36 CHAZY GROUP. 



§ 71. Bitumen, or mineral pitch, is a product resulting from the distillation of 

 vegetable and animal matter within the earth. It has a pitch-like odor, and burns 

 with a bright flame without any ash, and varies from liquid naphtha to solid as- 

 phaltum. Naphtha is a nearly colorless fluid, having a pungent smell, that issues 

 from the rocks in Persia. Its specific gravity is about 7-10, and by exposure it 

 loses its transparency and odor, and acquires a yellowish or brown color, becomes 

 thicker and heavier, and approaches petroleum. Petroleum is so called from exud- 

 iug as an oil from the rocks. Its specific gravity is 87-100, and by exposure to 

 the air and the application of heat it may be converted into asphaltura. Asphal- 

 tum was so named from a lake in Judea, where it rises in a liquid form to the 

 surface of the water and then hardens. Its specific gravity varies from 1.07 to 

 1.65. It is quite brittle and electric, though coal is not. Bituminous matter occurs 

 in the limestones and dolomites of the Quebec Group, and the odor may be de- 

 tected in many places by striking or heating the rocks. A black, combustible, 

 coal-like matter is found with crystals of bitter spar and quartz, sometimes coating 

 the crystals or the walls of cavities, and at other times in the form of buttons or 

 drops, evidently having been introduced in a liquid state and subsequently hard- 

 ened. It fills veins and fissures in limestones, shales, and sandstones, and even in 

 the trap-rocks which traverse these. It is very pulverulent, brittle, of a shining 

 black color, and yields from ten to twenty per cent of volatile matter. It approaches 

 anthracite in its characters. The volatile matter is a hydrocarbon gas. It has re- 

 sulted from the slow alteration of liquid bitumen in the fissures of the strata. The 

 bitumen was derived from marine vegetation or marine animals, which underwent 

 a special mineralization, producing the bituminous matter instead of coal. It is due 

 to chemical reactions, by which it retained a greater proportion of hydrogen in its 

 combination than would have been retained if it had been converted into coal. 



CHAPTER VII. 



CHAZY QROUP. 



§ 72. The Chazy Group was first defined in the Eeport of the Second District 

 of New York in 1842, by Prof. Emmons, under the name of the Chazy limestone. 

 The name was derived from the town of Chazy, where it has a thickness of 130 

 feet, reposes unconformably upon the Calciferous, and is succeeded by the Birds- 

 eye limestone. It is a dark, irregular, thick-bedded limestone, containing many 

 rough, flinty, or cherty masses, and extends as a belt into Vermont, where it ex- 

 poses more surface area than any other Group of the Lower Silurian, and has a 

 maximum thickness of 300 feet. It was called the "Chazy Formation" in the 

 Geology of Canada for 1863, because shales and sandstones are there associated 

 with the limestone. It occupies a narrow area about the Ottawa and Montreal, 

 and extends to the Mingan Islands and Newfoundland, its thickness not exceeding 

 300 feet. The western extension of the belt appears in cliffs on the coast of Lake 

 Winnipeg, in the region of Lakes Huron and Superior, in Michigan, Wisconsin, 

 Iowa, and Minnesota. In the lake region it consists of arenaceous and arenaceo- 



