26 ECONOMIC GEOLOGY. 
about ten inches wide was cut into, showing free gold, and that in re- 
spectable quantity. The vein was followed down, and, with several feet 
of the adjoining rock, proved to be highly auriferous. Mr. Hawes’s 
assay of samples selected by me showed the presence of 20 ounces of 
silver, and 2.5 ounces of gold to the ton. Trial with a pan revealed 
considerable gold before the decomposition of the pyrites, and much 
more after calcination. From $70 to $80 to the ton seemed to be a com- 
mon yield, judging by the eye. The material examined was a soft, argil- 
litic schist, full of crystals of arsenical pyrites. Massive layers of this 
same mineral an inch thick had been noticed in the quartz vein. 
After descending 25 or 30 feet, the vein and its accompanying aurifer- 
ous bands disappeared, and has never been found again, and consequently 
mining operations ceased. This opening is almost on the line of fault 
described in Volume I, page 305. The magnitude of the throw—nearly 
1,200 feet—shows that the disappearance of the vein by faulting is not 
singular; but the richness of the auriferous deposit would render it desir- 
able to search for its continuation. 
The presence of so much gold with arsenical pyrites, here and at the 
Atwood and Allen mines, has suggested to me the probability that this 
may indicate the natural affinities of the metal in this district. The for- 
mation in which the Cook and Brown mine is located is the Lyman 
group,—unlike the Dodge vein in the clay slate. Future explorers will 
do well to remember these facts, and not neglect the arsenical ores, as 
they may prove to be the best in the state. 
The mill has been abandoned, after it was discovered that the supply 
of auriferous material from this mine could not be depended upon. A 
lot of fifty tons of auriferous mispickel from Ontario was afterwards 
milled in it, apparently successfully. 
The following sketch of the Crosby process is taken from a prospectus 
issued by the company owning the mill. 
The Crosby mill contains 1 engine of 50 horse-power; 1 donkey-engine, ro horse- 
power; 1 Dodge crusher; 1 pair Cornish rolls; 3 roasting cylinders; 4 Burr mills; 
4 amalgamating tubs; 4 washing tables,—besides elevator, quicksilver strainers, etc. 
The ore is pulverized by passing through the Dodge crusher and through the Cornish 
rollers. The pulverization is however incomplete, a large part of the ore going through, 
as gravel cannot be thoroughly roasted, and must cause loss. A dry stamp-mill would 
