584 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION, 
data given me by Mr. Pearl, shows all there is to be known about this deposit at present. The 
position of the bed-rock under the gravel is hypothetical. 
It cannot be said with certainty that the old channel flowed directly from French Corral to 
Mooney Flat ; but the evidence is very much in favor of the hypothesis that those two places once 
lay upon the same stream. If this hypothesis is not accepted, two difficult questions arise for 
solution, namely: Where was the outlet for the French Corral channel? and, Where were the sources 
of the Mooney Flat channel? The two points are about nine miles apart in a direct line, and the 
bed-rock at French Corral is 822 feet higher than that at Mooney Flat. This allows a grade of 
ninety-one feet to the mile, a grade only four feet less than the average grade of the old channel 
between French Corral and Snow Point. The subject is complicated somewhat by the position of 
the gravel seen on the hill above Fiene’s toll-house and of that at Pearl’s tunnel. Both these 
masses of gravel are too high to belong to the old French Corral-Mooney Flat channel, unless there 
were irregularities of grade so extraordinary as to be almost inadmissible in theory, though they 
are very nearly in the line of the supposed stream. It is possible that they represent some tribu- 
tary stream, or lateral ravine. 
Section II].— Zhe Divide between the South and Middle Yuba Rivers. 
For the purposes of this report this region can be conveniently subdivided into five parts, which 
will be considered in the following order : — 
A. From Frencu Corrat to Nortu San Juan, 
B. Lone Ripee anp Montezuma HI, 
C. From Norra San Juan to Norta BiLoomriewp, 
D. From Norra Bioomrigtp To EvrREKA, AND 
E. Apove Eureka. 
Before passing to the details, however, a few words may be introduced of a more general character. 
Upon showing the Gravel Map to Mr. N. C. Miller, of French Corral, I learned that there were 
errors upon it which could not be corrected without great expenditures of time and money. Some 
of these errors may be due to inaccuracies of the original survey, and some of them are undoubtedly 
chargeable to the persons who ran the United States section lines in 1873. Certain it is that the 
relative positions of the section lines and the towns, as given on the map, are not the same as they 
are on the ground. The discrepancy amounts in some cases to as much as half a mile, saying 
nothing about those cases in which the error is even greater in amount but of such a character that 
it can be easily corrected.* Moreover, there is always room for considerable uncertainty as to the 
precise site of a town in the gravel mining districts. Take the town of Moore’s Flat, for instance ; 
built originally upon the gravel, the rapid advance of the hydraulic washing has made at least one 
removal necessary, and, after the recent fire, the town was rebuilt in a still different place. At 
Woolsey Flat, also, two different towns have been washed away since hydraulic mining began. 
Columbia Hill has been moved from an uncertain gravel foundation to its present site upon the 
bed-rock. The town of Omega, on the Washington ridge, has been moved once, and will have to 
be moved again, before many years, if mining continues without interruption. 
There is another class of errors, difficult to correct except at great expense. These relate to the 
positions of the mining ditches, and to the line of demarcation between the volcanic stratum and 
* Some corrections in manuscript have been made upon the copy of the map left at Cambridge. Other errors 
may as well remain uncorrected until such time as more trustworthy and detailed surveys can be made. For 
example, it is known that the section corner, last T.18N, R. 10 E.,, is a few rods only to the south of the 
hotel at Moore’s Flat, and that the section line runs just in front of the hotel door. But to make that correction 
by itself, without making any change in the position of other places in the vicinity, would introduce confusion of 
a different kind. 
