386 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 
to the northwest of French Corral, and is distant from it about a mile. According to Mr. Miller, 
a fine quartz gravel can be traced along the ridge for a mile or more.* 
The old gravel channel, which follows the ridge between the south and middle forks of the 
Yuba River, is spoken of frequently as being continuous between French Corral and San Juan. 
This is not strictly true, as a glance at the map will show, — Woodpecker Ravine cutting quite 
across the old channel between Birchville and Buckeye Hill, Sweetland Creek between Buckeye 
Hill and Manzanita Hill. and Kent Ravine between American Hill and the mines at San Juan. 
These ravines, however, are all of modern origin, and there is no reason to doubt the former 
continuity of the gravel. 
The distance between the upper end of San Juan Hill and the lowest point in the channel at 
French Corral, according to the map, is six miles and three quarters. I took observations for altitude 
at the extreme points, and at three points intermediate. The grade seems to be pretty regular for 
the whole distance, and somewhat less than that previously given.t I make the difference of level 
between the extreme points only 454 feet, which reduces the grade to sixty-seven feet to the mile. 
The direction of the channel is southerly or southwesterly between the curves near the two ends 
of the portion now under consideration. At French Corral there is a broad sweeping curve from 
the south to the west, and at San Juan a similar curve changed the course of the old stream from 
west to south. When seen from some elevated point, as, for instance, from the top of the high 
hill which lies to the north of Woodpecker Ravine and west of Buckeye Hill, the old channel ap- 
pears to follow a rather narrow trough or depression lying between continuous ridges or a series of 
high points of country rock, irregularly cut by ravines, which rise on either side to an elevation of 
three or four hundred feet above the gravel; the ridge on the northwest separating the old channel 
from the present Middle Yuba, that on the southeast from the South Yuba or from Shady Creek. 
The diagram (Plate N, Fig. 4) represents a general section across the ridge in the neighborhood of 
Birchville. No detailed measurements were made, the figures being only approximate. 
The principal owners of the gravel claims between French Corral and San Juan are the Milton 
Company, and the company operating at American Hill. I did not make any attempt to get a 
list of names of all the owners, or to ascertain the precise boundaries of all the claims. The prin- 
cipal town-sites are given upon the General Map. The most important mining properties, to which 
allusion will be made in what follows, are the French Corral mines, comprising the portion ex- 
tending from the outlet at the western extremity for a distance of about three quarters of a mile ; 
those at Empire Flat, the Kansas and Nebraska, and those at Kate Hayes Flat, comprising the 
ground opposite the upper town at French Corral, and extending for about half a mile ; the 
Esperance and Bed Rock, extending to the lower end of the Birchville diggings; Buckeye Hill, 
between Birchville and Sweetland ; Manzanita Hill, the southern extremity of the large body of 
gravel lying between Sweetland Creek and Kent Ravine ; American Hill, at the upper end of the 
same body of gravel ; and the old mines at San Juan. 
The bed-rock is exposed at several points between the lower end of the French Corral mines 
and Kate Hayes Flat, at Birchville, at Buckeye Hill, at Manzanita Hill, at American Hill, and at 
San Juan. It changes its character several times in this distance. I collected a few specimens, 
but could not include all the varieties, nor make out all the relations of bedding in the time at my 
disposal for the study of this section of country. In general terms the bed-rock is either granitic 
(or syenitic) in character, or belongs to the series of metamorphic slates.{ Below Kate Hayes Flat, 
* JT have indicated its approximate position upon the Gravel Map. 
+ See ante, p. 202. 
t See the specimens numbered from 10 to 15. Three varieties of the rock from (1) Kate Hayes Flat, (2) lower 
end of Birchville diggings, and (3) the upper end of Birchville diggings have been examined microscopically by 
Mr. Wadsworth, and are said by him to correspond to the so-called quartz-diorite of the German lithologists. 
The three specimens all came from near the line of junction between the granitic rocks which extend to the east 
and north and the slates which lie to the west, and do not differ so much from the former as to preclude the pos- 
sibility of their being portions of the same mass, locally affected by the proximity of the slates. I have accord- 
ingly felt justified in speaking of them as granitic. 
