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Ordinary Meeting, November 26th, 1872. 



J. P. Joule, D.C.L., LL.D., F.R.S., &c., President, in the 



Chair. 



Dr. R. Angus Smith, F.K.S., said that he, like others, 

 had observed that the particles of stone most liable to be 

 in long contact with rain from town atmospheres, in England 

 at least, were most subject to decay. Believing the acid to 

 be the cause, he supposed that the endurance of a silicious 

 stone might be somewhat measured by measuring its re- 

 sistance to acids. He proposed therefore to use stronger 

 solutions, and thus to approach to the action of long periods 

 of time. He tried a few specimens in this way, and with 

 most promising results. Pieces of about an inch cube were 

 broken by the fall of a hammer and the number of blows 

 counted. Similar pieces were steeped in weak acid ; both 

 sulphuric acid and muriatic were tried, and the latter pre- 

 ferred. The number of blows now necessary was counted. 

 Some sandstones gave way at once and crumbled into sand, 

 some resisted long. Some very dense silicious stone was 

 little affected ; it had stood on a bridge unaltered for centu- 

 ries, in a country place however. These trials were mere 

 Peoceedings— Lit. & Phil. Soc— Vol, XIL— No. 3.— Session 1872-3. 



