MECHANICAL AND USEFUL ARTS. 9D 



obliged to go to another quarry in the same neighbourhood, which was not of the 

 same quality of stone as that which had been experimented upon by the Com- 

 missioners, and no doubt this is the correct history of the matter. 



With respect to the sound condition of the carved stone in the 

 river front, which Mr. Smith attributes to the judgment shown by 

 the principal carver in the selection of the stone, Mr. Grissell assures 

 us that — 



The whole of these large blocks were obtained from various parts of the quar- 

 ries, where the sizes could best be obtained, and were in no case selected by the 

 talented carver, Mr. John Thomas, who had charge of that portion of the work, 

 but were got invariably more with regard to size than to quality. The result of 

 which goes to prove that the more thoroughly the stone is exposed to the action 

 of the wind, rain, and sunshine, the less liable it is to decay. I may add also 

 that all these stones are fixed the reverse way to the bed, and (adds Mr. Grissell), 

 I believe, had they been used in more sheltered situations, would not so strongly 

 have commended themselves to Mr. Smith's kind notice and consideration. 



At a late period (in October) a very interesting letter from "An 

 Architect," appeared in the Times, investigating the circumstances 

 tinder which our Palace of Parliament, which has already cost up- 

 wards of two millions of money, notwithstanding the care and science 

 bestowed upon it, is found to be in a state of decay. This very com- 

 petent correspondent of the Times narrates of the Commission as 

 follows : — 



' : When the Palace of Westminster was to be built, at great expense 

 a Commission, consisting of the architect, two geologists, and a 

 chymist, went all over England to examine stone and buildings, and 

 they believed that in Yorkshire they had found what they wanted in 

 a bed of stone called mineralogically 'dolomite,' or, more generally, 

 magnesian limestone. It is a crystalline stone, composed of sulphate of 

 lime and sulphate of magnesia, and much harder than even Portland 

 stone. The best accounts 1 can find of its composition are in De la 

 Beche's Geological Manual, 1832, or in Van Bach's A nnales des Sci- 

 ences Naturelles, 1827, to which De la Beche refers. Let me remark, 

 however, that dolomite is a crystalline rock — that is, a chymical com- 

 bination of lime and magnesia, some thinking that it was originally 

 limestone, but altered by heat and other circumstances. I believe the 

 Commission were a little misled by their chymistry, but they found in 

 Coningsburgh Castle, in the neighbourhood of the quarries, a building 

 which certainly appears to have braved, with but little loss, the 

 war of the elements for 700 or 800 years. I believe, however, that 

 the outside of York Cathedral is a dolomite ; and certainly the 

 various states of decay of that building might have taught us caution 

 in its adoption. From the crystalline composition of this stone, 

 however, all the present mischief arises ; for when the crystallization 

 is complete, and the magnesia and lime in proper proportions, it is 

 indestructible ; but nature does not work quite uniformly on so large 

 a scale, and imperfect crystallization, or an excess of lime or 

 magnesia, would naturally lead to all we see at Westminster. Some 

 beds — nay, very large portions of the external facing, then, look as 

 good as ever ; but others, and unluckily those the best decorated, 

 and the upper portions of this splendid edifice, are already in a state 

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