16 THE GEOLOGIST'S TKAVELING HAND-BOOK. 



3 a. Calciferous. This group embraces in New York three distinct masses 

 as to character and position, and these alternate and intermix with each other. The 

 first is silicious, compact, and may probably be the continuation of the Potsdam 

 sandstone. The second is a variable mixture of fine, yellow, silicious sand and 

 dolomite or magnesian carbonate of lime, which, when fractured, presents a fine, 

 sparkling grain. It is in irregular layers, which have a shattered appearance, 

 from numerous cracks, the parts being more or less separated from each other. 

 This is the mass from which the name Calciferous sandrock was derived. The 

 third is a mixture of the dolomitic material, which is usually yellowish, very- 

 granular when fresh broken, and of a compact limestone, which resembles the 

 Birdseye. The action of the weather gives these layers the appearance of Gothic 

 fret-work, and the color becomes a dark yellow-brown. V 21. As its name 

 indicates, it is a sandy magnesian limestone, but it is not destitute of beds of pure 

 limestone. The mixture of a variety of mineral matter causes the rock to weather 

 unequally; hence it is often rough externally, portions of the silicious part 

 standing out in relief. There are two quite uniform characters which distinguish 

 the Calciferous, viz : A fine crystalline structure intermixed with earthy matter, 

 and numerous small masses of calcareous spar. E. 105. Great numbers of quartz 

 crystals are found in the cavities of this formation, many of them very perfect as 

 to form and transparency. V. 30. 



In the Mississippi basin this formation is called the LOWER MAGNESIAN 

 LIMESTONE, to distinguish it from the Upper or Trenton limestone. The eastern 

 name, Calciferous or lime-bearing sandrock, does not apply, as it is almost 

 free from sand. As its western name indicates, it is a dolomite or magnesian 

 limestone, and makes an excellent lime for building-purposes. It usually contains 

 about one equivalent or forty-five per cent, of carbonate of magnesia. This 

 limestone forms the summits of the bluffs of the Mississippi; it supports 

 high table-lands that extend back from the river, and forms prominent angles 

 to the summits of the bluffs on either side of that river. These even and 

 heavy layers are those usually quarried for building-stone. D. D. Owen gives 

 descriptions of the picturesque character of the landscape in the region of 

 the Upper Mississippi, and especially the striking similarity which the rock 

 exposures present to ruined structures, and his report is illustrated by beautiful 

 engravings showing the castellated appearance of the cliffs of the Lower Magnesian 

 limestone on the Iowa River. In Pennsylvania it is a coarse, gray calcareous 

 sandstone, containing cavities enclosing very minute crystals of quartz and 

 calcareous spar. 



3 b. Quebec. This group was divided by Sir W. E. Logan into three 

 parts, consisting, in the ascending order, of 1. Levis, 2. Lauzon, and 3. Sillery. 

 But it afterwards appeared that the section on which this order was based was an 

 inverted one, and that the Sillery was the oldest. 



The Quebec group is about 7,000 feet in thickness. The lowest, or 1. SILLEEY 

 subdivision, is a massive greenish sandstone, fine and coarse grained, frequently a 

 conglomerate of white quartz pebbles, and is 2,000 feet thick. The sandstones 

 are sometimes slightly micaceous, with small scales of green and black shale. They 

 usually present massive beds, and at Sillery some of the layers are quarried and 

 used for building purposes at Quebec. The 2. LEVIS, or middle portion of the 

 Quebec, is 1400 feet thick. It is named from Point Levis, opposite Quebec, and 

 consists chiefly of fossiliferous limestone-conglomerates. The 3. LAUZON or upper 



