18 



NATURAL HISTORY 



This rag is rugged and stubborn, and 

 will not hew to a smooth face ; but is 

 very durable : yet, as these strata are 

 shallow and lie deep, large quantities 

 cannot be procured but at considerable 

 expense. Among the blue rags turn up 

 some blocks tinged with a stain of yellow 

 or nisi colour, which seem to be nearly as 

 lasting as the blue ; and every now and 

 then balls of a friable substance, like 

 rust of iron, called rust balls. 



In Wolmer Forest I see but one sort 

 of stone, called by the workmen sand, 

 or forest, stone. This is generally of the 

 colour of rusty iron, and might probably 

 be worked as iron ore ; is very hard and 

 heavy, and of a firm, compact texture, 

 and composed of a small roundish crys- 

 talline grit, cemented together by a 

 brown, terrene, ferruginous matter ; will 

 not cut without difficulty, nor easily 

 strike fire with steel. Being often found 

 in broad flat pieces, it makes good pave- 

 ment for paths about houses, never be- 



