PUMngton.] GENERAL STATEMENT OF CONDITIONS. 25 
To what distance and height above the collar of shaft does it transport the gravel? 
Capacity of the plant. 
Cost per cubic yard of mining, hoisting, and washing. 
What area of ground is worked from one shaft? 
If winter dumps are taken out and washed in spring — 
Size of dump. 
Method of sluicing. 
Cost of sluicing. 
Is dump rethawed? 
Method and cost of rethawing. 
Method of sampling dump, if any. 
ACKNOWLEDGMENTS. 
Acknowledgments for assistance rendered and courtesies extended 
to the party would, if made in detail, fill a volume of themselves. I 
especially extend thanks to the operators of the Atlin and Klondike 
districts, and to the officers of the British Columbia and Yukon Terri- 
tory administration for their hospitable reception to a foreign expedi- 
tion. To the citizens of Alaska, in whatever capacity they may be 
employed, the party is indebted for uniform courtesy and assistance 
as well as unstinted hospitality. Without the cooperation of the 
miners the work attempted would have been impossible. I also wish 
to express my thanks to members of the Geological Survey who have 
furnished me with the valuable results of their Alaska investigations. 
I wish to acknowledge indebtedness for assistance in preparing the 
description of ditch construction in Seward Peninsula to Messrs. G. 
A. R. Lewington, J. W. Davidson, A. H. More, and William West, 
of Nome. 
Thanks are due to Mr. J. P. Hutchins, a gold-dredging engineer of 
long experience, who has contributed to the report an authoritative 
treatise on that subject. 
The writer is indebted to Mr. Henry C. Perkins, of Washington, 
for many suggestions made during the final preparation of the manu- 
script, especially of that portion dealing with hydraulic mining. 
GENERAL STATEMENT OF CONDITIONS. 
Placer mining is that form of mining in which the surficial detritus 
is washed for gold or other valuable minerals. When water under 
pressure is employed to break down the gravel, the term hydraulic 
mining is generally employed. There are deposits of detrital mate- 
rial containing gold which lie too deep to be profitably extracted by 
surface mining, and which must be worked by drifting beneath the 
overlying barren material. To the operations necessary to extract 
such auriferous material the term drift mining is applied. 
As nearly all mining in alluvial deposits comes under the head of 
gravel mining, that term has been adopted in the main for operations 
ijdescribed in the report of which the following chapter is a summary. 
