words, might reply to both in one paper. Mr. Utting, after quoting from my answer to Glevum's question (on which he, as a matter of course, bestows bis usual quantum of notes of admiration), triumphantly exclaims (No. 251)-"Now, what does this imply, but that the ram must be in a state of quiescence ?" It is certainly true, that when the height of the pile engine is infinitely small, the ram will be in a state of quiescence. But my answer implies much more; it implies that labour has ceased. Therefore, when labour has ceased, it must, of necessity, be the least possible; but still there will be some effect from the pressure of the ram; and that effect will be the greatest possible, combined with the least loss of time and labour.

In the second paragraph, Mr. U. says "According to Mr. M.'s formula, the effect of a ram of one inch or one foot fall, in a given time, is. greater than that of a ram with a fall of ten feet; and until Mr. Mackinnon can prove this, I shall not be convinced of the truth of his theory." And does not Mr. U. say the same? Did I not bring forward Mr. U. himself to prove it? We will, however, examine him again, and endeavour to put the subject in a clearer point of view; and, if he is not more stubborn than the bed of the old river near Lynn harbour, I will wriggle it into him, inch by inch, from his own Table (page 7, vol. ix.), beginning with the lowest number in the Table. If we consider the labour of raising the ram to the height of one inch, as unity, the same numbers will express the height, and the labour of raising the ram to that height. We shall, also, consider the time employed in raising the ram to the height of one inch as an unit of time; and, for the greater simplicity, we shall consider the ram as unity. Then the same numbers will express height, time, and labour. Having assumed the ram as unity, the mo Imentum will be expressed by the velocity. Hence, if we divide the velocity by the numbers representing the height, time, or labour, we shall have that portion of the effect

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By looking at the Table, we perceive that a fall of one inch gives 2.315 as the effect produced by a unit of time and labour; by a fall of two inches, we have an effect of 1.637 for each unit of time or labour; by a fall of three inches, we have an effect of 1.3363 for each unit of time or labour; but by a fall of four inches, the effect for each unit of time or labour is reduced to 1.157, being only one-half of the effect produced by a fall of one inch,-which is in accordance with my former statement. Mr. U. may call all this assertion, if he pleases; there will be others, however, who will consider it a demonstration. Thus we perceive a constant decrease in the

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effect for each unit of time the higher we ascend, like an infinite series, without any chance of terminating, until we go beyond the sphere of the earth's attraction. If we descend lower in the scale, the ratio of the effect to the labour increases without any limits, until the space is exhausted, and then time and labour cease, and pressure is all that remains.

We now come to the postscript, where Mr. U. says "It appears evident to me that no formula will give a maximum effect of the ram on a pile, as so much depends on the nature of the soil it has to penetrate." The question has no max. ima or minima, to be sure; but that arises from the nature of the question, and not from that of the soil. What has the soil to do with it? Three inches of hard firm soil may have as great resistance as a yard of mud, but what of that? The driving of a pile three inches in the one, is equal to driving it a yard in the other; for an equal resistance has been overcome in each case by equal forces.

Mr. Glevum now claims my attention; but as he has left our differences to be decided by your readers, and seems inclined to withdraw from the contest, I will not press too hard on him in his retreat. Mr. G. seems to put an indirect question to me, when he "He has not thought says, fit, however, to enlighten us by the information as to what space it must fall through to acquire a double force." Here, however, Mr. G. is mistaken; for the equation which I gave (p. 286, vol. vii.), if applied, will enlighten Mr. G. in this parti cular. According to this equation, the space will be 0.062176 of a foot, or 746112 of an inch. The two authors alluded to by Mr. G. are Drs. Hutton and Gregory,-no mean authorities, I will allow: but if these authors make against me, they do still more so against Glevum. have, upon a former occasion, made some remarks on the first of these alleged quotations; I will now offer some remarks on the second, which Mr. Utting gives as follows (p. 6, vol. ix.) Dr. Gregory also in

I

forms us, in his Treatise on Me. chanics, that if the velocity of a hammer be equivalent to that which would be acquired by falling freely 10 feet, we shall have h10; and making w 12000 (magnitude of the impression), there will result half wh 60000; that is, the weight of the hammer will he to the force of pressure as 1 to 60000.” Had Mr. U. no notes of admiration to spare for the above quotation? Surely his stock must have been very low; for Mr. U. makes Dr. Gregory say, that the momentum of one pound, moving with a velocity of 25 364 feet in a second, is actually greater than that of one ton, with a velocity of 26.602. This is the way in which our best authors are abused. Mr. G., however, is mistaken, in supposing that I am not a practical man; and if he will only dismiss his impudent," ," "laughing" foreman, and put me in his place, I will prove it to his satisfaction. What with my theory and practice, and G.'s theory and practice, and the four lazy fellows, we shall work wonders. Let me, in the mean time, however, advise Mr. G. to use as heavy a ram as he can possibly manage: this he will find of great advantage in driving piles-in sand more especially. Whatever machine may be used in pulling up piles, I would advise that a man, with a mallet, be kept strik. ing side blows; this will be found of considerable advantage.

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I will now take my leave of the question for a season; trusting, that if any of your readers should find the above hints beneficial, they will communicate the fruits of their experience to the Editor.

I remain, Sir, Yours, &c.

A. MACKINNON.›

Shefield, July 29, 1828.

ON THE APPROACHING COMET. Sir,-In No. 262 of the "Mechanics Magazine," you have inserted, from the "Literary Gazette," a paper on the approaching comet, containing several palpable mis takes, which, with your permission, I beg leave to correct.

017 2 00.58680

Ditto

Ditto

Ditto

1759, Mar. 12 13 50 310 3 8 101

It does not appear that this comet was observed with sufficient attention to obtain the requisite data for computing its elements, previous to 1456, as they are not given in the Tables antecedent to that time. It will again, in all probability, pass its perihelion point towards the latter end of the year 1834, or the beginning of 1835.

The great comet of 1680 is supposed to be the same as appeared in the year A. D. 1106, 531, and fortyfour years before the Christian era, -its period of revolution being computed to be about 575 years.

The elements of this comet are widely different from that above given, its motion being direct, whilst that of the above is retrograde, and its perihelion point being in the opposite part of the heavens, or nearly 180 degrees distant.

"J. T. B." also gives the elements of the comet of 1758 as being

It is due to " J. T. B." to state, that in a subsequent Number of the "Literary Gazette," published on the same day as the Number of the "Mechanics' Magazine" in which the accuracy of his statements was questioned, he acknowledged the mistake into which he had fallen.-Edit. Mech. Mag.

the same with the above, but which it evidently is not; neither is it the comet of 1680, which is also equally evident.

In respect to the telescopic observation on the comet of 1780 (vol. x. p. 37), (I presume 1680 is meant,) that "it was, on Nov. 11, at 1 h. 6 m. afternoon, not more than one semidiameter of the earth to the northward of the earth's path," I have to observe, that Dr. Halley says, in the last page of the precepts to his "Astronomical Tables," that it came so near the path of the earth, that had it come towards the sun thirty-one days later than it did, it had scarce left our globe one semidiameter of the sun towards the north. See also "Long's Astronomy."

But as this comet will not return till about the year 2255, we need not at present alarm ourselves as to any direful events or universal conflagration to be produced by it!!

In respect to our gaining an additional moon, Laplace has proved that neither the moon nor any other satellite has ever been a comet; consequently, by parity of reasoning, no comet can ever become a satel lite.

It is hardly necessary for me to

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make any further comments on the remarks of your correspondent, his not being the same comet as the one expected, or that of 1759, which was distinctly visible, without a Telescope of very extraordinary powers. I am, Sir,

Yours, &c.

J. UTTING. Lynn Regis, Aug. 18, 1828,

Erratum.-Vol. x. page 43, col. 2, line 18, for "5,563,67," read 556 thousand 367 million million times," &c.

CORN DRYING MACHINE.

Considering the wetness of the present harvest time, it may be of seasonable use to a number of our country readers to be made acquainted with a very cheap, simple, and efficient apparatus for drying corn, a model of which was laid be fore the Highland Society at Glasgow, in 1826, by Mr. R. Monteith. The prefixed engraving represents. the construction of it so clearly as scarcely to require any explanation. From six to twelve sheaves being put on the forks of the middle ring or hoop, the whole are put in motion by a very slight degree of wind, and "when placed in an open situation," says Mr. M., " an hour of dry weather will completely dry them, after having been drenched with rain."

When time presses, and a sufficient number of such machines are not in readiness, the following mode of

harvesting, recommended by a correspondent of the "Times," and which may be had instant recourse to by every one, is deserving of adoption:

Let a stake of six feet six inches in length be driven about six inches into the ground, eight sheaves be set up around it, and a large hood sheaf be firmly transfixed upon the top of the stake. The stake will prevent the wind, however violent, from displacing the hood sheaf; the air will have free access to the corn of the lower sheaves; the great expense and attention at present attendant on replacing sheaves, when blown down, will be avoided; and a perfect security obtained against the germinating of the corn. "If every farmer," says the writer who recommends this practice, "provide in due season a number of stakes proportionate to the extent of his crop, he may be assured, however wet the weather may prove during harvest, that by their application he will avoid having any unsound corn,"

1. The protractor, which ordinarily is divided into whole degrees only, but in this into halves.

2. The trigonometrical and dialling scales,. which comprise, in four lines, all that are essential,-viz. chords, sines, tangents, secants, latitudes, and hours. These are all laid down to a radius of 18 inch, being the largest that a six-inch scale will admit. For the line of rhumbs, that of chords may be used as a substitute, by calculating 114° for one point: also for the line of Incl. Merid., that of hours will serve