PSEUDOBRECCIATION IN ORDOVICIAN LIMESTONES 405 
bore together expose 97 ft. of stone, the lower 62 ft. of which is 
buff, and so thinly bedded as to be valueless as a dimension stone. 
In this is found, at a depth of 51 ft. below the top of the limestone 
in this exposure, a bed 16 ft. thick which might be described as a 
very impure limestone, high in argillaceous material. 
Fic. 2.—Upper Mottled limestone, Henry’s Quarry. Tyndall 
The rock consists of a light-grey limestone, with patches of 
darker material scattered through the stone. Though these darker 
areas are distributed apparently quite irregularly, slabs cut parallel 
and perpendicular to the bedding planes show that the linear 
extension of the patches is decidedly along the bedding planes. A 
comparison of the side of the slab shown in Fig. 3 (cut along the 
bedding plane) with its end section will be convincing. There is 
no evidence, on the other hand, of greater development of the 
darker areas along jointing planes than in any other vertical direc- 
