330 REPORT OF NATIONAL MUSEUM, 1904. 



"laborious and diligent," yet the reader who searches from cover to 

 cover for other facts than lithological characteristics, dip, and strike 

 will search in vain. The fact that the trappean outbursts were not in 

 straight and continuous lines, but curvilinear in form and occupying 

 a series of nearly parallel fissures, was practically the only break in 

 the monotony of detail. He wrote to a friend: 



I had twice surveyed the whole State on a regular plan of sections from east to 

 west, reducing the intervals in the last survey to an average distance of 2 miles, 

 thus passing along one side of each of the nearly 5,000 square miles of the 

 State. * * * I had examined all objects of geological interest, particularly the 

 rocks and their included minerals, with minute attention. I had scarcely passed a 

 ledge or point of rock without particular examination. 



Peevish and complaining, Percival evidently could not be made to 

 understand why he should not be allowed to go on indefinitely, render- 

 ing a report when he himself should be satisfied of its correctness. 

 With such a disposition the average country legislator naturally had 

 no patience, and the abridged report, a volume of 495 pages, with an 

 uncolored map, was finally printed in 1842, as already noted. 



Though written by a poet, it is utterly lacking in imagination, and, 

 aside from its dullness, remarkable only from the fact that it is stated 

 to have been written largely from memory. The subjects considered, 

 in the order given, were: First, the rocks or consolidated formations; 

 second, the loose or unconsolidated formations; third, the soils; fourth, 

 economic results, and fifth, the physical geography. The rocks were 

 all classed under three heads: First, the primary; second, the sec- 

 ondary, and third, traps, the distinctions made being on almost purely 

 lithological grounds. 



In 1853 Percival was employed by the American Mining Company 

 in exploring the lead mines of Illinois and Wisconsin, and in 1854 was 

 appointed State geologist of Wisconsin, as noted elsewhere. He died 

 in 1856. 



In the American Journal of Science for 1836 S. P. Hildreth, later 

 connected with the geological survey of Ohio, published what was, for 

 its time, an important paper relative to the bituminous coal deposits of 



Ohio and the general geology of the Ohio Valley. 

 woVin oh?o, 1836. Although Hildreth was inclined to indulge in specu- 

 lations founded upon scanty data, his paper is, never- 

 theless, important for the numerous sections of the coal strata and as 

 illustrating the condition of knowledge at that day relative to both 

 coal and petroleum. 



Hildreth was one of the first to recognize the enormous amount of 

 subaerial erosion that had taken place throughout the region, and that 

 the Ohio River had carved out its own channel. He felt, however, that 

 in times past the precipitation had been much greater than at present, 

 and the abrasion of the surface by rain and torrents much more rapid. 



