VARIETIES. 327 



" In none of the localities of this calcareous mass, which I have examined, from the flank of Snake 

 Mountain to near the Canada line, have I found any well-marked organic remains. This fact of itself, 

 strongly favors the idea of its being but a peculiar development of the upper portion of the Medina Group. 

 Nor can it be objected to, that this metamorphic action may have caused its present destitution of fossils. 

 Throughout nearly the whole of the series of exposures, extending due north toward the Canada line, it 

 presents a gentle eastern dip, conforming to the subjacent fossiliferous beds of matinal limestone and slate, 

 from which it is separated only by the sandstones above described. From this we infer that it must have 

 been as little exposed as these fossiliferous beds to agencies capable of obliterating its included fossils, and 

 that therefore it has never been in any considerable degree a fossiliferous mass. 



" We are further strengthened in the opinion that this calcareous group, with the subjacent sandstone, 

 belongs to the Medina period, by the consideration that the Clinton Group, with which it might otherwise 

 be compared, is almost every where an eminently fossiliferous one. From Alabama to northern New York 

 it is marked by an abundance of fossils. According to Mr. Logan, strata of this age are found in the 

 vicinity of Lake Memphremagog, and, although there surrounded by metamorphic masses, they include a 

 number of fossils in good preservation. 



" On the whole, therefore, I think that the limestone and subjacent sandstone of which we are now 

 treating, must be regarded as one formation, and may, with the highest probability, be referred to the 

 period of the Levant rocks or the Medina Group of New York." 



The following varieties of rock are associated together in the Ked Sandrock scries : 



1. KED SANDSTONE. 



2. WHITE SANDSTONE, OCCASIONALLY VERY COMPACT. 



3. SEVERAL KINDS OF BRECCIAS. 



4. SEVERAL KINDS OF LIMESTONE, SOMETIMES BECOMING CALCAREOUS SANDSTONES. 



5. RED AND VARIEGATED DOLOMITES. 



6. GREENISH SHALES. 



7. NOVACULITE SCHISTS. 



8. SEAMS OF CLAY SLATE. 



This formation embraces a great variety of rocks, and there is some difficulty expe- 

 rienced in associating them together, because of the general absence of fossils. The first 

 variety is a reddish brown or chocolate-colored sandstone. It becomes calcareous, and is 

 frequently interstratified with dolomitic layers of corresponding color. The grains of 

 sand composing the rock are often transparent, sometimes mixed with minute fragments 

 of feldspar. A slight metamorphic action has sometimes rendered the grains nearly 

 invisible, and made the whole rock compact. An analysis of this common variety of 

 sandstone from Charlotte gives 



Silica, .... 83.80 



Alumina and Peroxyd of Iron, 8.70 



Lime, . . . . 1.12 



Magnesia, .... .10 



Potassa, .... 4.59 



Soda, .... .45 



Loss by ignition, . . . .80 



99.06' 



This is the common rock of this formation, from which the name of red sandrock, 

 given by Prof. Adams, was taken. It is seen exposed in a range of hills from Bridport 

 to Burlington. In Orwell and Benson there is a sandstone, referred with doubt to this 



