three half. pence a day. It is impossible to save much out of so small a sum, but I have often doubted the expediency of lighting a fire at all when not desired for warmth, unless for cooking a large dinner. If I had time to spare I would try carefully the relative economy of coal and gas for cooking. I like best meat cooked in hot air or in steam, which is done very easily, either by using Captain Warren's cooking apparatus, or a common pan. The first consists of a smaller pan contained in a larger one with a double lid, when meat alone has to be cooked in it, or with a compartment above for vegetables, when they also have to be boiled in it. A little boiling water is put into the larger pan, which must be kept boiling, and the meat in the inner pan supported so that it is well out of the gravy. The steam surrounds the inner pan, and fills the compart ment above it, and the space of the double li. The meat is thus kept in air at the boiling temperature, and is gradually very nicely cooked. It is as tender as if boiled, and nearly as tasty as if roasted; sometimes wo

brown it before the fire to make it more like roast meat, which it then closely resembles, except being unusually tender. Now it is evident, if this cooking pan were covered with felt, and if escape of steam were nearly prevented, that the water in it might be kept hot with very little consumption of gas, indeed, I am not sure that it might not be kept hot enough without any additional heat at all, as in a Norwegian cooking-box. In either case it seems very probable that the cost of cooking would be trifling, and nearly all the fuel now burnt for cooking saved. A very simple saving is effected by letting the fire out as soon as the dinner is cooked, very little gas being needed for merely boiling a kettleful of water for tea, or for making coffee.

Gas, though a costly fuel in proportion to the heat it actually produces, is often a cheap one to use, because it need not be lighted before or burnt after it is wanted, while the quantity burnt may with care be

nicely adjusted. It would be very much cheaper than other fuel for many purposes, especially for cooking in summer, when heat for warming is not desired, if it were supplied at a price little higher than the cost of making it, as it easily might be with profit to the gas companies. Those companies are, of course, obliged to charge for gas consumed at night far more than the cost of making, often more than twice as much, because the cost of management, the interest and repairs of pipes, and of gasometers to hold gas made at day to be burnt at night must also be paid for, but for gas to be supplied in the daytime, and especially in summer, as gas for cooking would be almost exclusively, no extra cost for pipes or gasometers would be incurred, and any charge for it beyond the mere cost of making (and for a slight increase of leakage if more pressure were wanted) would be clear profit. It would be very easy for consumers who wished to burn gas at a reduced price for cooking, to have a second meter, and not difficult to prevent gas so supplied being used for illumination. The effect of such a change would be a more steady business for the companies, and a great convenience to the public. The winter consumption of gas would be but little increased, because when heat for warming as well as cooking is desired, coal or coke would be generally more convenient and economical, but in summer, when far less gas is used than in winter, and when consequently many of the retorts wanted in winter are standing idle, it would be easy without any increase of the works to make more gas than is at all likely to be burnt for cooking, even if the practice of cooking with gas became general. If it did, not only would there be a great dimination in the consumption of coal, but, what many would valne still more, in the production of smoke. The air of London might in summer be as clear as that of Paris, where wood and charcoal are so much burnt, our rain water might be fit to wash with. perhaps even to drink; we might grow flowers in our windows and courtyards, and the trees of onr parks and squares would not lose their leaves in early antumn. The consideration of other modes of saving fuel must be deferred for a future letter if you can spare room

for it.

COAL IN IRELAND.

PHILO.

GREATLY ELONGATED PROJECTILES FOR RIFLED GUNS. [4727.]-I SHOULD be sorry to oppose my opinion to that of "The Harmonions Blacksmith" (let. 4652, p. 515), but I must confess that I see one or two defects in his projectile, which I will point out. In the first place, the "ogival" form of head is considered the best, as it offers the least resistance in passing through the air. In the second place, although Mr. Whitworth employed shot which tapered towards the rear with advantage, it has been found that too great a length (with tapering rear) is attended with one great disadvantage-namely, the rear of the shot, being lighter than the forward part, is liable to be blown aside by a moderate wind, and the head turned to windward, In the next place, the point of the shot, besides not causing the gun to shoot to windward in a slight degree. being the best for flight, is a bad one for penetration. Whitworth's flat-headed shot were as good as any for penetration. The "Sabot" might answer as far it is itself concerned. Wooden bottoms have always been used for shells with smooth-bore guns, also for siege [4724.]-THE great advance in the price of coal is a matter which affects almost every one in a pecuniarys with both round shot and shell, and all brass field-guns. point of view. The supply of coals falls short of the demand, and any means of increasing the supply and lowering the price would be a benefit to the public. We lately exported coals to Belgium, now we import them, and the question is mooted if it would pay to bring coal from America. In Belfast we are now paying about 808. a ton for coals which used to cost 188. I observe, however, that some tons of very fair coal from Coalisland were sold a few days ago in Belfast for 128. a ton. This brings me to the subject of Irish coal. The coal-fields of Ireland, although much less extensive than those of England, are yet of considerable importance, especially at the present crisis. There is one in Leinster, two in Munster, three in Ulster, and one in Connaught. The coal formation of Leinster extends over large portions of the counties of Carlow, Kilkenny, and Queen's County. The Kilkenny coal is anthracite or stone coal; that of the other counties bituminous. The Leinster coal area is estimated in Griffiths' survey to be 5,000 acres, and to contain about 63 million tons

of coal.

In Tipperary there is a coal-field which may be regarded as a continuation of the Kilkenny coal; it is 20 miles long, and six broad at its widest part; a line of railway is being constructed between Clonmel and Thurles to connect the Great Southern with the Limerick and Waterford, which will open up communication with this coal-field. This coal costs 20s. per ton at the month of the pit, but the expense of carriage has hitherto prevented it coming into extensive use. The Munster coal-beds occupy parts of the counties of Limerick, Kerry, Clare, and Cork. Sir Robert Kane, in his work "The Industrial Resources of Ireland," says: They are the most extensive development of the coal strata in the British Empire." There are six layers of coal in this district, according to Griffiths' survey, but the beds are not thick; the coal is softer and more slaty than the Kilkenny coal, but is a kind of anthracite. In Ulster we have a coal-bed in the County Tyrone-viz., Coalisland; its area is about ten square miles. The thickness of the seam is 20ft. to 30ft.; it is situated about 600ft. below the surface; it is nsed now by the Newry Gas Company. The Connanght coal-field occupies considerable portions of Sligo, Leitrim, and Roscommon; it is about 200 square miles in extent. At the time of Griffiths' survey this ceal was sold at the pit's mouth for 4s. a ton! It thus appears that the coal-fields of Ireland are worthy of much greater attention than has hitherto been given to them, and are not unworthy of the consideration of the capitalist. PHILANTHROPIST.

We have some very long projectiles in the service for instance, the 7in. double-shell is 27-2in. long; it is cylindrical, with ogival head and flat base. Although found that a shorter one, with quicker spin, is in reality a very long projectile is theoretically the best, it is better: for, in a military arm, stability under all circumstances of wind and weather must be the object. Although the above are opinions of those in the service, I may say that the the generally-accepted best form of projectile is not yet finally settled. If "The Harmonious Blacksmith" could make any experiments with his new form of projectile, I should be very glad to hear the result, and if this letter be not quite satisfactory or not sufficiently comprehensive, I shall be happy to write again.

ARTILLERY CAPTAIN.

[4728.)-"THE HARMONIOUS BLACKSMITH's" bullet (let. 4652, p. 515) would be all very well if it could be fired without altering its shape. Suppose a "Sabot" could be made strong enough (which I donbt, unless made of some hard metal) to withstand the blow it receives from the charge, the bullet itself would be "set up," and instead of leaving the bore a fine tapering bullet, it would leave a crushed-up lump of lead, anything but fit for passing through the air. This "setting up" action takes place in all rifles where soft lead bullets are used; but, as they are only a very little smaller than the bore, and supported by it, they simply leave the muzzle a trifle shorter than when loaded. I am afraid that a mechanical-fitting soft lead bullet would be too much of a good thing; besides, it would be some trouble to place it properly in the grooves when loading. ARTILLERY GUNNER.

A TOUR ON THE CONTINENT. [4729.]-Ar the present time, when strikes and lockouts are unfortunately so general in this country, I have found it extremely interesting to travel on the Continent, and notice the difference which exists between German, French, and English workmen, as regards their hours of work and the manner in which such work is done. Travelling is as cheap, though not so rapid, as in this country, and with the aid of Cook's hotel coupons the expenses of living are quite as moderate as in England. With a knowledge of German and French, or indeed with French alone, it is possible to travel, of course, very much cheaper than we can do in this country, for to know the language is to have a double purse. With economy in the way of living, a great extent of ground can be got over, and much ECONOMY IN USING COAL. valuable information gained from a fortnight's tour [4725.]-COAL dust or slack may be readily burnt if through Germany, France, and Belgium; indeed, I mixed with clay (say three-fourths dust to one-fourth know of no route where £15 can be so profitably inclay; it throws out great heat, but takes some time to vested by an English mechanic anxious to obtain burn up. It would be extravagant to dry it before valuable information, and a pleasant change of scene putting on the fire, as it then burns out rapidly and does at the same time. not appear to me to throw out so much heat. It is best applied in the shape of large balls. The clay and dust must be well mixed.

At this present time I am burning "calm" (I believe the dust from stone coal), mixed with slime from the seashore, and so partial am I to it that could I obtain it when I leave here I would not burn any thing else. The cost is as follows:

Let me mention Antwerp, the first city I stopped at. I got up there on a Monday morning, and found the shops open at 6 a.m., the Cathedral open, and the usual morning services proceeding. The market is generally over by 8 a.m.; indeed, all travellers complain that they are always being disturbed by the ringing of the church bells, and the tinkling of horses' bells in the early hours of the morning, which is to be heard in

most continental cities. The working men seem to have an endless week of toil; frequently, have I noticed masons at work after 7 p.m., and Sunday only brings rest to those who can afford it; indeed, in Paris men generally work by the month, taking a day's holiday at the end, sometimes half a day in the middle. It is perfectly astonishing, and very sad, to see the uninterrupted manner in which work of all kinds is carried on day after day in the gayest capital of the world. It made a great impression on me this ceaseless toil, and the value of our English Sunday came to my mind as I had never experienced before. It must be necessary to man's health, to say the least, that he should have one day in seven as a day for rest from his daily work. In Germany, many kinds of work are carried on through the Sunday-harvest operations, for instance; almost all the corn is cut by hand, so that the hands have to be kept continually at work. Of course, there is a difference, and those who can afford, go to church or mass in the morning, and to the open-air Secular Concert in the evening, and appear to enjoy themselves; but, altogether, the value of a pause in the usual daily labour is very little appreciated on the Continent.

I was not in a position to visit any of the large factories at Cologne, or the Iron Works at Liège (the Birmingham of Belgium), consequently, I cannot speak technically of the actual hours of work in such establishments, but that the hours of labour are much longer than they are in England there can be no doubt, if we take the ordinary labouring mason as an example of the usual hours worked; while, as far as I have been able to form an opinion (after visiting Antwerp, Brussels, Cologne, Mayence, Strasburg, Metz, Sedan, Rheims, Paris, &c.), the men have a quiet contented look, and seem submissive to, if not contented with, their lot.

The custom of having the land let out in small lots, and the imperfect and awkward agricultural implements still used in Belgium, Germany (south), and some parts of France, appear to Englishmen certainly singular. was in a large field some 20 miles out of Paris on the The only reaping machine which I saw during my tour Northern Railway, and I naturally conclude that during unusually hot summer weather the corn must ripen too fast for the manual labour employed to cut it. Query, whether an English implement-maker would not make a good thing by sending some reaping machines over for the harvest time.

One word about the battle-fields. Those who expect to see marked traces of the bloody encounters which took place scarcely two years since will be greatly disappointed. Corn now waves and potatoes thrive on the black wooden crosses here and there mark the resting plains of Forbach and the fields of Gravelotte. Little places of the slain. At Saarbrück and Vionville, these crosses are massed together, and form cemeteries, near The heights of Spicheren, however, should certainly be to which monuments are now in course of erection. visited; and as the tourist climes the slippery side, studded with black cherry trees, he may well wonder how any general could have expected such a position to be taken except at a fearful sacrifice-it must have been complete butchery. One large mound I measured was 12 yards long by 5 wide; the base of the hill is dotted with numerous smaller graves, while monuments to commemorate the event now crown the summit. Bat I must conclude with the remark that the tourist should

visit Saarbrück and Metz; Strasburg, too, if he should go as far south as Baden-Baden, but not otherwise, as it is of little interest except for its really splendid Cathedral, from the spire of which a most capital view can be obtained of the Museum, Library, Prefecture, and other buildings destroyed during the siege.

The beautiful scenery of the Rhine, the gaming saloons of Wiesbaden, and the ruined Chateau at Heidelberg, should be duly visited, and will, no doubt, call forth the same feelings of admiration and surprise as I experienced myself. Take all money in English gold, which is the best coinage to carry anywhere on the Continent; don't trouble to get a Continental Bradshaw, as you can get any information respecting the departure of trains at your hotel, but, instead, procure a little book, entitled "The Rhine and its Battle-fields, and Paris," which the traveller will find most useful; the cost is only one shilling, and it is published by Simpkin and Marshall, London. I found it more generally convenient than the large guide book of Baedeker, which gives very full and minute accounts of all the principal places of interest.

In conclusion, permit me to wish your readers pleasant company and fine weather, both of which I was fortunate in obtaining during my late visit.

JOHN HUGHES.

Iry House, Hendon, London, August 7.

AN ECONOMIC CARRIAGE LAMP. [4780.]-I HAVE been experimenting on a method of producing a light for carriage lamps which may be worthy the consideration of some of our readers. A frictional electric machine is caused to revolve rapidly by means of a belt and pulley fixed on the nave of the carriage wheel; the stream of sparks collected by an isolated conductor are caused to pass between two small brass balls sufficiently separated, and fixed in the focus of the lamp reflector, where the candle or oil flame is generally placed. Of course, as the carriage moves the light is evolved, and the objection to it is its weakness or want of brilliancy.

A magnet might answer better, but this I have not tried. I submit the idea which, as far as I know, is original, to the readers, hoping amongst them some one will be found to add more light to this most economic lamp. E. B. FENNESSY.

MR. PROCTOR'S GULF STREAM MAP. [4781.] THE second sentence of Mr. J. Wilson's letter (4657, p. 587) shows the evil of an error I had intended to point out in the "equal-surface projection" chosen by Mr. Proctor for his twice-repeated map, pp. 478, 499. There was no kind of call or excuse for the distortion and excessive lengthening in latitude or compression in longitude, supposing the true ratios of surface the quality most needed. The preservation of equality in areas is consistent with any angular open ing that might be choser for the meridians in this projection; while an approach to correct forms was only possible by making the degrees on the mean parallel (or that of 40° for the particular extent of map Mr. Proctor had chosen) of their true length relatively to the longest on the scale of chords that divides each meridian, and this would have separated the meridians to about double the opening he has given them, those at the 80° intervals being inclined about 24°, whereas he has compressed them to little more than 12°. This at once alters immensely all the angles, and accounts for Mr. Wilson's remark on the false direction wherewith the current is made to impinge on the British Isles. Some error of this nature, however, would be inevitable in the upper and lower latitudes of any "equal-surface" projection, and leads to the very obvious conclusion, I think, that this kind of projections, instead of being fit, are extremely nnfit for this particular object, and indeed nearly the worst that could be chosen for it. They ought to supersede the absurdly deceptive Mercator chart indeed, for most of the purposes of popular maps; for distinguishing political divisions, for giving all the possessions of one power (as in Chambers's capital little map of the British Possessions), for natural history maps, of mineral, vegetable, animal or human distribution, density of population, relative extent of races, religions, languages, staple cultivations, &c. For all these, while Mercator's (by strange perversity the most commonly applied to them, is of all possible projections the most outrageously falsifying and misapplied)" equal-surface" projections are the sole right

ones.

It would be worth while to place side by side two pairs of figures I once made but cannot now lay hands on, one of Ceylon and Spitzbergen to an identical scale, the other as these two islands appear on Mercator; Ceylon being about six times the larger of them in reality, and Spitzbergen about six times the larger on nearly all maps made at present to include both. But for this particular purpose of Mr. Proctor's to show the forms of currents (or, indeed, any forms) I must contend that the proportionality of areas is a very minor advantage compared to identity of angles. Now to keep all angles on the map identical with those on the globe, we are not driven to the miserably misapplied"Mercator." There is another projection quite as easy, which keeps all angles identical with their true size, and yet with so slight variation of scale for surfaces that even if extended to include half the world (which it can easily do, and the hemisphere round any point we please) it only doubles the areas at the very border compared with those at the centre. This is the perspective projection from the antipodes of the map's centre (the earth being supposed transparent), the only perspective that makes all circles, whether meridians, parallels, or any other, project themselves by circular curves on the map, and therefore entirely to be drawn with compasses; even a simpler operation than the straight-lined Mercator frame. In applying this to the whole North Atlantic and 10° of the South, or all that Mr. Proctor had to represent, the very extremities, Wellington Channel, Guayaquil, and the Bight of Biafra, would have their surfaces barely a third larger scale (superficial measure) than the Azores or Sargasso Sea; a difference truly immaterial.

What Mr. Wilson says about absence of beaches on all the Atlantic coasts of Ireland and Scotland is very singular, if true, and I suppose will be soon contradicted if not so. But we must remember it is not usual for primary rocks to form any sea-beach, and these are precisely the parts of the British coasts that happen to be primary. Again, there are certainly shores and beaches to the North Cornwall and Devon coast opposed to the current as directly as any part of Ireland. The only secondary cliffs I know totally destitute of beach are those of Portland stone for the few miles between Durlstone Head and S. Adhelm's (miscalled Alban's) Head, Dorset, and these by no means meet any gulf stream, but turn towards the sheltered south-east, looking straight across to Cherbourg, which is said to be sometimes visible from them. So great a length of coast as half that of Ireland, without beach, would surely be a phenomenon almost unparalleled on the globe.

THE HARP.

E. L. G.

[4732.]—I HAD no intention of disparaging the harp in general, but merely that defective form of it which can be played in only one major key. This may have done well enough for King Brian and his contemporaries, but it can never hold its own in the nineteenth century against instruments of far greater capabilities. Almost all music that is worth anything, except quite plain simple airs, undergoes some sort of modulation, and then it cannot be played at all on such an instrument as the Irish harp. Transposition would, where accidentals occur, serve no purpose whatever. Would it not be better to sacrifice a few notes in compass and fit the harp with strings for sharps and flats? It might then be capable of becoming a really general favourite, as it is, it is simply nowhere.

VERTUMNUS.

IS THE MOON SPHERICAL? [4788.]-I DON'T know what Ch. Rabache (let. 4639) may be driving at, the moon may be a sphere or not, or green cheese. I'll never be able to go up to see, but I have read two most extraordinary things, which I would like some of our astronomical authorities to deny or confirm. I think it was some Italian savant who told this tale. Observing an eclipse of the sun, when totality took place, he suddenly saw a bright spot burst out in the centre of the moon, and believed this could only be caused by the disc of the sun being seen right through a hole in our satellite. This, I think, is the best example of "moonshine" I ever heard; but such a careful selenographer as Mr. W. R. Birt, I should imagine, could settle this. The second stunner was what may be Ch. Rabache's idea, that the moon was of shape shown in the sketch, with the shaded part turned to the earth. We know there are irrefragable evidences of the presence of water at one time; but my authority said the reverse side of the moon was a great valley into which the water flowed, and may, for all we know, be inhabited by a set of lunatics, and may have lakes, rivers, railways, steamboats, &c., but that the inhabitants never can see us or we them. Except some lunar Livingstone could crawl up to and look over the edge at us when he ought to see a big blue wall in space-blue on account of the colour of our atmosphere. I believe it has been stated that, with our present telescopic power, we could see a building as big as St. Paul's if it existed. Now, Mr. Birt, what do you say to all this? M. A. B. I call it unmitigated trash.

THE IGNITION POINT OF EXPLOSIVES. [4734.]—IN your number for July 26th I perceive an article on the above subject to which, as a patentee, I have devoted considerable attention for many years, and thinking the matter might be interesting to your readers, I send you a drawing and explanation of a very trustworthy apparatus I devised, which appeared in a London magazine some five or six years ago. I am induced to do so the more on account of the very high temperatures assigned to the various explosives given by the gentlemen named in that article, which so astonish me that I fear the metbod adopted was very faulty. Fibrous gan-cotton, for instance, is put down at 428° Fahr., whereas by my method, which is exceedingly delicate, it is only 320°. So ex uno disce omnes, such discrepancies being very serious.

D

REFERENCES.-A, retort-stand; B, gas-burner and regulator; C, tin oil-bath to hold thermometer and little porcelain igniting-cup; D, thermometer, ranging to 600° Fahr.

As the accompanying diagram states, I use olive oil as the caloric bath, which will absorb 600° of heat before it boils. Mercury would also do, but is objectionable on account of the fames, which may salivate a person. The manner of using the apparatus is as follows: Having placed the thermometer and little cap in the oil, proceed to heat the oil up to, say, 300° Fahr., the thermometer being graduated in degrees and half degrees, then let your assistant (for there must always be two persons engaged) project into the little cup as much of the explosive under examination as will lay on the point of a penknife. If it ignites instantly at that point, the temperature must be lowered, and a fresh trial made, and so on. Two or three trials at most will suffice to determine the precise point of ignition. This method has been so far verified that it is now in general use.

JOHN HORSLEY, F.C.S., Analytical Chemist. Cheltenham, Aug. 9.

ELECTRICAL SPARKS. [4785.]-I AM in receipt of Jane number; seeing that the sparks are still flying, permit me to confirm the statement of "Philo's" friend (see let. 4105, p. 199) in regard to lighting the gas by electric sparks from the finger. It is quite possible in this "Canada of ours;" but, so far as I know, only in the winter, in houses heated by steam, and of course only when the steam is on-that is, when the building is warm, at which time and in such honses much electrical amusement may be obtained, such as getting a shock when shaking hands, or when touching the brass knob on the steam radiator, &c. If in the winter any of your buildings in England are heated by steam please try the experiment. To light the gas no special preparation is needed, farther than first remove the glass globes (if any), then have some one near to turn on the gas-tap, as you must not touch glass or metal yourself when trying the experiment, now walk up and down the room a few times in your ordinary slippers, rubbing your feet on the carpet as you go, then approach the gas bracket, have the gas-tap turned on, carefully place your finger over the jet, but pointing down into without touching it; do not try the experiment with a crystal gaselier, as the metal pipe is usually disconnected. The truth of this I can prove in the strongest possible way if required. If your readers desire any experiments tried during the coming winter let them state clearly what they wish done, and, if not too difficult, we will try to carry out their suggestions.

I know that this experiment has been tried by competent parties in houses not heated by steam, but unsuccessfully.

Since writing above I have read the letter of "Traveller" (4168, p. 228), and beg to say that I am writing from Canada, and, to be more precise, I may say Montreal, where these facts are not known to all the intelligent persons. I refer, of course, to electrical sparks. I think "Traveller" must be mistaken in regard to the house being warmed by hot-air stoves; nor

do I think the presence of sharp frost or snow is needed further than at such times the steam would be sure to be on. His statements about shocks, rabber combs, &c., are quite correct.

I should be glad to have "Sigma" come out here next winter to investigate this matter, when we would introduce him to electrical and other sparks, give him send him home as "happy as a sand boy." some sleigh rides, tobogganing, snow-shoe tramps, and

MATHEMATICAL PROBLEMS. [4736.]-MAY I be allowed to make a suggestion which will be, I am sure, acceptable to readers of the ENGLISH MECHANIC? For some time past a chess problem has been weekly inserted for solution, and great interest has been taken in the chess department by many of our friends. I would suggest that a quarter of a column of your valuable space be devoted, in s similar way, to a mathematical problem every week, and to the best solution of the problem of the week before. The problems might be in geometry, algebra, trigonometry, mechanics, elementary differential calculus, &c.—that is, of such a nature and degree as to be of interest to mathematical students and mechanics who love to dabble in the science. The query to which I inclose an answer is a fair specimen of such a problem. I am sure such a mathematical corner would have a great attraction for very many readers. I should be happy to send, occasionally, problems of my own and of Cambridge friends, and should even be willing, for a few weeks, to look over and report on the solutions which would be sent. ALEPH.

INTERNAL RESISTANCE OF A BATTERY. [4789.]-WILL your correspondent "Pi," who notices my method for finding the internal resistance of a battery (as given on p. 859), kindly describe the methods proposed by Mance and Fitzgerald. I should then be able to judge as to their comparative advantages in practice. I may add that, supposing Thomson's reflecting electrometer to be at disposal, I have found that instrument by far the most rapid and accurate in practice for finding the resistance of s battery. It is merely necessary to note the deflection given with this instrument, and then to adjust a shunt to the battery until the deflection falls to onehalf, when clearly the resistance of shunt is that of the battery. I may note that I have tested my method (p. 859) with a reflecting galvanometer, and checked the result with the electrometer, with a satisfactory agreement. S. T. P.

P.S.-The remarks of "O." and others on matters connected with electric science are of general interest.

ON TUNING, AND REDUCTION IN THE SIZE OF MUSICAL INSTRUMENTS.

[4740.]-Ir is acknowledged by all that it is imposBible to tune any instrument perfectly where chords are required to be played on a fixed series of strings, pipes, or reeds. This has become so great a nuisance that I am surprised our makers have done nothing towards remedying it. Often have I heard that the piano and organ would be more enjoyable if they were only in tune, although it is remarkable how many instruments are allowed to remain in a painful state of discord, and, shocking to relate, are continually played apon, to the detriment of player and hearer. All this has been premised by the remarks of "F. R. C. S." on page 487, but I have thought on the subject, and believe something can be done by altering the construction and at the same time making a little sacrifice of perfection-viz., the present regular series having a string or other mediam for every tone. I do not believe in perfection in nature, but conceive that all our knowledge of perfection will be more utilised as we study imperfection and try to remedy it as far as we can. I shall now direct the attention of our

readers to the fact that there are two notes (not tones) in music that seldom if ever are played together. It matters little whether I take the old notation or any other notations to express my meaning. We must take the key note, and represent it by the figure 1, or by the term doh, or by a dot on or off a line. Now, this key note has another directly under it-for instance, the key C has B next to it, and although by our keyboard and notation no difference is apparent in the relative value or distance of such notes, yet in fact they are the closest or nearest to each other of all the notes in the scale of C. So again, if we take F for the key note, we shall find that E is the nearest in the scale of F, and if we take any other key we shall be sure to find the same rule in force. Do not mistake the note (or tone) above, for that is vastly different, and comparatively a long way off the key note. I have noticed that in ordinary music these two notes, being so closely together, are never used together, and I know of few instances in operatic or classical music where they are to be found so used: I think Beethoven and Mendelssobn to be the greatest users of this discord, but they could not afford this luxury very often. The question is, first, cannot this fact be taken advantage of, and next, could no more efficient tuning be produced by the method? Let us take a pipe or whistle with one hole, to be opened or shut so as to make the two notes, or a string with a lever to act like a finger to use open or shut, or a reed with an appliance for lowering the tone- when desired. These contrivances would have to act before the wind enters the pipe, or the hammer strikes the string, in fact, before the tone is produced, or we should hear two notes where one only is required. This is not so difficult as may be supposed, because the notes are so close together that we can play with them more than any of the others in the scale. A string may be played as tuned, although a piece of whalebone is placed lying on the string, when by a little pressure on the whalebone the next tone will be produced instantaneously. According to the pressure used, so would the tone be either higher or lower, and as much as the hole of the pipe was covered or uncovered so would the tone be again. If, then, this idea could be applied, so as to have only one medium for two notes, the size of our musical keyed instruments would be lessened one half, we should be able to play in tune, for every tone would be under the control of the player as in the violin, and we should be able to produce a better shake, trill, or thrill, than we can now, for in organ playing a good shake is impossible at present, while on the flute or clarionette it is quite practicable. I think the great defect in the violin is a weakness of tone, especially in solo playing or in out-door music. For this reason I thank "The Harmonious Blacksmith" for his new fiddle, and think that if the string could be made to move all the soundboards, a great effect would be produced; and as for the box principle, one piece down each side would convert the spaces quickly enough. A wire string might do, but a bow could not move the string; this without doubt is the difficulty.

I saw lately a piano which cost £100, whose strings were placed slanting instead of upright, with action to correspond, a most laborious piece of work. In another piano I observed that while the strings were upright, the grain of the soundboard was slantwise. The tone of the last is superior to that of the first, and it cost less than a third, besides being more simple in its construction. FIDDLER.

A HANDY ATMOSPHERIC BURNER. [4742.]-AN inverted funnel placed over an ordinary gas burner, resting upon a piece of wood with a small

FALL OF A BULLET. [4744.]-THE letter of Francis Lewis (4682, p. 541) deals with a new question. It was assumed that the figure of the earth was not to be considered. Practically it does not greatly affect the result, because if a cannon ball be fired horizontally from a place not much above the level of the ground, the range will not be great enough to give appreciable dip for earth's curvature.

A ball propelled fast enough might go round the earth, precisely as a cow's tail, if it were long enough, might reach to the moon. We can conceive these things. We cannot, however, conceive of those other motions which Mr. Lewis speaks of without first conceiving the law of gravity to be changed. Under gravity no ball could" revolve round and round the earth receding from it every revolution and part of a revolution." A

hole to admit it in the centre, as in sketch, will give an ball might recede continually, but in this case it would intense heat with little trouble of fixing.

TINTUB.

on until the six are fixed. The sides at the top and bottom will require paring so that the six may fit within the circumference of the rod. When the six are fixed and the glue dry, fix the rod in the lathe in the same prong-holes as before, with the long corner of the chisel cut through the swee ps top Band bottom until the rod is reached. Care must be used not to touch the brads; let them remain in, a touch with the hammer and punch will sink them below the surface. At be turned to allow a small collar to be fixed. The use the bottom a fillet or rabbet should the pillar may be put to is in every respect the same as that of an ordinary table pillar. A, the pattern; BB, the rod; C C, where to fix the sweeps. The length of the sweep may be varied to suit the fancy.

not go "round and round;" if it went once round it would then be at its starting point-no farther away under any circumstances whatever.

4691) there is nothing on earth to prevent him. They If" A., Liverpool," wishes to retain his views (let. are not likely to be very generally adopted. If they were, we should be put where people were before the are well worth studying, however. They show where laws of motion began to be recognised. "A.'s" letters beginners are likely to make mistakes. The writers of elementary text-books cannot too carefully note these than one would imagine to be possible. "A." will forpoints, for mistakes of the sort are much more common give my setting him as a "horrid example." One has no choice where the ill-informed do not ask for information but undertake to teach.

It would be a useful exercise for "A." to inquire what keeps a kite afloat in such a way that the string rises above the point of support. When he has obtained a just answer to this question he can return with advantage to his light globe tied to a string. He will then scarcely suppose that such a globe illustrates quite exactly (or at all) the motion of a cannon ball.

RICHARD A. PROCTOR.

OCEANIC CIRCULATION-CARPENTER v. MUHRY.

[4745.]-IN two letters, one of which appeared in the ENGLISH MECHANIC of October 6, 1871, p. 72, and the other in Nature of the previous day, p. 446, I showed that we were not justified in acceding to Dr. Carpenter's wish to have himself considered the original inventor of a certain theory on the above subject, but I regret to see a constant inclination on the part of English writers to ignore the statements that, in the cause of truth, I ventured to publish. Among those writers I Proctor, and I would ask him whether it is that he did particularly regret to see one so distinguished as Mr. not read my letters (the one in Nature appeared immediately under one of his own), or that having read them, and having consulted Dr. Mühry's pamphlet to which I referred, he found my conclusions incorrect. To turn a fishing-rod (common): Many of "our" readers may be aware that a goodly number of the articles on "Oceanic Circulation," where he regards I am led to my present remarks by Mr. Proctor's late woods most suitable are hickory, lancewood, and yew; theory in question. At the same time, while thus comcommon fishing-rods are turned in the lathe. The Carpenter, and not Mühry, as the originator of the but our amateur turners may turn a common rod from plaining. I must say that I fully recognise the ability ash sticks. I have turned a few out of ash. The wood with which he puts forward his general views on a most sold in bundles I found the best. We called them difficult subject; and we must all admire the genuine sticks. I paid about 1s. 4d. to 1s. 8d. per bundle, con- wit and reasoning with which he deals with a certain taining about twenty-five to forty sticks, varying accord-reviewer, and demonstrates the ignorance of an egotist. ing to the thickness. For the purpose of turning these rods a boring collar will be required, to be purchased for two or three shillings, fixed as shown in sketch. The centre of the hole in collar should be in line with the centre of the mandril nose, or it will be impossible to turn properly. The seating for the boring collar can be made of a piece of dry beech, cut out as described, and may be fastened with a wedge under the lathe-bed. The collar or plate should be fastened to the seating with a bolt and nut, for the purpose of shifting for larger holes. If the plate is properly made, when once in line with the headstock any sized hole may be used and still remain in line, as the centre remains still the same. One or two long augers will be required if any of the rods are required to slide one within the other. The cheapest plan is to purchase

a

four augers, say in., ĝin., fin., and lin., take them to a black. smith, tell him to cut them and strut a piece in, say 18in.; they will be handy at any time required. Those who do not wish to take the

SAMUEL SMITHER.

J. B.

Proctor's articles on the circulation of the water in the [4746.]-I HAVE read with much interest Mr. Atlantic, &c. He does not, however, give the cause for the principal motion, which seems to be the primary cause of all the subsequent surface currents-viz., the current which sets from the Gulf of Guines to the coast of Brazil. Perhaps he would kindly enlighten on this point, such of your readers as stand in need of the information with myself, in a future number.

IMPROVED BEEHIVES.

POPULARIS.

[4747.]-Thanks to Mr. Abbott for his letter (4502, P: 483). I should have written sooner, but waited for bis promised photograph and description. Reply 12450, p. 519, however, tells us to spell patience.

Thanks, likewise, to our Danish friend for noticing my difficulties (letter 4628, p. 511), and describing his centrifugal" honey-taker. This last, I cannot but Would some one think, might be much simplified. describe the American honey-taker which was said (p. 82, No. 866), to be a necessity to full success in bee management ?

In spite of thunder and rain this year seems likely, in some localities at any rate, to be a good bee year; if so, we may have to moderate the sanguine expectations which Mr. Cheshire (letter 4629) and others might lead young beekeepers to entertain.

I

E. T. GRAYS.

NEW DOUBLE STARS. [4748.]-As my observatory has been under repair, have hardly done anything with the telescope for the last few weeks. On July 20th, however, I managed to get a set of measures of Mr. Burnham's new double star 11 Scorpii, with the following results:-P = 78-20°, D 8.75". The double star 12 Scorpii, to which Mr. Barnham refers in his letter (4549, p. 462), was observed by the late Sir John Herschel, at the Cape of Good