284 
GEOLOGY OF THE FOURTH DISTRICT. 
Sketch of the northern edge of the Conglomerate, six miles south of Olean in Allegany county. By Mr. E. N. Horsford.* 
CHAPTER VII. 
CARBONIFEROUS SYSTEM. 
CONGLOMERATE, OR EQUIVALENT OF THE MILLSTONE GRIT OF ENGLAND. 
Under the term Carboniferous system, it is intended to include all those deposits which are 
considered as belonging to that period in which the great coal-fields were produced. These 
are marked throughout by characters which indicate a certain prevailing condition in the ocean 
and the nature of the deposits, and a similarity in the nature of the organic products. All the 
workable coal seams of the country are confined to this formation, and none have ever been 
known to occur in the rocks previously described in this Report. 
The illustrations of this chapter, and that upon jointed structure, were mostly sketched by Mr. Horsford, 
