112 



GEOLOGY OF THE SECOND DISTRICT. 

 40. 



A sketch showing the fractuieJ state of the Trenton limestone at Watertown, Jefferson county. 



5. Trenton Limestone. 



The remarkable scries of limestones of the Champlain group, arc terminated by the Tren- 

 ton, which, I may justly remark, is one of the best characterized rocks in the Transition sys- 

 tem, both in its fossils and lithological characters. In all the localities of this rock, we find 

 it more or less a shaly limestone. It sometimes occurs as a black thick-bedded rock, with 

 argillaceous matter diffused through it ; or in thin beds of limestone, alternating with those of 

 a thin shivery shale. In addition to the masses of limestone and shale arranged as here de- 

 scribed, there is sometimes another important one in the form of a grey crystalline rock, oc- 

 cupying sometimes a position inferior, and at others superior, to the black shaly limestone. 

 The black limestone is quite compact in structure, and is susceptible of a good polish, when 

 free from argillaceous matter. The exposed and upper part of the grey variety is often irre- 

 gularly bedded, loose in texture, and not sufficiently strong for a good building stone ; while 

 those beds which are deeper, are firmer, more even, and form a fine material for superstruc- 

 tures. The noble Cathedral of Montreal is composed of the grey variety of the Trenton 

 limestone. The grey, black and slaty limestones are often highly bituminous ; they not only 

 emit tiic odour when struck, but a moisture exhales from and covers the surface of the layers 

 of those newly exposed in the quarries, which strongly soils wlien handled, and imparts to 

 the hands and clothes the same odor. The relations of the grey and black limestones are not 

 uniform ; the former is sometimes beneath the latter, instead of resting upon it, as at or near 

 Watertovm in Jefferson county ; or else, there are two masses of this color and structure. 



