438 GEOLOGY OF OHIO. 
Other large bowlders are found in the extreme northern part of Fayette 
county, scattered numerously over the surface of the ground, and weich- 
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 on 
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, 
succesful 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 dep sit, thoze 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- 
nezs above the bedded stone. This material was manifestly deposited 
from water. And to account for the character of the markings upon the 
rock 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 for 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 ina 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 preéxisting 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 more or less distinctness. During the emergence of the 
