THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[JVVK, 



portion of the wall. This plate or layer should be a little above the inter- 

 oal level of the fouodatioDS. 



This method, however, though efficacious in resisting the dampness aris- 

 ing from the ground, does not prevent the efTects which the humidity of the 

 atmosphere produces on the exterior surface of the walls in their lower 

 part. In ordinary buildings we may point out as an excellent preservative 

 against atmospheric moisture, a rev^teraent of flag stones placed against the 

 external face of the wall, and reaching to about a yard above the ground. 

 If the fonndations of the walls be of good limestone or grit-stone, this re- 

 v^tement will not be necessary. It is well known that in the lower parts of 

 walls to a certain height above the ground, the mortar of hydraulic lime 

 should alone be used, and that when there are means of resting the found- 

 ations on an impermeable concrete, the best effects may be anticipated. 



The precautions, then, to be taken against humidity in the walls are 

 these— a foundation on hydraulic cement, the employment of hydraulic 

 mortar in the lower parts of the building, the use of calcareous stones or 

 refitement built against the walls, and the interposition of an impermeable 

 substance through the whole thickness of the walls between the exterior 

 and interior levels of the soil. 



ATMOSPHERIC RAILWAY. 



Sir — 1 think your correspondent S. T. is labouring under a mistake 

 when he epeaks of monthly attacks on the atmospheric system. The com- 

 parison of theory and experiment shows that the development of the latent 

 heat of air, during its sudden compression in the pump, causes a small and 

 unimportant loss when the degree of rarefaction does not exceed the limits 

 assigned by the patentees. 



The losi by leakage depends on the degree of perfection in the machinery, 

 and remains to be determined by experiment. 



The regularity with which the Dalkey line has acted during the past 

 jear, as well as the high velocities attained on the Croydou line, are very 

 satisfactory. The failings of the engines and pumps in the latter case have 

 been frequent, but few will be inclined to doubt the possibility of surmount- 

 ing this diOScuIty. After examining all the tables and writings that I can 

 find respecting the practical working of a very defective example, I can 

 see no good reason to doubt the capabilities of the system. One fair trial 

 of the constancy of the system will be of more value than volumes %vritten 

 on the subject. In the mean time it is very desirable that the opponents of 

 the system, should patiently await the result of the experiment that is now 

 being made, for they may rest assured that the case will be decided on its 

 own merits, and (juite irrespectively of their assertions. In the mean time it 

 will be remembered that the losses inherent in the system are very trifling 



A few years ago it was believed that the adhesion of the driving wheels 

 of a locomotive to the rail was insufficient to enable it to draw its load and 

 Dumerous walking machines were patented. A simple trial would have 

 saved much time and money. It will be better to test the constancy of the 

 atmospheric system rather than trust to doubts and surmises. 



It has lately been asserted that the power of the locomotive is nearly 

 double of the Croydon atmospheric. However, if the greatest evaporating 

 power of any locomotive engine hitherto constructed be combined with any 

 cylinder and driving wheels, in actual use, I think it will be found that at 

 velocities of GU to 70 miles per hour, the efficient power of locomotives 

 falls couiiiderably below that of the Croydon Atmospheric. 

 I remain, Sir, 



Your obedient servant, 



F. Basbfortii. 



Semper has been chosen architect of the new Picture Gallery at Dres- 

 fled. At Berlin, the king has ordered the erection of a vast cathedral ; 

 the spires are to be 300 feet high. The new Campo Santo, which will be 

 connected with the cathedral and palace by a collonade, will be a large 

 open square, of whicli the sidts will be 180 feet long. There will be a 

 covered arcade or ambulatory all round the square ; and the inner walls 

 •f this arcade will be covered with frescoes from the designs of Cornelius. 



PBOCEEDINGS OF SCIENTIFIC SOCIETIES. 



ROYAL INSTITUTE OF BRITISH ARCHITECTS. 

 May 11.— Mb. Tite, V.P., in^the Chair. 

 Mr. Scoles, honorary secretary, read a letter from Mr. Myers, dated Rome, 

 contradicting the reports which were current a abort time ago, that the 

 dome of St. I'eter's was in danger. Some repairs had been made last sum* 

 mer, one or two of the string courses bad been restored, and this had pro- 

 bably given rise to the assertion. A contradiction of the report appeared 

 immediately after the statement was made. With reference to the fact that 

 there had long been numerous cracks in the dome, the chairman reminded 

 the meeting of an anecdote, respecting some figures erected in the cathedral, 

 the architect, on being asked his opinion of them, said there was too mnch 

 flutter in the drapery. " That ;" replied the sculptor, " is caused by the 

 wind through the cracks you have made in the dome."' 



A paper by M. De Lassaux, on a preparation of plaster of Paris, proposed 

 to be used in England as an improvement on that now sold. In France, 

 plaster is employed extensively for external work, and endures well ; whereas 

 that in England will not stand the weather. The buildings in the Champt 

 Elyse'es, erected on lease for forty years, are mainly constructed of plaster. 

 The Circus there, a model in its way, is chiefly of iron and plaster. The 

 English plaster-stone might be called a sulphate of lime; and he considered 

 it was the presence of a small quantity of sulphuric acid in the plaster 

 which prevented its endurance. The plaster, for which he had established 

 a depot in England, might be used externally, as in France ; and, moreover, 

 was very moderate in cost, being 30s. per ton. As a guide, the paper stated, 

 twenty-six pounds of the plaster, costing 4 Jd., would cover one yard of wall ; 

 and thirty-two pounds, the cost of which would be i^i., a yard of ceiling. 



Mr. Bellamy observed that the price at which it was stated in the fore- 

 going paper that the plaster could be supplied, was most materially lower 

 than that of English plaster. He wished, however, to know whether the 

 price mentioned included the import duty. The present cost of plaster ia 

 England was 3/. 10s. per ton for the coarse, and H. hs. for the fine; so that 

 the difference between this and the plaster introduced by M. de Lassaux was 

 very great. 



M. De Lassadx replied, In French, that there was no duty on plaster im- 

 ported into England. He alluded also to the valuable property of this plas- 

 ter when used as a coating to iron, of preventing oxidation. The plaster 

 was thoroughly dried in eight days. 



Mr. Tite remarked on the very extensive use of plaster for external deco- 

 ration in Paris, \fhich was a principal cause of the difference between the 

 appearance of the streets of that city and those of London. A great diffi- 

 culty in introducing cement into general use here was its shrinking in the 

 drying, and this difficulty was especially felt when the material was employed 

 for " pointing," or filling crevices. .Umost every kind of cement, except 

 plaster of Paris, diminished in bulk in setting, and consequently was apt to 

 fall out when used in pointing. Plaster of Paris, however, expanded in set- 

 ting : it probably contained a portion of carbonate of iron as well as sulphate 

 of iron. A remarkable illustration of this property of expansion was afford- 

 ed by the method in which party-walls were usually built in Paris. They 

 were never connected with the external walls, as in this country, but were 

 separated from them by a considerable interval. The reason of this was, 

 that the party-walls being built of rubble, it was necessary to make consider- 

 able allowance for their expansion in drying. When used for external 

 mouldings, it was usual in Paris lo protect the upper surface of the plaster, 

 which was most exposed to the weather, with thin plates of zinc. 



Mr. PovNTER thought that the great difference between the climates of 

 London and Paris must have a great effect on the durability of these mould- 

 ings when used externally. Wooden blinds which, when exposed to the air, 

 would not last more than a few years in London, would in Paris remaia 

 sound almost as long as the houses themselves. Canvass blinds, in England, 

 generally perished in two or three years. He considered that this rapid 

 decay was owing not so much lo the actual quantity of rain which fell in a 

 year, as to the general humidity of the atmosphere. This was particularly 

 observable in the vine, a plant which, it was well known, endured a degree 

 of cold far more intense than it was ever subjected to in England, and yet 

 never flourished in this climate on account of its constant moisture. 



Mr. Bellamy remarked that he had observed, in Nottinghamshire, two 

 instances of houses being thrown down from space not having been left for 

 the expansion of the party-walls when built with plaster. 



Mr. Tite did not think the humidity of the air here was a sufficient cause 

 for the explanation of the rapid decay of plaster. The climates of some 

 parts of Switzerland and Bavaria were fully as humid as our own, and yet 

 these effects were not observable there. At Freiburg, for instance, block 

 tin was very much used externally without decaying or becoming tarnished- 

 The angles of the spires of churches were frequently covered with sheets o£ 

 tin, which, when the sun shone on it, looked as bright as silver. In the 

 same way, tin was used for the heads of water pipes and other purposes 

 with equally good effect. In Canada, also, the same thing was observable, 

 and it could hardly be disputed that the climate of many parts both of Ca- 

 nada and Switzerland was quite as damp as that of London. He thought 

 there must be anotlier agent at work to produce the destructive effect alluded 

 to ; he was, however, unable to indicate the true cause. It was well knowa 



