438 GEOLOGY OP OHIO. 



Other large bowlders are found in the extreme northern part of Fayette 

 county, scattered numerously over the surface of the ground, and weigh- 

 ing from twenty to thirty tons. Besides these large erratic blocks, 

 smaller ones are found more or less abundantly everywhere throughout 

 these counties, especially in the northern half They are found lying oa 

 or near the surface, where they have been left by the removal by water 

 of the material deposited with them. 



GRAVEL AND SAND. 



Mingled with the drift is always found a considerable proportion of 

 these substances, but being scattered throughout the whole mass, or at. 

 most, showing only a slight tendency to be distinct in strata, more or less 

 mixed with soft material. Where the original drift is in quantity and 

 undisturbed, the sand and gravel in it are not available for economic 

 purposes. A few years ago these counties were thought to be lacking in 

 these important adjuncts to civilization. It was not until within the 

 last five years, when the demand for gravel for road-making became ex- 

 ceedingly urgent, that thorough and exhaustive, and, as the result proved, 

 successful search was made for it. It is now known that no real deficiency 

 exists. People have learned where to look for it. When the currents of 

 water carried away the lighter material of the drift depDsit, those con- 

 stituents which were heavier were left behind. We may regard^ the 

 highest land as the former level of the region we are speaking of. There 

 was then a deposit of loose material, sometimes a hundred feet in thick- 

 ness above the bedded stone. This material was manifestly deposited 

 from water. And to account for the character of the markings upon the 

 rook surface and the promiscuous intermixture of clays, sand, and gravel, 

 and sometimes a certain limited measure of stratification, or assorting of 

 the material according to their weight, and for the evidently remote 

 origin of the stony constituents requiring that they should have been 

 brought hither, and especially for the numerous bowlders conspicuous 

 both f&r their size and clear marks of foreign origin, we unhesitatingly 

 come to the conclusion that ice in some form contributed to the same 

 end. Water in a liquid state alone could not carry such material so far 

 without having an enormous velocity sufficient to move before it not only 

 the loose material, but the very stone beneath it. When the water sub- 

 sided, new lines of drainage appeared, corresponding more or less, depend- 

 ing upon the physical features of the country, with preexisting ones. The 

 emergence of the land was gradual, and the subsiding water stood for 

 greater or less periods of time at different levels, which may be pointed 

 out to-day with mare or less distinctness. During the emergence of the 



