Reviews — Geological Siirveij of Ohio. 557 



and his assistants have been spent in elucidating the distribution 

 and arrangement of this formation. Forming the western extension 

 of the great Alleghany Coal-basin, and having a slight general dip 

 to the south-east, it was supjoosed that many of the coals worked 

 along the eastern border of the State cropped out very soon, and 

 that the seams seen to the west of the Coal-field were carried by the 

 supposed uniform easterly dip so far below the surface as to be 

 practically inaccessible. The present observers have clearly shown 

 that this is not the case. They have proved the existence of at 

 least two gentle folds in the strata running parallel to the strike, the 

 result of which is, that certain good coals or their horizons are 

 within easy reach all along the valleys that cut the north-eastern 

 portion of the basin. The average dip to the south-east is thus 

 shown to be utterly insignificant — not more than three feet to the 

 mile. A further and possibly a less pleasing consequence of the 

 determination of these rolls is, that the Coal-seams which were 

 formerly assumed to exist below the so-called Barren Measures 

 have been reduced to half their former number. It may be noted 

 that a river runs along the bottom of each of these synclinals, the 

 Killbuck and the Tuscarawas. 



The entire thickness of the Coal-measures to be found in Ohio is 

 taken at about 1500 feet, in which are ten seams of workable coal. 

 These are of no great thickness, but are of excellent quality. That 

 they are well worth working is shown by the fact, that the annual 

 production of coal in Ohio is 3,000,000 tons. All the coals are 

 bituminous, i.e. furnace, coking, and cannel coals, — the coking variety 

 being the most prevalent. 



Iron also seems to be plentifully distributed throughout the Coal- 

 measures, in the form of black band and kidney ore, etc., in a manner 

 perfectly similar to that which obtains in Britain. Indeed, no geo- 

 logist looking over the sections which illustrate this portion of the 

 Ohio Reports, can fail to be struck with the great resemblance they 

 bear to typical ones from our own Coal-fields — say, for example, that 

 of Durham. The same alternation of sandstones and shales, with 

 occasional beds of fire-clay and seams of coal, is to be found in both 

 cases, and the only difference lies in the presence in the American 

 series of one or two beds of Limestone, which, notwithstanding their 

 small thickness, appear to be the most constant. 



Immediately below the Coal-measures, Dr. Newberry places a 

 conglomerate, formed chiefly of white quartz pebbles, as the repre- 

 sentative of the Millstone Grit. This deposit is, however, often absent; 

 and in its southern portion at least Prof. Andrews is by no means 

 sure that it is anything more than local accumulations of pebbles. 

 Still worse represented is the next great division, that which is 

 equivalent to our Carboniferous Limestone. This consists in Ohio of 

 a calcareous bed known as the " Maxville Limestone," which is 

 shown on the geological map by a few patches of small extent, and 

 far between, along the lower boundary of the Coal-measures and 

 conglomerate, and in the south of the State only. 



An important group of rocks, however, next appears, and covers 



