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 through 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 stream 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 np-sfcream end of the gorge. This dip is small, 

 not more than a few inches to the hundred 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 accunmlato 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 GO cubic feet per second. A series of measure- 

 ments of the flow, made January-May, 1907, gave a minimnm flow of 56 

 cu. ft. per second on February 20, and a maximum flood stage of 4,500 cu. 

 ft. per second on March 1.3. Measurements made in August, 190S, 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 goi'ge 

 between the Main street bridge and the bridge at Test's Mills, about two 

 miles to the south. A survey by trauvsit and stadia was made and from 

 this a topographic map ou 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 Avere indicated by tints. Considerable areas of the re- 

 gion have been disturbed by cultivation, building operations, etc., and no 

 attempt to study those an'as was made. Photographs to show the more 

 striking features of the regicni were made- whenever possible. The nornen- 

 dature used is that of Gray s Manual, 7th edition. 



