19 
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.R.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 
Proceedings— Lit. & Phil. Soc. — Yol, XII. — No. 3.— Session 1872-3. 
