396 REPORT ON NATIONAL MUSEUM, 1880 



of the Museum collection. Within the city limits of Chicago there is 

 quarried from this same formation a coarser somewhat cellular stone, 

 that from its unique character perhaps merits a special description. 

 According to Hunt* this stone when pure is a nearly white granular 

 crystalline dolomite, containing 54.6 per cent, carbonate of lime. It, 

 however, contains so large a portion of bituminous matter, that blocks 

 sometimes become quite black on exposure. The color fades somewhat 

 in time, but the petroleum odor is often perceptible for long distances. 

 The stone has been used to some extent for building purposes, as notably 

 in the First Presbyterian Church in Chicago. The gummy bituminous 

 matter causes the dust from the streets to adhere to exposed surfaces, 

 thus giving the buildings a peculiar antique appearance. We are in- 

 formed by Mr. Batchen that this pseudo-antique appearance is greatly 

 admired by some. The presence of the bitumen is beneficial in at least 

 one respect, in that it renders the stone less pervious to moisture, and 

 hence less liable to disintegration by freezing. This stone is repre- 

 sented by an 18-inch cube in the Museum collections. 



Lower Silurian (Trenton) limestones and dolomities are quite exten- 

 sively quarried in Jo Daviess County, and make a handsome and very 

 durable building material. Calhoun, Alexandria, and Ogle Counties 

 also furnish good material, but which, for lack of space, can not be de- 

 scribed here. At various points in Whiteside and Hopkins Counties 

 there are outcrops of limestones belonging to the Cincinnati group, a 

 part of which will furnish durable building material. The stone needs, 

 however, to be selected with the greatest care, since all the beds are not 

 of equal quality. 



At Jonesborough, in Union County, there occurs a fine, even-grained, 

 compact, beautifully oolitic stone that cuts to a sharp even edge, and 

 seems admirably adapted for carved work and general building pur- 

 poses as well. Specimens in the National Museum are of a lighter color 

 than the Bedford, Ind., oolotic stone and take a better polish. We 

 have had no means of ascertaining its lasting qualites, but it is stated! 

 to be liable to injury from frost when exposed in damp places. The 

 stone is of the Carboniferous age. Other oolitic stones occur at Rose- 

 clair, in Hardin County. They are of a dark bluish-gray color and take 

 a good polish. 



There are many other localities in the State which furnish excellent 

 varieties of building stone. These can not be mentioned here for lack 

 of space. Interested parties are therefore referred to the catalogue of 

 the Museum collections and to the report of the Tenth Census. 



Indiana. — Few of the limestones at present quarried in the United 

 States exceed in reputation and beauty the fine-grained oolitic stone 

 of sub-Carboniferous age from the vicinity of Bedford, in this State, 

 and popularly known as "Bedford limestones." The rock is of fine and 



* Chemical and Geological Essays, p. 172. 

 t Report of Tenth Census, p. 225. 



