— and Geol. 267, . 
with it. Moreover the para iil does not state that the “ conelu- 
shen, ” as rewer says, “but that the conclusion was _ ained, 
and this single conclusion is pope in full, so that there i 0 possi- 
bility of mistaking which one of Sir R. L Murchison’s conclisions 
was intended by me. The following: is the paragra 
seer ing: very modern ; that it is one of the of gold is geclog formed - 
metals; the rocks being probably impregnated with it after the 
Miocene period, and but a short time before the epoch when the 
powerful and. general denudations took place which destroyed the 
large extinct mamm 
Thi is paragraph follows a description of the various forms of 
auriferous drift, and no reference whatever is made to the Silurian - 
or Devonian age of the rocks. 
The other statement, given in my preface, of the probability of 
the presence of Silurian formations, when fully quoted, as in the 
encement of this article, bears internal evidende: of the in- 
justice of this imputation b Prof, _ Brewer. A full eeay ots of 
ery of Silurian pet sem - fr silver and ees region of Neve 
Seed any other point than the raving in respect to the Garner 
aap 0h of = eed _ the gol; 
Haven 
6. Mem 
vol. i, pa rt IE ¢ Principles of the 1 Matveral System KA Voloanie 
F. Baron RicnrHoren.” 95 pp. 4to. San Francisco, 
s—athe wg classifies voleanic rocks in the following orders 
SOebere first: RayoultE ; fam. 1, Nevadite ; 2, Liparite ; 3, 
Rhyolit 
Cviben doth -dedcinits : TRACHYTE; fam. 1, Sanidin trachyte; 2, Oligo- 
oat Wanna 
* Report Geological Reconnoissance in California, pp. 278-9. ¢ Siluria. | 
