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towards the end of the present summer, when there would be direct railway communication between cis-alpine and trans-alpine Europe. The Brenner Railway was of high importance, both in a commercial and a political point of v ew. It had no doubt been encouraged by the Austrians, as it would have been of immense value to them when they possessed Venetian Lombarby; and even now, by its passing through the heart of the Tyrol, it was a useful line to them. But it was also looked forward to with interest by the Italians, as being likely to facili tate their commercial relations with Germany and Northern Europe generally. To Great Britain this line was of much consequence, as it opened up a railway communication (via Ostend and Brindisi) with the Mediterranean and the East, independent of France. The Mont Cenis Line, when finished, would be rather the shorter ; but if at any future time political complications unhappily closed that line to English traffic, the Brenner route would be of vital importance ; and even in time of peace, it would be a question whether its little extra length might not be more than compensated for by its better gradients and the absence of the long tunnel. If any members of the Institution connected with Italian railways could obtain detailed particulars of this, the first, and probably the best railway across the Alps, he was sure they would be very acceptable. The atmospheric system of piopulsionhad been alluded to as a means of crossing Alpine Passes. Mr. Pole had had occasion lately to look into the history of this system,* and he would offer a few observations on this application of it. The system had been tried somewhat exten sively some years ago, and had failed to establish itself; but there was a good deal of misapprehension as to the causes of this failure. Many people supposed it was from mechanical defects, and that the whole thing was a delusion. But the facts, as far as he could ascertain them, did not bear out this view. Mr. Robert Stephenson, who was one of the most determined opponents of this system, never called its mecha nical efficiency in question; and Mr. Bidder had declared that he con sidered the mechanical problem as effectually solved. In some of the applications in this country, the system worked the traffic regularly for a considerable time; but the most extensive trial was on the St. Ger main Railway, near Paris, where it worked successfully from 1847 to I860. + The chief reason of the non-success of the atmospheric system where it had been tried, was that it was not suitable, as a system, for general railway traffic. Mr. Stephenson predicted this, but he always admitted that there were exceptional cases where it might be applied with advantage. Such cases appeared to be occurring in the present day ; one might probably be for underground lines, where the use of the ordinary locomotive was objectionable ; and another was on excep tionally steep gradients, such as those necessary in carrying railways over high abrupt mountain passes. Under these latter circumstances, the atmospheric system appeared to offer several most important ad vantages ; as for example— 1. It would allow of the convenient application of any amount of power that might be necessary, and therefore would admit the use of any gradient desired. 2. The great power necessary to drag the locomotive and its supplies of water and fuel up the incline would be saved. 3. The use of a locomotive in such a situation would considerably enhance the dangers otherwise due to the steep inclines and sharp curves; but the atmospheric system would give absolute safety, both in ascending and descending. 4. The atmospheric system would also offer a feasible means of making use of the large water power generally found in such localities. It might be objected that in such inclement situations as the Alpine Passes, the valve of the atmospheric tube would be liable to derange ment; and this objection was doubtless entitled to grave consideration, but he conceived it was not insuperable. Many competent judges were of opinion that in any case a railway at such altitudes must be covered in, if it was to work during the winter season, and if so, this would at once make atmospheric propulsion practicable, either on Val- lance’s plan, or on that heretofore used.J Something had been said as to the use of steel in locomotives. Mr. Pole was inclined to fear that this metal had lately been employed for railway purposes somewhat too hastily and inconsiderately, and he was inclined to hope, from the remarks of Mr. Alexander, that a wholesome re-action was taking place. Mr. Pole had had occasion to watch care- * Vide “Life of Robert Stephenson,” by Jeafferson and Pole, vol. i., chap. xiv. London, 1864. t Vide Perdonnet, “Chemins de Fer,” vol. ii., chap, xi., page 348, 2nd edition, where M. Flachat, the engineer of the line, recommends the use of the atmospheric pressure for inclined planes. He says, “ Le chemin de fer atmosph<$rique de Saint Germain n’a jamais failli .... Jamais un accident ne s’est produit; a securite du service y est absolue ; sa felicite est telle, qu’il me semble mtfriter ce titre 1’attention la plus serieuse des ingdnieurs.” This was in 1860, after nearly fourteen years’ trial. f Since making these remarks, Mr. Pole has had an opportunity of seeing a pamphlet, by Mr. George Edwards (Systeme de Chemin de fer Hydro-pneumatique pour le passage des Hautes Montagnes, Turin, Octobre, 1865), in which the practi cability of working Alpine Passes by atmospheric pressure is fully discussed and warmly advocated. It is not published; but will be found in the library of the Institution. fully great numbers of attempts to substitute steel for iron in armour plates and guns, but these trials had only shown how unfit the metal (at least in its present state of manufacture) was for purposes where it was exposed to sudden shocks and concussions. It was frequently supposed that because steel had greater tenacity than iron, it was there fore proportionately stronger; but this did not necessarily follow, except for strains perfectly quiescent and purely statical. When motion was introduced, and when shocks and concussions took place, simple tenacity was by no means the measure of strength ; for a metal of high tenacity might be very brittle and unyielding, and therefore much less fit to withstand such concussions than a less tenacious material that was softer and more ductile. This seemed to be the case in a large degree with steel, as compared with good iron. In cases where hardness and durability under wear were the principal desiderata, as in tires, no doubt steel was very suitable; but even in these cases much caution was necessary. Instances had occurred, within Mr. Pole’s own knowledge, where steel tires had been broken by the wheels being rather roughly handled in carriage. This was not caused by any fault of the tires (which were made by one of the best houses), but was due to their being shrunk on too tight, which showed, however, how much greater caution was necessary with this material; and that, without such caution, steel might prove -worse than good iron. To guard against this, some of the steel-makers were now producing so soft a quality that it could hardly be distinguished from iron, and in this state its advantages over the more simple and well-known material became problematical. lie could not further yet satisfy himself that the manufacture of steel, under the large production and cheap price at present aimed at, had attained such certainty as to render it trust worthy, in cases where its failure would involve serious consequences. All these matters were well worthy of investigation, and he hoped they would have the careful attention of such members of the Institution as were in a position to obtain information upon them. THE RELATIONS OF GEOLOGY WITH ARCHITECTURE.* Professor Ansted said, I will endeavour to compress into as few words as possible the reply which I have now to make to the various questions which have been put to me, as far as I can collect them and put them into any order on so short a notice. I will begin with one of the last points to which Professor Kerr directed attention, that is, with reference to the value of time in consolidating mortar. It is the universal experience of all persons who have examined old buildings that time does unquestionably produce an amount of harden ing upon mortars and other binding material exposed to it, which no other process can produce. Therefore, whatever the reason may be, we may be sure exposure will improve all cements, which is the main point of that question. There is one other question of Professor Kerr’s with regard to the probable effects of Ransome’s process applied to slate. I do not think it is applicable to slate, or, indeed, to anything but the more absorbent limestones. A very important series of questions occurs with regard to the Lon don stones; but before I proceed to that I will answer the question of Professor Kerr with reference to the help which geology may be ex pected to give to architecture with regard to materials for building purposes, and this will afford me an opportunity of mentioning why the grits are not used in London. The first reason would be, because all the grits of any importance that would be used for domestic archi tecture, except for the most expensive buildings, are out of the ques tion on account of cost. You see at any rate, then, that I do not ignore this question of cost, which, on the contrary, I have been in the habit of regarding as a very important one. No doubt many of the sand stones, especially those of Yorkshire, and most especially those of Scotland, are, as building materials, exceedingly to be preferred, so far as durability is concerned, to many other kinds of stone. Speaking, not as an architect but from general knowledge, I may say, that one very good reason why this stone would not be employed largely in stone buildings is that it is not adapted for those artistic decorations which are generally preferred in domestic and church architecture. Sand stones only lend themselves to large forms of decoration, and thus when sandstone is used and an attempt is made to work it into delicate ornamentation, it is likely to fail. Thus it is not only expensive to pro cure, but the ornamented parts constructed of it are liable to injury from exposure. All the stratified grits are more or less absorbent in the planes of stratification, and when moisture gets in they scale when the first frost attacks them. Many sandstones that will stand exposure in the block will fail when badly placed. Others, however, are very durable and exceedingly compact. Limestones are, no doubt, used because they are so easily to be had at a moderate distance from London. We are not situated near any good sandstones, and our buildings naturally take the complexion of the surrounding country. Till a recent period we have had no rail ways to carry stone, and I need not point out that even now to convey * Concluded from page 79 ante.