232 GEOLOGY OF THE BLACK HILLS. 



a renewal of the excitement for a time, an account of wl)ieli will Ije given 

 farther on. 



In examining the gravel deposits along the valley of French Creek 

 advantage was taken of the numerous prospecting shafts already sunk by 

 the miners, and in the few places remaining untried which gave any indi- 

 cation on the surface of the existence of valuable underlying gravel beds, 

 shafts were sunk to bed-rock by the miners assisting me in the work. 

 Tlio first tests were made by washing several pans of the pay gravel in the 

 usual manner, and if the result obtained was at all encouraging the deposit 

 was more extensively tested by washing a measured quantity of the pay dirt 

 in a rocker and weighing the gold obtained. Finding that the best prospects 

 in the gulch were from gravel from a prospecting shaft on a dry branch of 

 French Creek about five miles above the stockade, the following test was 

 made to determine as accurately as possible the richness of the deposit : 



The sliaft was first cleaned out and a sufficient quantity of the pay 

 gravel drifted out from ofi" bed-rock, carefully averaged, measured, and 

 washed with the greatest care in a rocker, every precaution being taken 

 to prevent any appreciable loss of fine gold carried over the riffles by the 

 muddy water. The result was as follows: 9 buckets gravel = 3.12 cubic 

 feet, gave 0.370 gram of gold in small flat scales and grains ; 0.370 gram 

 z=. 5.7 grains troy r= $0.23, or aboiit one and one-fourth cents to the pan. 



This would indicate a yield of $1.87 per cubic yard of the pay gravel 

 which formed a layer on bed-rock about a foot in thickness. 



In the above calculation an average bucket of gravel is taken at 600 

 cubic inches, or 75 buckets equal one cubic yard. A pan is about lialf a 

 bucket, giving 150 pans of dirt to a cubic yard. I have estimated the value 

 of the gold to be $19.50 per ounce in gold coin. 



The gravel from a shaft some distance below on the stream, tested in 

 a similar manner, gave the following result : 10 buckets dirt = 3.42 cubic 

 feet, yielded 0.020 gram gold; 0.020 gram = 0.3 grains troy = 0.012 cent, 

 or 9 cents per cubic yard, equal to one-twentieth of a cent to the pan. This 

 latter gravel was very poor in gold, but tliat washed in the preceding test 

 was correspondingl}' richer than the average of the gravel opened at that 

 time along the creek. Near the stockade the result of the prospecting 



