1440 1316:394 123-606 lbs.; or 1-5457 bushels.

An article so important as coal to our domestic comfort, and so essential to all the grand purposes of steam locomotion, artificial light, and national manufactures, should be subject to no restraints in respect to the mode of transit-should be placed beyond the reach of monopoly, whether arising from petty jealousies or aristocratic pride; and should, moreover, be liable to none of those flagrant abuses which are inseparable from the present system of delivery to the consumer. Taking the foregoing observations as data, it will be found that the average loss sustained, on the several kinds of coal I have enumerated, is very nearly 9 per cent.

Δ.

MECHANICS' INSTITUTION LECTURES.

Sir,-Colonel Torrens, it appears, is about to follow the example set by Sir Robert Wilmot Horton a year or two ago (just previous to his leaving England to take possession of his post as governor of Ceylon), by delivering a course of lectures to the members of the London Mechanics' Institution, on "the causes which regulate the value of the wages of labour." Yet, notwithstand. ing these two authorities in favour of the practice, it may very fairly be doubted whether political economy is a fitting subject to be handled in popular lectures. The extensive and abstruse nature of the science, and its utter inaptitude for illustration by experiment, seem at once to point out the necessity of its cultivation in the quiet of the study, rather than amid the uproar of the crowded theatre. The Colonel's prime object is to convince his hearers of the utter futility, in natura rerum, of the Trades' Unions, or any other species of combination among working men. But

is lecturing the way to do this? Are those men, whose minds can be con vinced by the few passing, half-forgotten words of a lecturer, who has "all the say to himself," worth the trouble of convincing at all? If they are, it is now too late, for they must have made up their minds long ago, after hearing the very eloquent, impartial, and dispassionate harangues of a gentleman, who preceded both Sir Wilmot and the

103 Colonel, at Southampton-buildings, the celebrated Mr. Thomas Hodgskin!

The mania for taking a short cut to knowledge, by the hearing of lectures, has, indeed, now risen to so great a height, that not a moment's consideration is ever given to the questionwhether the subject is a proper one for the purpose? All seem to be regarded as equally eligible. This is, certainly, no trifling mistake; and, unfortunately, our Mechanics' Institutions, which might be expected to stick more closely to scientific subjects than the similar establishments of a more general and " genteel" character, have gone as far out of the road as the best-or the worst-of them. Thus, at some that might be named, the mechanic has been enlightened by a series on such very edifying and instructive matters as "The History of Chivalry," or "The Poetry of the Middle Ages,"-glaringly inappropriate as they are, and thoroughly unsuited for the purposes of the lecturer, from the impossibility of exciting the hearer's attention by striking experiments, owing to their unexperimental nature. More ridiculous fooleries even than these have been sometimes perpetrated:-a dry old Chancery barrister has been engaged, and that, too, at institutions, not a hundred miles from the metropolis, in diffusing useful instruction in science,"

by the delivering of certain very grave lectures on the important subject oflaughter,-duly interspersed with a very extensive, if not judicious, selection, of the most venerable Joe Millers in existence! What would our simple ancestors have thought, could they have foreseen so much of the march of intellect as this!

Greatly as lecturing has progressed, in quantity, within these few years, a great deal might still be done in the improvement of the article in quality; but the first thing to be effected should be, the banishment from the theatre of all those subjects-an immense number-on which more information might be gained by reading for an hour, than by dancing attendance on a very nice man for a month. Those retained would be, of course, only those which require an expensive apparatus for their illustration, or which admit of very striking exemplifications of the facts laid down-such, for instance, as astronomy and chemis

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try. Even the lecturer on the latter science, the best adapted, perhaps, of all, for display before a large assembly, finds many difficulties in his path. An experiment which succeeds perfectly in the laboratory, sometimes, from the heat of numerous breaths, or other causes, fails entirely in the well-filled lectureroom-and thus a fact, which ought to have been irrefragably proved, is left a bare assertion, and the almost solitary advantage possessed by a lecture over a pointed essay is wholly lost. This is not, by any means, a slight drawback, for it often happens that the failures are more numerous than the successful attempts. There is no danger of these mishaps, indeed, in lectures which consist of "all talkee-talkee;" but then, as these possess no advantages whatever, the exemption is of little consequence.

It might, perhaps, be a good thing to introduce an article in the rules of Mechanics' Institutions, excluding all lectures on subjects not strictly scientific; with a special proviso into the bargain against political economy, however high in the world the lecturers might be. I remain, sir,

Yours, respectfully,
F. H.

London, May 8, 1834.

ROTATION OF THE EARTH.

Sir, I have derived much pleasure and instruction from the perusal of Mr. Lyell's interesting work on geology, and have been duly impressed by the force of reasoning through which the author arrives at the conclusion, that the amount of depression of the more ponderous elevated parts of the earth's surface exceeds that of the elevation of similar depressed parts. It also seems probable that, from the escape of internal heat, the dimensions of our planet have in some degree contracted, and that they may be still in an actually contracting state. This supposition, however, and also the opinion that the amount of the depressions on the earth's surface exceeds that of the elevations, is opposed, as Mr. Lyell observes, by the arguments of La Place, who shows that such a circumstance could not occur without a sensible diminution of the period of the earth's diurnal rotation, such mechanical effects

being the necessary consequences of a given rotary impulse imparted to a body whose quantity of matter, and of course of inertia, remains undiminished, -notwithstanding its dimensions may have contracted. This would seem, indeed, to amount to a proof that both the opinions alluded to, however plausible they may appear in theory, and however countenanced by other circumstances, are really unfounded in fact.

But there is a circumstance attendant upon the rotation of the earth, of which I have not observed any notice to have been taken by philosophers, which it appears to me must have a constant, though minute, tendency to increase the period of the earth's diurnal motion; and if this tendency to increase that period should be equal to the opposite tendency proceeding from the causes spoken of in Mr. Lyell's work, the two tendencies would balance each other; or, if unequal, the difference only would have to be accounted for. In the case of equality, the arguments of La Place, as opposed to Mr. Lyell's hypothesis, are superseded, and if unequal, the difference may be so minute as not to be sensible during the period adverted to by the late distinguished philosopher of France.

In order to put my ideas in a clear point of view, let our planet be supposed to consist entirely of fluid matter, and revolving as at present, in that case the attraction of the moon would always cause the diameter directed towards that satellite to be greater than any other, and every particle of the whole fluid mass would, with respect to its own centre, be in a constant state of alternate elevation and depression; these alternations, it is true, would, in a gravid point of view, balance each other, but there would be nothing to compensate the loss of mechanical power proceeding from the constant friction of the particles of the fluid among themselves. Now, as this friction must always operate as some impediment to the change of figure constantly taking place in the fluid planet, as regards the relative position of its component particles; and as that change of shape is an unavoidable concomitant of the diurnal motion, and also as it is clear that the loss of power by the friction above mentioned inust be at the expense of some existing mechanical power, and as there is no other mechanical

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to be fitted with the utmost nicety. Keys and wedges are also requisite_to keep them in their proper places. But although great care and skill are gene rally shown in their construction and adjustment, the quantity of friction is still so considerable, as to be a serious drawback on the efficiency of the engine. I beg, therefore, to submit to the consideration of your readers a remedy for these complicated levers; it is similar in principle to the guide used in high-pressure engines, and will be easily understood by reference to the accompanying figures.

Fig. 1 is an end view of the engine, and fig. 2 is a front view of the guide (the other parts it is unnecessary to represent). In fig. 1 A is the steam-cylinder. B a steam passage. C the stuffing-box. D the piston-rods connected to the horizontal-rod G Y. ee are the straps, in their usual situation. f the end of the beam. H, H, the guide. Fig. 2, is the end of the rod G (in fig. 1). H, H, is the guide, and j is a hard piece of wood (or iron) to form a solid base to the guide.

Dec. 30, 1833.

I am, Sir, yours, &c. MASHDOUD MOHANDEZ.

MR. SAXTON'S LOCOMOTIVE-PULLEY. Sir, If any thing could justify the terms in which your correspondent, Mr. Adams, impugns Mr. Saxton's locomotive-pulley, it is the circumstance that he has had the manliness to put his name to his communication; and yet, both in justice to himself and to Mr. Saxton, he should have been quite certain that he perfectly understood the invention and its application, before he permitted himself to say of it, that "it is founded in ignorance of the principles of mechanics."

The model with which Mr. Adams' experimented appears to have been very imperfectly constructed, for he speaks of a weight of 135 ounces requiring 2 ounces to propel it on a common level railway, which makes the draught from friction to be 1 in 67, instead of 1 in 200. His experiments also do not appear to have been very carefully conducted, or perhaps they were vitiated by the excessive friction; for he says, that when his railway was made to rise 7 in 8, "he

found it required 12 times the power of propulsion at that acclivity that would suffice upon level ground." Now this proportion depends upon another, that of the friction to the weight. If he had taken results found in actual practice for his data, he might have said, that the power required in such case was more than 20 times instead of 12 times greater; he has, therefore, understated the unfavourable view he has taken of the subject.

However, let those two points pass, and let us proceed to "the fundamental objection," and the fatal one too, if it were correct, which Mr. Adams advances against the principle of the invention, "The whole action," he says, "consists

This

of nothing but friction;" and he illustrates this assertion by his experiments, by which it appears, that whatever power is employed to propel a carriage upon a level railway, 25 times that power is required to propel it upon Mr. Saxton's plan. Now it may be very true, that his experiments showed this proportion, for we are not informed what relation the diameters of the two pulleys bore to each other; but the inference from this is not, as Mr. Adams supposes it to be, that 25 times extra power is required, in order to overcome 25 times greater friction, but that there is a capacity in the machine to effect 25 times greater velocity, the propelling force travelling in each case at the same rate. power is converted into velocity, a circumstance which he entirely overlooks, and not uselessly expended upon " friction-machine," as he strangely supposes.* He of course must be aware that Mr. Saxton does not pretend, as do others, to generate the high velocity at which he aims (30 miles an hour), in a perpetual-motion fashion. Mr. Adams, therefore, should have shown, in disparagement of the invention, that the velocity is obtained in a more circuitous manner, and at an expense of a greater waste of power by friction or otherwise, than by any other known method; a task which he would have found very difficult to execute. In fact he is without

It is not to be supposed that in this, any more than in any other mode of producing a great locomotive velocity (the resistance from friction being alone considered), that it is obtained, theoretically speaking, only by a great expenditure of power, for the time of performing a given distance is inversely as the velocity.