mosphere did in Newcomen's engine, has also been applied to the forcing it up; by which means, engines, where cylinders are of a given diameter, are now made to perform double the effect. This has not only saved great expence in the original construction of the engines, but has enabled them to be applied in cases where immense power has been wanted, and which could not have been performed at all by them on Newcomen's construction. By the same mode of applying the steam, it can now not only be used of the strength of the atmosphere, but as much stronger as necessity or convenience may require; which is a still farther consolidation of the power. The celerity also with which the condensation of the steam, and the discharging of the condensed steam and water, are performed, enables them to work quicker, and so to be applied to all kinds of mill work, which are used in the numerous manufac tories of this country. Corn is ground by them, cotton spun, silk twisted, the immense machinery used in the new manufactories are worked, and including every kind of mill work to which water can be applied. They are also used in the various branches of the civil engineer. Thus the water is taken from the foundations of Locks, Bridges, Docks, &c. The piles are driven for the foundations, as the mortar manufactured for the building of the walls; earth taken from their canals; and docks and works have been of late performed by their means, which could not have been executed without them." Vol. II. p. 107.

One of the most entertaining parts of this volume is that which is dedicated to the various optical problems, and experiment, which are given at considerable length. From these the reader may acquaint, himself with the principle of the phantasmagoria and other exhibitions, which have in their day so much interested the public. At the conclusion of the volume, a very amusing account is given of all the various echoes and their most remarkable phænomina. We can speak also in terms of approbation of Dr. Hutton's acousties, and of his account of the Grecian music; the latter part however of this section is rather too dry to be studied by any one but a professed musician.

The third volume present us with all the elementary problems in astronomy, geography, dialling. A very interesting chapter upon navigation occurs in this work, which will prove full of practical information even to the most ignorant of the first principles of the art. To this succeeds a very clear and useful account of the mode of constructing arches and bridges; and at the conclusion of the volume, the reader is presented with all the various methods of making rockets and other fire-works, and is made acquainted with the principles upon which they are constructed. As many of our readers must be unacquainted with the cause of that rapid ascent of rockets which they have so

often

often with astonishment witnessed, it will be interesting to them to know the principles by which their flight is directed.

"As this cause is nearly the same as that which produces recoil in fire-arms, it is necessary we should first explain the latter.

"When the powder is suddenly inflamed in the chamber, or at the bottom of the barrel, it necessarily exercises an action two ways at the same time; that is to say, against the breech of the piece, and against the bullet or wadding, which is placed above it. Besides this, it acts also against the sides of the chamber which it occupies; and as they oppose a resistance almost insurmountable, the whole effort of the elastic fluid, produced by the inflammation, is exerted in the two directions above mentioned. But the resistance opposed by the bullet, being much less than that opposed by the mass of the barrel or cannon, the bullet is forced out with great velocity. It is impossible, however, that the body of the piece itself should not experience a movement backwards; for if a spring is suddenly let loose, between two moveable obstacles, it will impel them both, and communicate to them velocities in the inverse ratio of their masses: the piece therefore must acquire a velocity backwards nearly in the inverse ratio of its mass to that of the bullet. We make use of the term nearly, because there are various circumstances which give to this ratio certain modifications; but it is always true that the body of the piece is driven backwards, and that if it weighs with its carriage, a thousand times more than the bullet, it acquires a velocity, which is a thousand times less, and which is soon annihilated by the friction of the wheels against the ground, &c.

"The cause of the ascent of a rocket is nearly the same. At the moment when the powder begins to inflame, its expansion produces a torrent of elastic fluid, which acts in every direction; that is, against the air which opposes its escape from the cartridge, and against the upper part of the rocket; but the resistance of the air is more considerable than the weight of the rocket, on account of the extreme rapidity with which the elastic fluid issues through the neck of the rocket to throw itself downwards, and therefore the rocket ascends by the excess of the one of these forces over the other.

"This however would not be the case, unless the rocket were pierced to a certain depth. A sufficient quantity of elastis fluid would not be produced; for the composition would inflame only in circular coats of a diameter equal to that of the rocket; and experience shows that this is not sufficient. Recourse then is had to the very ingenious idea of piercing the rocket with a conical hole, which makes the composition burn in conical strata, which have much greater surface, and therefore produce a much greater quantity of inflamed matter and fluid. This expedient was certainly not the work of a moment." P. 389.

In the fourth volume Dr. Hutton details all those experiments which explain and illustrate the properties of fluids, with a variety of miscellaneous problems in natural philosophy, magnetism, electricity, and that most curious of all physical phenomena, the divining rod. There is a peculiar property, it would appear, residing in certain constitutions, which enables the possessor, upon taking a hazel, or some other twig, to discover a spring below the surface of the earth. Upon the arrival of the person endowed with this faculty upon a spot where water is to be found, the twig will be found to twist itself in the hand. Upon a bridge, or in a boat, no effect is perceived; the water must be under ground to produce the phenomenon. Dr. Hutton gives an account of a lady, who, in consequence of an article in a former edition of his translation of Montucla, sent a message to him, offering to shew an instance of this extraordinary faculty in her own person. This was a lady of rank, who, of course, did not choose that her name should be inserted in a publication like the present. The following is the relation of the fact, to which Dr. Hutton was a witness:

Accordingly, at the time appointed, the lady, with all her family, arrived at my house at Woolwich Common; when, after preparing the rods, &c. they walked out to the grounds, accompanied by the individuals of my own family and some friends, when Lady showed the experiment several times, in different places, holding the rods, &c. in the manner as described in her ladyship's first letter above given. In the places where I had good reason to know that no water was to be found, the rod was always quiescent; but in the other places, where I knew there was water below the surface, the rods turned slowly and regularly, in the manner before described, till the twigs twisted themselves off below her fingers, which were considerably indented by so forcibly holding the rods between them. All the company present stood close round the lady, with all eyes intently fixed on her hands and the rods, to watch if any particular motion might be made by the fingers; but in vain, nothing of the kind was perceived, and all the company could observe no cause or reason why the rods should move in the manner as they were seen to do. After the experiments were ended, every one of the company tried the rods in the same manner as they saw the lady had done, but without the least motion from any of them. And in my family, among our'selves, we have since then several times tried if we could possibly cause the rod to turn, by means of any trick or twisting of the fingers, held in the man

ner the lady did; but in vain, we had no power to accomplish its The annexed figure represents the form and position of the rod, about 6 inches in length, cut off just below the joint, or junction of the two twigs

6. I am

"I am sorry it is not permitted to publish the lady's name. While this edition of the book was in the press, thinking the above particulars might form no improper supplement to what had been said by M. Montulca on this subject, I addressed a few lines to Lady, then in a distant part of the country, to enquire if her name might be mentioned in the account I meant to give; to which I received the following answer in the negative.

Dear Sir, Oct. 30, 1813. "Having been from home, I did not receive the favour of your letter till yesterday, therefore take the earliest opportunity of replying to it. As I have ever had a horror of appearing in print, I had rather not have my name given with the account you propose of the discovering of springs; therefore, as it will be anonymous, you will judge for yourself how far you may wish to relate the circumstances with which I have acquainted you. They are known to so many, that I am of opinion they will obtain credit in a great degree, without a name being formally attached to them. I can only repeat, that every experiment I have made confirms the reality of the power, though I cannot account for it." P. 229.

To the testimony of such a man as Dr. Hutton, we can raise not the slightest objection; he could not in such a case be desirous of deceiving the world, and the evidence of his senses could not have deceived himself. We believe, however, that there are persons in sufficient number, besides the lady who exhibited the phenomenon to Dr. Hutton, who possess this power to warrant our belief. It is a faculty, as we understand, that resides chiefly in families; which would lead us to suppose that there is something in the natural construction of the frame, which produces so extraordinary an effect, although the mode in which it operates must remain unexplained. It might be with reason supposed, if we might hazard a conjecture, that it is some property existing in the nervous system: we know the agitation in which certain persons are thrown when certain objects of natural antipathy are near their persons, such as apples, cats, spiders, &c. although it is ascertained that they were wholly unconscious from their outward senses of their presence. We therefore can see no reason why the presence of a spring below the earth should not agitate in a similar manner the nervous system of certain individuals, so as to twist a hazel twig in their hand, while they are in a similar manner unconscious of its nearness to their person.

Of that part of the present volume which treats of chemistry, we cannot speak in terms of equal approbation. It is clear that Dr. H. possesses but a very confined knowledge of the subject.

The

The terms are often both confused and inaccurately applied, nor is there any thing satisfactory throughout the whole, except a few common experiments, which cannot be sufficiently enjoyed from ignorance of the principles upon which they are conducted. This is the only part of the four volumes which we could wish to see reconsidered and recast. An experienced chymist would in the same number of pages furnish a general view of the chemical science, and propose an equal number of useful and entertaining experiments, subjoining to each a rational and satisfactory explanation.

Many of Dr. Hutton's remarks upon natural phenomena are exceedingly ingenious; as a specimen of these we shall present the reader with his reason for a fact, to the existence of which we can all bear testimony.

"What is the reason that the bottom of a vessel, which contains water in a high state of ebullition, is scarcely warm?

"Before we attempted to enquire into the cause of this phenomenon, we thought it proper first to assure ourselves of the fact, for fear of exposing ourselves to ridicule, like those who explain in so ingenious a manner the phenomenon of the child in Silesia with the golden tooth; a phenomenon however which was only a deception, as well as that which occurred to the marquis of Vardes, explained with so much sagacity by Regis, and which however was the trick of a servant. And the case is the same with many others, which ought first to be confirmed, before we attempt to explain them. We brought water therefore to a strong state of ebullition, in an iron vessel, and having touched the bottom of it, while the water was boiling, we indeed found that it had but a very moderate heat; it did not begin to be burning hot, till the moment when the ebullition had almost ceased.

But

"In our opinion, this effect is produced in the following manner: we have already shown, that the ebullition is occasioned by the pellicle of water, which touches the bottom of the vessel, being continually converted into vapour. This conversion into vapour cannot take place, without the bottom always losing some of that heat, which it acquires by the contact of the coals or fire. during the interval between the moment when the vessel is taken from the fire, and that when it is touched, as no new igneous fluid reaches it, though it still continues to boil, it is probable that the remainder of this fluid is absorbed by the water which touches the bottom, and which is converted into vapour.

"Without giving this explanation as absolutely demonstrative, we are strongly inclined to think that such is the real case; and what seems to give it more probability is, that while the bottom of the vessel, from which the boiling proceeds, is but little hot, the sides have the heat of boiling water so that the finger would be E e burnt,

VOL. III. APRIL, 1815.