226 
of seepage and slumping is frequent. A large talus quickly collects. This 
is composed of angular fragments of the limestone, embedded in a matrix 
of the fine mud produced by the weathering of the shale. 
The stream threugh the gorge has a very high gradient. From Main 
street to Test’s Mills. a distance of about 9,000 feet, the total fall is 47 
feet, or about 1 foot in 200. This gradient is not at all uniform throughout 
the distance. In general the strerm consists of a series of alternate ponded 
stretches and rapids. At some of the fall lines a difference of level of six 
or eight feet may occur. This condiition is produced by a slight dip of 
the rock strata toward the up-stream end of the gorge. This dip is small, 
not more than a few inches to the huudred feet. Where a portion of the 
rock, harder than the surrounding rock or with less shale, comes to the 
surface, a fall line is produced. Fragments of rock carried down by spring 
floods accumulate at this point, and the portion of the stream immediately 
above becomes ponded. Some of these ponds are as much as 1,200 feet in 
length. 
The annual rainfall in this region is about 40 inches. The average 
flow of the river is about 60 cubie feet per second. <A series of measure- 
ments of the flow, made January-May, 1907, gave a minimum flow of 56 
cu. ft. per second on February 20, and a maximum flood stage of 4,500 cu. 
ft. per second on March 13. Measurements made in August, 1908, indicated 
a flow of only 42 cu. ft. per second. 
It is a deplorable fact that up to the present time the city of Richmond 
has seen fit to dispose of its sewage by the primitive method of dumping 
it directly into the river. Since this sewage flow amounts to 12 to 15 
cubic feet per second, or one-fourth the total flow at low water stage, the 
condition of the river below the sewers may be imagined. 
The region selected for study includes the floor and bluffs of the gorge 
between the Main street bridge snd ihe bridge at Test’s Mills, about two 
miles to the south. A survey by transit and stadia was made and from 
this a topographic map on a scale of 1 inch to 250 feet was prepared. On 
this the various data were recorded, and the conditions of the various por- 
tions of the area were indicated by tints. Considerable areas of the re- 
gion have been disturbed by cultivation, building operations, ete., and no 
attempt. to study these areas was made. Photographs to show the more 
striking features of the region were made whenever possible. The nomen- 
clatnre used is that of Gray's Mannal, 7th edition, 
