we believe, the first attempt to explain its operation on philosophical principles.

The following will give the reader an idea of the propositions maintained in it; 1. It is said, that, in the generator, or high-pressure boiler, the heat is greatest at the top, and decreases towards the bottom, against which the flame and heat of the furnace are chiefly directed; so that while the temperature of the upper parts of the boiler is at 400°, that of the lower parts next the fire may, in extreme cases, be so low as 40°. 2. Although the water exposed in this manner to the intense heat of a furnace, remains permanently cold, yet, if any crack or opening should take place in the bottom of the boiler within which the water is pressed with a force of at least 400 lb. on the inch, no water will issue at the opening. The reason assigned for this, we are unable to comprehend, or to render intelligible. 3. It is proposed "to pump back the heat" into the boiler, after it has done its office of impelling the piston in the cylinder; to pump it back into the generator, and to cause it in this way to act again and again upon the piston; so that, in this manner, the author, in the fervour of his imagination, thinks it but reasonable to expect, that an apparatus of this kind may be constructed, which, when once sufficiently heated, will continue to move for ever, and to drive machinery of itself, without any farther consumption of fuel. On looking into his description of this part of the apparatus, we find the plan consists merely in heating the water of the generator by the waste steam from the cylinder,—a plan which has been already frequently proposed, and which is indeed practised to a certain extent in every steam-engine in the kingdom.-Jameson's Journal.

Singular Effect of Heat on the Colours of Glass.-In a memoir on rare minerals, published in the Memoirs of the Physical Society of Geneva, tom. i. part ii. p. 471, M. Soret mentions some curious facts respecting two kinds of glass employed by MM. Dumas and Raisin of Geneva, in giving the tints to artificial topazes.

One of these glasses, or pastes, is of a bright yellow colour, similar to that of the corundum, commonly called oriental topaz. When this glass is reduced to small fragments, and exposed to the action of the fire, it assumes in succession the following colours, viz. bright yellow, orange yellow, orange, orange red, violet red.

Another paste, of an aqua-marine blus colour, or a bright blue, passes, by the application of an increasing heat, from bright blue to bright aqua-marine green, and then to yellowish green. In cooling, the glass returns to its first tint through the same tints. If the fire is pushed to red heat, the yellowish green tint becomes a bright yellow, and finally an orange yellow. This last colour is permanent in the glass after cooling. M. Soret quotes the analogous experiments of Dr. Brewster on the ruby, and those of M. Berzelius on different metallic glasses.-Brewster's Journal.

Mr. Barlow's Neutralizing Plate.--We are happy to learn that this eminent natural philosopher has received the highest reward, viz. that of £500, given by the Board of Longitude, for his plate for neutralizing the action of the iron of ships in producing a deviation in the compass.

The centre of a small circular iron plate is placed in the line of the attraction of the ship's iron, and at a proper distance behind and below the pivot of the compass needle, the position of this line having been ascer tained previously to the ship's leaving port, an operation which will be greatly facilitated by a table for this purpose, prepared by Mr. Barlow. When this is done, the needle will remain active and vigorous in the polar regions, and will direct itself in the true magnetic meridian, in whatever part of the world the ship is placed. This effect of Mr. Barlow's invention has been experi mentally established between the 61° of south latitude and the 81° of north latitude, by the accurate observations of Lieutenant Foster, and by other naval officers. There

are few scientific inventions of modern times more truly beautiful in principle, and more useful in practice, than this of Mr. Barlow's.-Ib.

Mr. Scoresby's New Experiments on Magnetism.-Mr. Scoresby had formerly shown, that bars of steel could be rendered highly magnetic by hammering them in a vertical position, with the lower end resting upon a poker or rod of iron. This process, however, he has greatly improved by hammering the steel bars between two bars of iron. The steel bars were the eighth part of an inch in diameter.

When only one bar of iron was used, a steel wire, six inches long, lifted a nail weighing 186 grains; but when two bars of iron were used, the wire lifted 826 grains. When the new process was em

ployed with an iron bar eight feet long, a steel wire six inches long lifted 669 grains, or four times its own weight.

Mr. Scoresby's theory of this process is, that percussion on magnetizable substances in mutual contact inclines them to an equality of condition, in the same manner as all bodies of different temperatures tend to assume the same temperature when in contact. The two great iron bars being made magnetical by position, the interposed bar of steel will therefore, when thrown into a state of vibration by percussion, receive a portion of their magnetism. In like manner a magnet, when struck in the air with a piece of flint, or upon a body of inferior magnetic quality, will have its magnetism diminished.-Ib.

Aurora Borealis imitated by an ElectroMagnetic Experiment.-M. le Chevalier de Nobili, of Modena, the author of this experiment, took a large metallic wire, covered with silk, and coiled it up so as to form a spiral plate, with 24 turns, the wire of one turn being always in contact with the adjacent one. When a weak electrical discharge is made to pass through this spiral plate, a light is seen to proceed from the centre of all the spires. It resembles artificial fire, and is very distinctly visible without darkening the chamber in which the experiment is made. When the wire is coiled up in a rectangular shape, a very faint light is seen. M. Nobili considers this last as the ordinary electrical light, and the first as electro-magnetic, as it is displayed only in the case when electricity exerts a magnetic influence. M. Nobili has announced a work entitled Questions sur Magnetisme, in which he discusses all the recent discoveries in that science. See Bibliothèque Universelle, Jan. 1824, p. 39.

On the Combustion of Iron by Sulphurous Vapour.-Professor Hare has observed, that if a gun barrel be heated red hot at the butt end, and a piece of sulphur thrown into it, a jet of ignited sulphurous vapour will issue from the touch-hole, when the mouth of the barrel is closed with a cork, or when it is blown into. He found that a branch of iron wire, exposed to this jet, will burn as if ignited in oxygen gas, and will fall down in the form of fused globules, in the state of proto-sulphuret. When hydrate of potash is exposed to the jet, it will fuse into a sulphuret of a fine red colour.-Dr. Hare's Letter to Professor Silliman.

Mountain Tallow.-Specimens of this mineral substance were lately found in a bog

on the borders of Loch Fyne. This curious mineral was first observed by some peasants on the coast of Finland in 1736; afterwards it was found in one of the Swedish lakes. M. Herman, physician at Strasburgh, observed a similar substance in the water of a fountain near that city; and Professor Jameson met with it in this country. It has the colour and feel of tallow, and is tasteless. The following notice in regard to it was sent to us:-It melts at 118° and boils at 290°; when melted, it is transparent and colourless; on cooling, becomes opaque and white, though not so much so as at first. It is insoluble in water, but soluble in alcohol, oil of turpentine, olive oil, and naphtha, while these liquids are hot, but it is precipitated again when they cool. Its specific gravity in the natural state of it, is 0.6078; but the tallow is full of air-bubbles, and, after fusion, which disengages the air, the specific gravity is 0.983, which is rather higher than that of tallow. It does not combine with alkalies, nor form soap. Thus it differs from every class of bodies known;-from the fixed oils, in not forming soap:-from the volatile oils and bituments, in being tasteless and destitute of smell. Its volatility and combustibility are equal to those of any volatile oil or naphtha-Jameson's Journal.

Extraordinary extent of the Baize and Flannel Manufacture at Rochdale." In the town of Rochdale, and the adjacent villages, there are manufactured, every week, of flannels and baizes, about 20,000 pieces, of 46 yards each, making 47,840,000 yards per annum. It is supposed that 17,840,000 yards are exported; the remaining 30 millions of yards are consumed in the United Kingdom, being an average of about 14 yards for each individual. Some good flannels are manufactured in Wales; a few coarse ones at Keswick, and some other towns and villages in the kingdom. A few are manufactured on the Continent, and works for that purpose are now erecting in America; but the whole of the flannels manufactured on the globe, besides those manufactured in Rochdale and its immediate vicinity, are not equal in quantity to those made there. The price of flannels is from 5d. to 3s. per yard; and the average may be stated at from 13d. to 14d. per yard; so that the annual value of the manufacture may be stated at about three millions Sterling. The wool costs fully onehalf of the wholesale selling price; the oil, labour, and finishing, &c. constitute nearly the other half."

Mr. Wilson's Report.

"If the Lectures on Arithmetic had any marked peculiarity, it was that of leading the student to trace every operation which he was required to perform, to some established principle. The utility of such an exercise is too obvious to require any illustration, since it is a matter of experience to all who are engaged in conducting business, that the technical rules given in the ordinary Treatises of Arithmetic for the solution of practical questions, can rarely or never be employed. It is not meant to be insinuated that the formal mode of procedure adopted in the majority of our seminaries ought to be abandoned; but it is contended that the mere circumstance of the scholar being able to follow the routine prescribed, is an attainment of comparatively little value, unless he perceives the principles on which the rules are founded. The first object, therefore, constantly kept in view throughout the course, was to place distinctly before the understanding of the student, the precise nature of the operation to be performed; and having explained the ordinary manner of procedure by a reference to these principles formerly illustrated, to leave him to the unfettered exercise of his own judgment in discovering by what path the conclusion might be more speedily attained. To render this part of the subject more interesting, recourse was had to the palpable symbols formerly procured; and both the Roman Abacus, and Chinese Swanpan were exhibited.

"After a very full explanation of the principles of Algebra-a portion of science entirely new to the great majority of the students, their attention was particularly directed to the doctrine of chances a subject adverted to in a very cursory manner last year; and regarding which, no information is to be found in the most popular elementary treatises. The subject, however, is one of great practical importance; for without some acquaintance with the leading principles of this doctrine, the method of estimating the value of annuities for life, of calculating the premiums on insurances, &c. cannot be understood. In the in

vestigations connected with this subject, an opportunity was afforded of demonstrating the ruinous nature of all speculations in lotteries and other games of chance, however flattering the prospect of success, and also of showing that it was only by calculations founded on the principles unfolded in this science, that Benefit and Friendly Societies can be formed on a secure and permanent basis.

"In the department of Geometry, the truths demonstrated, were illustrated by means of palpable diagrams. The textbook placed in the hands of the students, contained demonstrations of the several theorems; but these sensible representations were found to be extremely useful in conveying accurate ideas of the truths enunciated, and in impressing them more deeply on the mind.

"It is not easy to state the precise number of students who attended the Mathematical Class. Generally speaking, the attendance was somewhat less numerous than during last session, but it was much steadier. The average may be reckoned from 150 to 200.

"At the commencement of the session, an attempt was made to classify the students, by assigning particular seats to those who were desirous of directing their chief attention to Mathematical Science. This arrangement was adopted with a view to ascertain the regularity with which the Lectures were attended, and likewise on account of the great facilities which it afforded for the examination and correction of exercises. To each seat one of the students was appointed Inspector, whose duty it was to collect the exercises of that seat to which he belonged-to examine and correct them if necessary, and afterwards return them to their respective authors. The person selected to fill the office of Inspector, was he who had excelled in the performance of exercises, and who was therefore best qualified to undertake the duty. It is almost unnecessary to add, that this duty was most cheerfully performed by all the individuals so appointed, although many of them can devote but a very small portion of time to scientific pursuits.

It was left entirely to the students to

comply with this proposed arrangement, according to their own discretion; but upwards of 70 gave in their names as desirous of having seats assigned them, and the average number of exercises performed by each (exclusive of the prize exercises) was 19.

A

"As several individuals who attended the Mathematical Class during the former session, bad again entered as students of the SCHOOL of ARTS, it was judged expedient to devote another hour a-week for their instruction. The course of Plane Geometry through which they had passed, being in several respects incomplete, it was necessary to take a short review of the principal propositions formerly demonstrated. The elements of Trigonometry, the most useful problems in Mensuration, and the nature of Logarithms, were afterwards explained. The construction of the Sliding Rule, so useful to practical Mechanics, was then shown, and a few of the students constructed Rules for themselves. great variety of questions were proposed in the Class, so that every one became expert in the solution of the simpler problems. It was intended, at the outset, to have demonstrated the simpler properties of the Conic Sections; but as the session was so short, it was considered more expedient to confine the attention to objects of practical utility. The few weeks that remained, were therefore employed in pointing out the construction and manner of using the ordinary instruments for Land-Measuring, Surveying, Levelling, &c.; and as the institution is now provided with an excellent Theodolite, a few of the students were occasionally employed in measuring the heights and distances of several prominent objects in the neighbourhood of the city.

"The attendance at the second Class was, of course, much less numerous than at the first, with the exception of the first three or four Lectures, when, as was to be expected, many attended who were quite unable, from their want of the requisite preparatory knowledge, to derive any benefit from such prelections. The number of regular attenders fluctuated between 30 and 50.

"About two months previous to the termination of the course, a series of exercises were drawn up for each Class, and circulated among the students. To that individual of each Class who performed the greatest number of these ex

ercises, a silver medal was given; and, from the specimens contained in the Appendix, the Directors will be enabled to judge of the proficiency of the students in this department of science. They will perceive that the time has not been squandered in mere recreation, but in the acquirement of substantial knowledge.

"It would be improper to conclude my Report without adverting to the meritorious conduct of the students. Their attention was often solicited to details of a very dry and uninteresting nature, but no signs of impatience were ever manifested. From all of them I have received the greatest respect; and, from several of them, expressions of kindness and gratitude, which will not soon be effaced from my memory."

There is given in the Appendix, a few of the prize questions given out by Mr. Wilson, with a selection from the solutions that were received. It has been ascertained, to the satisfaction of Mr. Wilson and the Secretary, that these solutions are, bona fide, the productions of the students, and that they received no assistance whatsoever, except such as they could obtain from the books in the library, explanatory of the principles upon which the questions were to be solved.

We select the following questions from this Appendix, as we are sure they must be interesting to our readers, and in the hope that it may stimulate mechanics here, to similar exertions in the acquisition of such useful knowledge.

Exercises of the First Class.

No. I.-The number of teeth in a wheel and pinion, are 260 and 45 respectively; in how many revolutions of the pinion will there be a recurrence of the same teeth?

Answer by ALEXANDER VANNET-Age 24-attended the Third Session. From a consideration of the question, 260

it is evident that

will express the

45 number of times the pinion will revolve during one revolution of the wheel, or that 260 revolutions of the pinion will correspond with 45 revolutions of the wheel. But by reducing the above fraction to its lowest terms, or dividing both numbers by 5, we shall find that 52 revolutions of the pinion, correspond with 9 of the wheel, which will be the fewest revolutions in which a recurrence of the same teeth can take place.

Note. If the numbers (which represent the teeth in the wheel and pinion) have no common measure, or, in other words, are prime to each other, the wheel will have to revolve as many times as there are teeth in the pinion; and, in the same time, the pinion will revolve as many times as there are teeth in the wheel, before there can be a reearrence of the same teeth.

No. VII. A person wishes to construct an orrery, to exhibit the respective revolutions of the earth and moon, supposing the former to turn on her axis 365 times, while the latter revolves 29 times. The pinion will not admit a greater number of teeth than 12; how many teeth must there be in the circumference of the wheel?

Solution by CHARLES GIBB, Mill Wright
Age 18-attended Third Session.

If the number of teeth in the wheel be 365, the number in the pinion must be 29.

But the fraction may be resolved into a continued fraction,

that is, if the pinion has 12 teeth, the wheel must have 151.

No. VIII. -A body plunged into a vessel containing 100 pints of water, loses 12 lbs. weight; how many lbs. of salt must be dissolved in it, in order that the body plunged into the salt water may lose 19 lbs. of its weight. It being supposed that 100 pints of fresh water weigh 60 lbs.-that a body plunged into a fluid loses a part of its weight equal to that of the fluid which it displaces-and also that, when the salt is dissolved, the water is not augmented in bulk.

Solution by JAMES HUTCHISON-Age 16 -attended Third Session-not yet gone to a Trade.

If 60 lbs. (the weight of the 100 pints)

make it lose 12 lbs. of its weight, then to find how many lbs. will make it lose 19, stata 12: 19: 60: 95: ➡the number of lbs. in whole (salt and water). But there were 60 lbs. of water, there must therefore be 95 60, or 35 lbs. of salt.

Mr. Buchanan's Report.

"During the course of Lectures just terminated in the Meshanical Class, in addition to the subjects treated of during the preceding session; the doctrines and the great laws of Motion were also considered; the effects of uniform and accelerated Motion were explained, and applied to calculate the laws of Falling Bodies, and of Bodies descending down Inclined Planes. The same principles enabled us to calculate the descent of rivers, and the motions and discharge of water, either running in an open channel, or propelled in closed pipes by various head pressures. After considering the subject of Clock and Watch-work, and the machinery of the various escapements, and showing those models of the institution which had not been hitherto exhibited, and to which had been added that of the Hydraulic Ram, we concluded with the subject of the Steam Engine, the elementary principles of which the students had already acquired the knowledge of in the course of their studies.

"In the course of the session, several questions were proposed as exercises for the students; the answers to which were in general satisfactory, and showed a complete knowledge of the subjects treated of. To one of these questions which was originally proposed to me by a student, one answer was received from Mr. Joseph Herries, which is so satisfactory, that I have annexed a copy of it as a specimen of the progress of the students,* in the Appendix. It exhibits such a degree of knowledge on the subject of the Strength and Stress of Materials, and of the effect of oblique and of cross strains, as very few Mechanics, at least until the establishment of this Institution, could boast. It has been remarked by Professor ROBISON, when lamenting the ignorance of our Artists on this import ant branch of Mechanics We doubt,'

We regret that we cannot give an idea of this question at present, without a diagram; we may, perhaps, take a future opportunity of doing so.