MODE III. LIMESTONE. 457 



oolite, from the eggs or roe of fish : but as this ap- 

 pellation might imply that the grains equal the 

 eggs of birds, it is ambiguous ; not to add that, 

 as the substance was really supposed to be the 

 petrified roes of fish, whence the English roe- 

 stone, it is better to dismiss a term leading to erro- 

 neous ideas. The analogy between pisolite and 

 sinapite is also preferable, both being derived from 

 the vegetable kingdom. 



This substance is far more abundant than piso- 

 lite. According to Gmelin, it is frequent in the 

 stratified mountains of Gothland, Saxony, Thu- 

 ringia, Brunswick, France, Swisserland; forming 

 ample and often repeated strata, of a dull grey or 

 brown colour ; and sometimes, though rarely, pre- 

 senting animal remains. 



The Ketton stone of Rutlandshire is a fine ex- 

 ample of this kind of rock. 



Sinapite, from Iceland. 



The same, from Ketton. 



The same, of a still finer grain, from Bath. 



The same, from the various countries mentioned 

 by Gmelin, where, as it forms vast beds, it cannot 

 be classed among the depositions. 





