Bae THE OLD RED SANDSTONE. 
There is no field:in which more laurels await the philosophi- 
cal chemist thanthe geological one. I have said that all the 
calcareous nodules of the ichthyolite beds seem to have had 
originally their nucleus of organic matter. In nine cases out 
of ten the organism can be distinctly traced ; and in the tenth 
there is almost always something to indicate where it lay — an 
elliptical patch of black, or an oblong spot, from whicn the 
prevailing color of the stone has been discharged, and a 
lighter hue substituted. Is the reader acquainted with Mr. 
Pepys’s accidental experiment, as related by Mr. Lyell, and 
recorded in the first volume of the Geological Transactions ? 
It affords an interesting proof that animal matter, in a state 
of putrefaction, proves a powerful agent in the decomposition 
of mineral substances held in solution, and of their conse- 
quent precipitation. An earthen pitcher, containing several 
quarts of sulphate of iron, had been suffered to remain undis- 
turbed and unexamined in a corner of Mr. Pepys’s laboratory 
for about a twelvemonth. Some luckless mice had mean- 
while fallen into it, and been drowned; and when it at length 
came to be examined, an oily scum, and a yellow, sulphu- 
reous powder, mixed with hairs, were seen floating on the 
top, and the bones of the mice discovered lying at the bottom ; 
and it was found, that over the decaying bodies the mineral 
components of the fluid had been separated and precipitated 
in a dark-colored sediment, consisting of grains of pyrites 
and of sulphur, of copperas in its green and crystalline form, 
and of black oxide of iron. The animal and mineral mat- 
ters had mutually acted upon one another; and the metallic 
sulphate, deprived of its oxygen in the process, had thus cast 
down its ingredients. It would seem that over the putrefying 
bodies of the fish of the Lower Old Red Sandstone the water 
nad deposited in like manner, the lime with which it was 
