ADAMS COUNTY. 59 



tion of fossil fuel. Over all the northeastern portion of the county, No. 2 has 

 been found wherever the Measures have been penetrated to the proper depth, 

 or where the right horizon has been exposed by natural causes. The principal 

 drawback to the successful mining of this seam, is the shaly character of the 

 roof, which is usually a blue clay shale, though it has been seen at a few local- 

 ities where it was overlaid by a bituminous shale, which forms a good roof. 

 This coal seam will afford, according to the usual mining estimates, about two 

 million tons of coal to each square mile of surface which it underlies, and 

 although at the present time, there is but little demand for coal except along 

 the railroad lines, yet the time is not very remote, when a good coal, two feet 

 or more in thickness, will be considered of sufficient value and importance to 

 be opened, wherever it can be reached at a depth not exceeding one hundred 

 to one hundred and fifty feet below the surface. 



Building Stone. All the principal limestone groups of this county, furnish 

 more or less building stone of good quality, and there are but few points in the 

 western part of the county, where some of them are not easily accessible in the 

 bluffs or valleys of the streams. The Burlington limestone, which is exten- 

 sively quarried at Quincy, is one of the most important and valuable deposits 

 of building stone in the county, and as its aggregate thickness is about one 

 hundred feet, nearly all of which may be used as a building stone, the supply 

 from this formation alone might be fairly considered as inexhaustible. It is 

 for the most part, a light gray, or nearly white semi-crystalline limestone, which 

 cuts easily when free from chert, and is an excellent stone for dry walls, as 

 well as for caps and sills, and all the ordinary purposes for which cut stone are 

 required. The buff and brown layers contain a small per cent, of iron and 

 magnesia, and the surface becomes more or less stained by long exposure, but 

 the light gray beds are a nearly pure carbonate of lime in their composition, 

 and generally retain their original color. The lower portion of the Keokuk 

 limestone is similar to the Burlington in its composition, but is usually of a 

 little darker bluish gray color. The brown magnesian limestone of the St. 

 Louis group, is an evenly stratified rock, admirably adapted for common use 

 in foundation walls, and especially for bridge abutments and culverts, where a 

 rock is required to withstand the combined action of frost and moisture. This 

 rock may be found in the bluffs of McGrce's creek, through nearly its whole 

 course in this county, and also on Bear creek and its tributaries, in the north- 

 west part of the county. The bed is variable in thickness, ranging from five 

 to twenty feet, and it often affords massive strata from two to three feet thick. 

 In the vicinity of Ferguson's coal bank, four miles northwest of Camp Point, 

 there is an outcrop of brown sandstone overlying coal No. 3, which seems to 

 stand exposure well, as it forms a mural cliff, nearly twenty feet high, along 



