432 GEOLOGY OF OHIO. 
ridge, and in respect of length and of alluvial bottom, is even more im- 
portant than the stream to which it is nominally tributary. Hast Fork 
rises near Martinsville, and has cut for itself a channel in some places, 
as within three or four miles of Clarksville, nearly one hundred feet deep 
in the Blue Limestone. 
The East Fork of the Miami drains that part of the county south of. the 
Cincinnati and Marietta railroad, including the neighborhood of New . 
Vienna, and the region south of “Snow Hill” ridge. 
All these streams have in years past furnished motive power for grist 
and saw-mills, which have, in most instances, been suffered to go to decay 
upon their banks, on account of the failure of a supply of water sufficient 
to turn their wheels during enough months of the year to make it profit- 
able to keep up the mills. This is due, in considerable degree, to the 
failure of the water in the streams during the late summer and early fall 
months. The water which fell during the winter and spring months, 
when the country was new and mostly covered with forest, was retained 
on the soil. The small streams were choked with rubbish, and the water. 
stood on flats, protected from speedy evaporation by the dense foliage of 
the trees, and by the heavy coating of fallen leaves which covered the 
earth. No artificial drains were in existence. The water gradually 
trickled from these natural reservoirs, highly colored with the soluble 
elements of the partially decayed vegetable substances, and kept the 
streams with at least a partial supply of water during the most of the dry 
season. ‘Then the mills and dams were less expensive than now, partie- 
ularly the dams, which were no more than cheap structures of logs and 
brush, intended chiefly to be of use in changing the current upon the 
wheel of the mill, rather than in detaining the water in a reservoir. 
Then the machinery of mills was simple and inexpensive, and was suf- 
fered to lie idle without detriment during the season when water was 
insufficient to turn it. Now numerous improvements have been made 
in mill machinery, without which such quality of flour as is now in de- 
mand cannot be made, and these, being patented, are more expensive 
than the machinery which they displaced. More expensive dams are 
necessary to retain a large quantity of water. Formerly the miller was 
also generally a farmer, and could make profitable use of the dry season in 
tilling his farm. For such reasons as these, although the same quantity 
of water still flows through the same channels, the mills are in decay, 
and the mill seats abandoned. 
DRAINAGE OF FAYETTE COUNTY. 
A glance at the map of this county shows numerous water-courses 
traversing the county from its northern to its southern border, varying 
