122 CHAMPLAIN DIVISION. 



Before I pass to the consideration of the succeeding members of this gronp, I desire to 

 call the attention of geologists to a narrow and irregular bell of the Calciferous sandstone 

 which extends from Greenbush to the Canada line. It is apparently fragmentary, and is 

 in some places undoubtedly so. It is fossiliferous, but most of the fossils are mere frag- 

 ments, consisting of pieces of the crust of the Illenus and Isotelus ; but among these 

 fragments, some small specimens of crustaceans may be seen, nearly perfect. 



This mass is very liable to be confounded with the Sparry limestone, inasmuch as it is 

 traversed by veins of calc-spar ; and where the soil conceals its borders, it is apparently 

 interlaniinated with the Taconic slate ; yet in many places it may be taken off from the 

 upturned edges of the slate, and is absolutely and entirely removed from these where it 

 has been quarried in several localities. This shows plainly, then, that it is a rock of an- 

 other age, from the slates upon which it rests ; and as this rock is broken up, and as into 

 it we find there has been introduced peculiar fossils, it shows that there was a change, a 

 beginning of a new era, which we may with great propriety consider as the commence- 

 ment of a new system. 



§ 3. Chazy limestone. 



Notwithstanding the remark that the lower limestones of the Champlain division may, 

 with at least a show of propriety, be placed under one name ; still it is right, in our esti- 

 mation, to designate certain masses under local names, where they are found in thick beds. 

 This especially seems right in the case of this limestone, which exists in Clinton county, 

 and whose entire thickness is at least one hundred and thirty feet. At Chazy, it is a dark 

 durable limestone, more or less cherty and thick-bedded ; but so little disposed to split in 

 any direction, that it is quarried with difficulty. This limestone is quite limited : it is best 

 developed at Chcfty, but still may be observed at Essex, where the characteristic fossil, the 

 Maclurea, is quite abundant. 



§ 4. BiRDSEYE LIMESTONE. 



This is the only perfectly compact limestone which occurs in the Champlain division. 

 It breaks with a conchoidal fracture. The color is a light drab, passing into a dark blue. 

 The light-colored variety has been pronounced a good lithographic stone. At Chazy, it is 

 interlaminated with a few beds of fine granular siliceous limestone, similar to the Jiydraulic 

 variety in the Calciferous sandstone. This variety is the raosr important for making quick- 

 lime ; for althougli it is often quite dark-colored, still it forms a remarkably pure white lime, 

 and well adapted for glass-making, and for any of those arts where a pure lime is required. 

 Such are some of the beds at Chazy. Some of the beds are singularly filled with calca- 

 reous spar : it often replaces the curious fossil hitherto known as the Fucoides demisstcs, 

 but which (as will be seen by reference to my report) is strictly a polyparia. This is con- 

 sidered the characteristic fossil ; though near its junction with the next mass of limestone 

 several fossils allied to those in the Trenton limestone are somewhat abundant. The 

 Ort/ioceras multicameratus is, however, equally characteristic with the Fucoides demissus. 



