tion. The Rev. Prof. Chevallier asked, whether it was not necessary to vary the dimensions of the several curves of a vessel built on his principles to suit the velocity with which she was intended to move.-Mr. Russell answered that it was necessary.—Sir John Herschel was anxious that Mr. Russell should describe minutely to the section the manner in which his experimental waves were generated; before, however, he gave Mr. Russell the opportunity of doing so, by resuming his chair, he would state the reason why he was anxious on this point. Prof. Weber, as Mr. Russell had informed the section, had some time since traced with much accuracy the motions of the several particles of the fluid mass during the transit of a wave, and had assigned the circular motion of each near the top, and the elliptic motions varying as you approached the bottom; but from his researches it would appear that each particle during the transit of a wave described the full circuit of its own curve, so as to return, as soon as the transit of the wave was completed, to the spot from which it had started when its equilibrium was first disturbed on the approach of the wave; whereas, if he understood Mr. Russell rightly, he had described cases in which the particles only described semi-curves, beginning with the semi-circle at the surface of the fluid; and did not describe the under-half of their curves, so as to return to the places from which they had started at the commencement of their motions. If he had apprehended this rightly, it furnished a case in the propagation of undulations in water very analogous in its physical circumstances to the loss of a half-wave of light at the change from refraction to reflexion, and might perhaps lead to some conception of the origin of the distinction between positive and negative polarization in the luminous waves.-Mr. Russell said that he would describe the manner in which he generated the waves in his experimental canal, by which it would appear that he could at pleasure produce either a positive wave, or that which consisted of an elevated ridge only passing along the surface of the canal, or a negative wave consisting of a depression alone, similarly progressing, or a wave compounded of a positive and a negative wave, or one in which there was a ridge accompanied by a depression to constitute the wave. By penning up an elevated column of water at one end of his experimental canal, which was separated from the rest of the fluid by a sluice or diaphragm placed across it, when he suddenly opened this sluice the positive wave was generated; by depressing cautiously into the end of the canal a mass of foreign matter, as, for instance, a block of wood, a positive wave was also generated; by slowly and cautiously

drawing out the same block the negative wave was generated; and by letting fall a considerable body of water from some height above the surface at one end of the canal, a compound wave was generated. During the transit of a positive wave each molecule of the fluid only passed through the upper half of its semi-curve, and thus only passed forward by the length of its longer axis without returning to its place; during the transit of a negative wave each molecule described only the lower portion of its curve, and thus went backward by the length of its axis, without returning again to the place from which it had been disturbed, while, during the transit of a compound wave, each molecule of the fluid described both the upper and under portion of its own curve, and thus returned at the conclusion of its transit to the place from which it had begun its motion when first disturbed.

Mr. Robert Mallet read his report of the experiments, instituted at the command and with the funds of the Association, "On the Action of Sea and River Water, whether clear or foul, and at various temperatures, upon Iron, both cast and wrought," by himself and Prof. E. Davy, of Dublin.

This subject is one of great interest to the engineer, as well as the chemist, as the former has no knowledge of the rate of action, relative or absolute, of water on iron under various conditions; and the chemist does not know precisely the changes which ensue during this action. The report is comprised under four principal sections, viz. :-First, a brief "précis" of the actual state of our chemical knowledge of the subject, i. e. of the reactions of air and water on iron. This embraces the following subdivisions of the subject: A. of the action of pure water free from air on iron, at various temperatures, and the nature of the compounds formed, which are at low temperatures, (Fc O) +

2 3

ment of the nature and extent of the experiments, which have been made on the great scale for the use of the engineer, as well as chemist, on the action of water on iron; for this purpose, boxes containing regularly formed specimens of nearly all the makes of iron in Britain, have been sunk,-1. in the clear water of Kingstown Harbour; 2. in the foul water of the same; 3. in foul river Liffey water; 4. in clear water of the same; and 5. in sea water maintained constantly at a temperature of 125° Fah. These will be examined twice a year for four years, and will give the relative and absolute rates of corrosion of the included specimens, which are contained in boxes so contrived as to allow free access of air and water to them. The third section contains a refutation of the method proposed by Mr. John B. Hartley, at Liverpool, for preserving iron by brass, which is shown by numerous and careful experiments, chiefly by Prof. Davy, and by appeal to the results of actual use, as well as the results of Schoenbein and other continental philosophers, to be wholly erroneous, and contrary to all theory, and to be productive of a most rapidly increased corrosive action of water upon iron when present. Fourthly, a new method, founded on electro-chemical agencies, is proposed for the protection of wrought and cast iron, now in progress of experiment; and, lastly, the report concludes with the statement of various desiderata upon this subject. All the details of the subject, such as the action of sea water in converting iron into a plumbaginous material, and the nature and properties, &c. of this subject, are necessarily omitted in a mere abstract.

"On the Construction of Apparatus for solidifying Carbonic Acid, and on the elastic force of Carbonic Acid Gas in contact with the liquid form of the Acid, at different Temperatures," by Mr. Robert Addams.

Mr. Addams prefaced the communication by adverting to the original production of liquid carbonic acid by Dr. Faraday, in 1823, and also to the solidification of the acid by M. Thilorier, and then exhibited three kinds of instruments which he (Mr. Addams) had employed for the reduction of the gas into the liquid and solid forms. The first mode was mechanical, in which powerful hydraulic pumps were used to force gas from one vessel into a second, by filling the first with water, saline solutions, oil, or mercury; and in this apparatus a gauge of observation" was attached, in order to see when the vessel was filled. The second kind of apparatus is a modification of that invented and used by Thilorier. The third includes the mechanical and the chemical methods, and by which, as stated, a saving of a large

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quantity of acid formed in the generator is effected; whereas by the arrangement of Thilorier's plan, two parts in three are suffered to rush into the atmosphere, and are lost. With this set of instruments are used two gauges of observation-one to show when the generator is filled with water by the pumps, and consequently all the free carbonic acid forced into the receiver; and the other to determine the quantity of liquid acid in the receiver. He likewise exhibited other instruments for drawing off and distilling liquid carbonic acid from one vessel into another, and mentioned some experiments which were in progress, and especially the action of potassium in liquid carbonic acid, -an action which indicated no decomposition of the real acid, but such as implied the presence of water or a hydrous acid. A table of the elastic force or tension of the gas over the liquid carbonic acid, was shown, for each ten degrees of the thermometer, beginning at zero, and terminating with 150 degrees. The following are some of the results:

Mr. Addams announced his intention of examining the pressure, at higher temperatures, up to that of boiling water, and above; and asserted his belief that it may be profitably employed as an agent of motion-a substitute for steam-not directly, as had been already tried by Mr. Brunel, but indirectly, and as a means to circulate or reciprocate other fluids. The solidification of the acid was shown, and the freezing of pounds of mercury in a few minutes, by the cooling influence which the solid acid exercises in passing again to the gaseous state.

"An Improved method of Constructing Railways," by J. Price.

This method consists in fixing rails on a continuous stone base, a groove having been made in the stone to receive a flange or projection of the lower side of the rail. The stones and rails are to break joint with each other, and the chair by which the rails are to be secured is to be made fast to the rail by a bolt, not rivetted, but slipped in. The chair is to be sunk until the top is level with the top of the stone, and fastened to it by two small wooden pins. Any sinking of the road is to be obviated by driving wedges of wood underneath the stone until it is raised

to the required height. The chairs are to be fixed at about 4 feet apart, and to weigh, if of malleable iron, 14 lbs., but if of cast iron 20 lbs. the rail to weigh 50 lbs. per yard.

"On the Construction of a Railway with Cast-iron Sleepers, as a substitute for Stone Blocks, and with continuous Timber Bearing," by T. Motley.

The cast-iron sleepers, which are wedgeshaped, and hollow, having all their sides inclined inwards towards the under side, are to be laid transversely, and the timber is to pass longitudinally through the centre, and to be secured by wedges of iron and wood. The sleepers are to be six inches apart, and the timber of such a thickness as to prevent any perceptible deflexion betwixt the rails. The road is to be ballasted up to the top of the sleeper, and the timber to stand out sufficiently, and to have any approved rail laid upon it.

Mr. Stephenson considered the plan too expensive. Mr. Donkin observed, that a certain portion of elasticity was beneficial.

"Machine for raising Water by an Hydraulic Belt," by Mr. Hall.

In this machine an endless double woollen band, passing over a roller at the surface of the earth, or at the level to which the water is to be raised, and under a roller at the lower level, or in the water, is driven with a velocity of not less than 1000 feet per minute. The water contained betwixt the two surfaces of the band is carried up on one side and discharged at the top roller by the pressure of the band on the roller, and by centrifugal force. This method has been in practice for some time in raising water from a well 140 feet deep in Portman Market, and produces an effect equal to 75 per cent. of the power expended, which is 15 per cent. above that of ordinary pumps. This method would be exceedingly convenient in deep sha'ts, as the only limit is the length of the band, and many different lifts may be provided.

Mr. Hawkins had seen a machine very similar, fifty years ago.-Mr. Donkin, without entering on the question of originality, stated that he had seen a machine of this description working with a beneficial effect of 75 per cent., the beneficial effect of ordinary pumps being about 60 per cent.

"On Clegg's Dry Gas-Meter," by Mr. Samuda.

of heat to one of the globes will cause the alcohol to rise into the other. The pulse glass is fixed on an axis, having a balance weight projected from it, and the axis works in bearings on the sides of a chamber through which the gas to be measured is made to passin two currents, one of which is heated and the other cold. The hot gas is made to enter opposite to, and to blow upon the lower globe of the pulse glass, while the cold gas blows upon the other. The difference of temperature thus established between the globes causes the alechol to rise into the upper one, and the glass turns over on its axis, thus varying its position, and bringing the full globe opposite to the hot stream of gas. This stream, with the assistance of the cold gas, which condenses the vapour in the top globe, repeats the operation, and the speed at which the globes oscillate will be precisely in proportion to the quantity of gas which has been blown upon them, provided a uniform difference of temperature is always maintained between the two streams of gas. The difference of temperature is established and rendered uniform by a small flame of gas, which heats a chamber through which the lower current of gas has to pass, and the arrangements for securing an equality in the difference of temperature are very ingenious. The instrument is first tested by making a given quantity of gas pass through it, and observing the number of oscillations of the pulse glass. This once established, the instrument registers the quantity passed with inconceivable accuracy.

Considerable discussion ensued, during which many objections were raised, to which Mr. Samuda replied.—Mr. Liddell observed, during the progress of the discussion, that a flame consuming one-fifth of a cubic foot of gas per hour would burn in a chamber, and not be liable to be extinguished by the opening and shutting of doors; and that if due precaution were used, a flame might be preserved with a consumption only of one-eighth or one-tenth of a foot per hour.

"On the construction of Geological Models," by Thomas Sopwith.

Mr. Sopwith lays down a method by which the commonest workman can make geological models, showing not only the position and thickness of the strata in a vertical section, but the actual surfaces and imbedding of the strata lying in different planes; so that one tray of the model being taken from above the other, we may consider that we have the stratum in miniature, with every undulation and indentation upon it. There was exhibited a model of the Forest of Dean, constructed in the follow

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After

divided by lines crossing each other at right angles, and at the distance of a mile from each other. A vertical section was then prepared corresponding with each of these lines. These sections were drawn upon thin pieces of wood in the ordinary manner of a vertical geological section, and the several pieces of wood were then united by being half-lapped together, forming a skeleton model of vertical sections. After being thus united, the several sections were taken separately, and cut into as many portions as were required to illustrate the successive layers of strata; the intersection of each of these portions having been first marked by a number at the several corners. each section has been divided into its several parts, these respective portions are again united, and formed the exterior boundary of a square mile of rocks. The interior of this is filled with wood, and carved so as to coincide with the sections. Any intermediate portion can be fitted in with great exactness, first by a thin or skeleton section, and afterwards by wood, which any workman can carve with the most exact accuracy as quickly and as surely as any ordinary mechanical operation; and thus at once a connexion between the most complicated section and the art of a common workman is accomplished. The outline of the surface, and the general contour of the country, is obtained, partly by means of the skeleton sections, and partly by the use of a gauge, or graduated pencil, sliding in a frame, in the same manner as practised by sculptors in transferring the dimensions of a cast to a block of marble.

(To be continued.)

NOTES AND NOTICES.

Davies's Fire-proof Composition.-Sir,-Among the list of patents given in your 786th Number (p. 383), there is a notice of one granted to "Joseph Davies, of Nelson-square, Blackfriars-road, Gentleman, for a composition for protecting wood from flame." I feel myself called upon to state, that it was this composition which formed the subject of the highly interesting experiment in Dorset-street, Claphamroad, detailed at page 233 of your 778th Number, in which I erroneously described it as De Witte's fire-preventive composition. Mr. De Witte being associated with Mr. Davies, and having taken an active part in the several public and private trials that have been made with this patent composition, some other writers besides myself have been led into a slight mistake, which I take this opportunity of correcting. In an affair so truly humane, and of

such national importance, it is necessary that the public generally, and the scientific world in parti cular, should be rightly informed, both as to the invention and its inventor; the former has been repeatedly demonstrated to be worthy of universal adoption-the latter is, consequently, deserving of public gratitude. I remain, &c. WM. BADDELEY.

London, Sept. 7, 1838.

Belgian Railroads.-In the course of last month the number of passengers on the Belgian railroads was 269,086; the receipts amounted to 409,679 franes 80 cent. There is no other instance of such a result. It is, therefore, very unjustly that the establishment of iron railroads has lately been looked on in a more unfavourable light, on account of some accidents, which are of very trifling importance, relatively to the number of persons who have travelled by these roads. We have received the following letter on the subject from Aix-la-Chapelle :-" The accidents which have lately taken place on the Belgian railroads, and which, as usual, have been amplified, in proportion to the distance that the news has travelled, since the two persons killed have been multiplied to 200 by the time the news reached Prussia, do great injury to the shares in the iron railroads from Cologne to Elberfield. The public fearing the prejudices that may ensue, the shares have fallen to 92. The directors wishing to obtain all possible information on so important a subject, and to profit by any useful advice proceeding from other persons, have caused letter-boxes to be put up in the principal towns, through which any person may communicate his ideas anonymously."

The Great Western.-The success which has attended the steam navigation to America, and the preference given to it, exceed all expectation. It appears that before the arrival of the Great Western from New York, all her berths amounting to 130, were engaged for the return voyage fixed for the 8th instant. So numerons were the applications, and of course the number disappointed, that premiums of 20 guineas have been offered, and would be given, for berths on the first refusal of vacancies from parties who by any accident might be prevented from going. In an instance a party having engaged a double berth, was written to in Devonshire to request accommodation for a passenger, if the whole were not absolutely wanted. The directors have fitted up every yard of disposable space on deck, as well as below, in order to make room for the number stated. Upon the 87 passengers home, and the 130 out, at 40 guineas passage money per head in saloon, and 35 guineas cabin, each way, the directors of the Great Western will have received, therefore, upwards ol 8,0007. exclusive of the benefit derived from the conveyance of goods, of which the Great Western brought from New York to the extent of about 200 tons measurement.

Taylor's patent Propeller.-We have received a letter from Mr. Lowe, of King-street, Old Kentroad, (for which we have not room this week) claiming the invention of the propeller described in our last Number, p. 400, as his, and stating that it was surreptitiously obtained from him by Mr. Taylor. Mr. Lowes states, however, that his patent was sealed in March last, two months prior to Mr. Taylor's: his right is therefore secure as against all subsequent patentees.

The Railway Map of England and Wales continues on sale, in a neat wrapper, price 6d. ; and on fine paper, coloured, price is.