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debted to Mr. Mallett. The object of former tabulated results was to determine the actual loss by corrosion in a given time, and the comparative durabilites of rust of the principal “ makes” of cast iron of Great Britain, and to discover on what durability depended. The tables of experiments now presented show, that the rate of corrosion is a decreasing one in most cases ; and that the rapidity of the corrosion in cast iron is not so much dependent upon the chemical constitution of the metal as upon its state of crystalline arrangement, and the condition of its constituent carbon. The present report, too, extends the inquiry to wrought iron and steel, of which between thirty and forty varieties have been submitted to experiment. The results show that, the rate of corrosion of wrought iron is in general much more rapid than that of cast iron or of steel. The finer the wrought iron is, and the more perfectly uniform in texture, the slower and the more uniform is its corrosion. Steel corrodes in general more slowly, and much more uniformly, than wrought or cast iron. The results of the action of air and water in the several classes of iron have been examined and chemically determined. The substance spoken of as plumbago was next described. It is produced by the action of air and water on cast steel, especially that in the raw ingot, in the same way as it is in the case of cast iron. A quantity of plumbago, found in the wreck of the “Royal George,” absorbed oxygen on exposure to the air with such rapidity that it became nearly red hot. Mr. Mallet next described a method of protecting iron by a modification of the zinc process. It was found impossible to cover the surface of iron with zinc, to which it had no affinity. The first process was to clean the surface of the iron, taking off the coat of oxide, and then immersing it in double chloride of zinc and ammonium, which covered it with a thin film of hydrogen, by which its affinity for the zinc is much increased. The iron was then covered with a triple alloy of zinc, sodium, and mercury. Mr. Mallet produced several specimens of his alloy, one of a bolt to be driven into a ship's side, and another a cannon shot covered with his preparation, and exposed to the weather on the roof of a building, and which was perfectly preserved. Cannon balls were so much oxidized by exposure to atmospheric influences that in five or six years they become useless. The French Institute had been engaged in experiments to protect these, and had tried zinc, but had been compelled to abandon it. Mr. Mallet also brought under the notice of the Section a method of preventing the fouling which takes on the bottoms of iron ships, especially in tropical climates, by means of which invention he had ascertained that plants and animals were prevented from adhering to the ship's bottom. According to Mr. Nasmyth's theory, corrosion on railways is checked by the trains passing in one direction, and takes place when they pass in both directions. Mr. Mallet had made some experiments in order to determine this point, which were not yet complete; but he was inclined to think that the difference between the two cases were apparent and not real. He

was continuing his investigations, and hoped to report further on a future occasion.

Dr. Schunk read a paper “ On Hæmatoxylin, the Colouring Principle of Logwood," by Prof. O. L. Erdman, of Leipsic.—The Hæmatoxylin used by the author in his experiments was prepared by the process of charcoal. In a state of purity, hæmatoxylin is not red; it is in itself no colouring matter, being merely a substance capable of producing colouring matters in a manner similar to lecanorin, orcein, or phloridzin. The colours which it produces are formed by the simultaneous action of bases (particularly strong alkalies), and of the oxygen of the atmosphere. By the action of these it undergoes a process of eremacausis, which, after forming colouring matters, ends in the production of a brown substance resembling mould. The colour of hæmatoxylin varies from a pale reddishyellow to a pale honey colour. The crystals are transparent, possess a strong lustre, and may be obtained a few lines in length. Their form is a rectangular four-sided prism, sometimes with a pyramidal summit. The taste of hæmatoxylin is similar to that of liquorice. With excess of ammonia, it forms what the author calls hæmatein, analogous to orcein, &c.

“On an Economical Voltaic Combination of extraordinary power," by F. W. de Moleyns, Esq. The author stated that, while the discoveries in electro-magnetism gave promise of its ultimate application as a motive power far surpassing steam, it was matter of much importance to discover a mode of charging or giving attractive power to soft iron, at a cost which should render it as a mechanical agent generally available. The voltaic arrangement now produced to the Section, the author believed would be found to possess in a very great degree those advantages so much desired for the proper developement of electro-magnetic energy. The combination consisted of an acidulated solution of nitrate of ammonia, in contact with platina, solution of muriate of ammonia, and zinc; the nitrate solution being separated from the muriate by a diaphragm of wood, biscuit-ware, or other porous substance not acted upon by the liquids. The acidulated solution was thus prepared : six ounces of nitrate of ammonia are dissolved in two fluid ounces of soft water, and this solution is then combined with an equal quantity, by measure, of the pure sulphuric acid of commerce, adding the acid gradually, the vessel containing the mixture being kept in a frigorific preparation, so as to prevent the heat evolved exceeding 100 degrees. The muriate of ammonia is dissolved in soft water to saturation. The zinc is not amalgamated, and the use of cast zinc is to be avoided. The platina is the thinnest foil that can be procured, but the author found that box-wood cut to the thickness of veneer, and charred on each side superficially, might be substituted, and used with equal advantage. The author stated that, with a voltaic, combination consisting of half a fluid ounce of the acidulated nitrate solution, one ounce of the saturated solution of the muriate of ammonia, a strip of platina foil three inches by two, surrounded by a piece of sheet zinc of equal surface, he had succeeded in supporting a weight of 2,000 lb. with an electro-magnet of the horse-shoe form, measuring sixteen inches from pole to pole, and three-fourths of an inch in diameter, and that the attractive force, before contact, was in proportion.

“On a Peculiar Condition of Iron," by Prof. Schöenbein.”—In this paper the learned author continued his researches upon the different effects produced by iron in its active and passive states. Without a detailed description of the apparatus employed in the production of the singular phenomena observed by the Professor, and which our space will not permit us to give, it is impossible to make the phenomena themselves intelligible. They are intimately connected with the curious fact, discovered by the author, of the property which iron possesses with respect to oxygen, i.e. in certain conditions to be an oxidable, in others a non-oxidable metal.

“On a new method of Analyzing Cast Iron and other Metallic Carburets,” by Dr. Ure.--The method proposed by Dr. Ure is similar to that of Regnault and Dr. Bromeis, with the exception that he employs pure chlorate of potash in the combustion, instead of a mixture of that salt with chromate of lead, and collects the resulting carbonic acid in a peculiar pneumatic apparatus, filled with diacetate of lead, instead of the potash apparatus of lead.

“On the Composition and Characters of Caryophylin," by Dr. Lyon Playfair.—The author pointed out the most advantageous method for obtaining caryophyllin. He mentioned that only a small quantity could be derived from cloves by a direct process; but that, by a protracted digestion with alcohol and the exposure to the air, a considerable quantity might be procured from Caryophyllus aromaticus. Dumas and Ethling had assigned the formula C, H, O, to this substance. Dr. Playfair stated, that although this is the correct expression of the composition of melted caryophyllin, it is not so of the substance in its natural state. He found the empirical formula of caryophyllin dried for several days at 212°, to be C40 H 33 Os, or the rational formula C40 Hz, 04X HO. A considerable heat is required to expel this water in the open air, but it escapes at a moderate heat in vacuo.

Sir J. Robinson explained Mr. Prosser's method of making earthenware or porcelain from dry powder or clay compressed. The advantage was that no twisting or alteration of shape (excepting a little shrinkage) took place in the burning. From the accuracy with which articles formed by compression retained the shape of the mould, they could be fitted together very easily and smoothly. Sir J. Robinson showed a piece of tesselated pavement made of these tiles, which, although just laid together without cement, was perfectly smooth on the surface. He wished particularly to introduce to their notice a roofing tile of construction novel in this country: from the peculiar manner in which these tiles overstepped

each other, a little Roman cement rendered them perfectly watertight; and from their not being absorbent, they were not liable to exfoliate, and would, therefore, be almost imperishable. The old form of tile weighed about 105lb. per square yard, while this only weighed 581b. They were manufactured at Stoke-upon-Trent.

Mr. J. S. Russell explained his “ Indicator of Speed of Steam Vessels." This was a simple application of a well known principle; it was not novel, but he had applied it successfully, although others had failed. It depended on the hydrodynamical fact, that if a reservoir be filled with water to a certain height, the water will flow from an orifice at the bottom with a velocity proportionate to the height; and conversely, if the reservoir be empty and this orifice turned towards stream, the water will rise in the reservoir proportionate to the velocity. His plan was to pass a tube through the bow of the vessel, and carry it along the flooring to the centre of gravity of the vessel, where it terminated in a vertical glass tube, exhibiting the weight of water within. To this tube there was attached a moveable scale, the zero of which being placed on a level with the point at which the water stood when the vessel was at rest, the rise of the water in the tube when the vessel was set in motion exhibited the velocity at which the vessel was passing through the water. He had tested the accuracy of this indicator by sailing vessels at least twenty times over a measured distance of 15 miles, and comparing his tube with Massey's log, the common log, calculations from the number of strokes, &c., he found it more accurate than any. By putting a stopcock in the pipe just under the glass tube, he was enabled to regulate the orifice until the greatest regularity was obtained, and he could now depend on the indications within the twentieth of a mile. From these experiments he had constructed a scale, which he exhibited, and of which the following is an extract; the first column exhibiting the speed in miles per hour, and the second the height of the water in the tube above the zero line, expressed in feet :Miles per hour.

Feet on the scale.
15 ....

7.5625
5.6800
4.067
2.722
1.647
0.84

0.3025
1......

0.0336 Prof. Vignoles read a communication “On the use of Béton and Concrete in the construction of Breakwaters.” The use of béton had greatly increased in France of late, especially in marine works ; it was similar to concrete, but not exactly identical with it. Béton, like concrete, was composed of lime mixed with broken stones, gravel and sand; but it was supposed to require hydraulic lime,

13 ....

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while concrete in this country was frequently made of common lime when not to be exposed to the action of the sea. Béton was first introduced in France by Belidor, and lately much advocated by Vicat; since then it had been much used, and he considered that attention was due to the use that had lately been made of it in the Port of Algiers by M. Poiteul, the engineer of that harbour.

Mr. P. Taylor had witnessed the complete success of this system at Marseilles, where a very difficult structure had been accomplished in this way The original béton was a cement made of lime and ground brick; this made a very good cement; cubic masses of this concrete, 10 feet on the face, were used. These cubic masses were formed at Marseilles on the very brink of the precipice over which they were to be rolled into the sea. He was now constructing four bridges, and he was as confident in placing his foundation on béton as on stone, he had so often witnessed the efficacy of the plan-one point was that in France they had very good hydraulic lime.—Mr. Thompson said, that when good hydraulic lime was not to be procured, he had used the chalk lime of the north of Ireland, which, though useless by itself, afforded a good cement when mixed with clay. The lime was burned and ground, the clay was ground and well mixed with the lime; this was then burned in a kiln, and the mortar was quite satisfactory, but too expensive for common use.—Mr. Smith (of Deanston) had lately directed his attention to the same subject. Concrete might also be used to make tiles for drying land when clay was dear and fuel was expensive ; hollow tubes of concrete might be made in the drains by using proper cores, and constructing them in lengths of 3 or 4 feet, pouring the concrete round the core, leaving small apertures for the admission of water. He considered that they might be made on a larger scale, so as to be very serviceable for sewers. Mr. Bateman had been compelled to resort to artificial lime for a large water work in Ireland; he tried M. Vicat's experiments over again, and found that they succeeded perfectly in experiment, and even on the large scale while the pressure of water was moderate, but when the depth reached twelve feet, he found the lime was completely washed away where unsupported, and even the floor of the culvert was at length disintegrated by the action and pressure of the water: from this he concluded that Vicat's experiments should not be implicitly trusted in great pressures of water.—Sir M. I. Brunel explained the great cohesion of bricks, when interlaid with hoop iron or laths beaten into a fibrous state.

Mr. L. Schwabe explained his method of spinning glass, and brought forward specimens of the glass thread, and also of the cloth woven ; he showed the spinning machine with which this was effected, and also displayed many other filamentous substances from which he had succeeded in fabricating cloths, Assam silk, fibres of the pinna, &c.—Sir J. Robison mentioned that the strength of this silk in proportion to its lightness, was such that Mr. J. S. Russel

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