60 GEAVEL AND PLACER MINING IN ALASKA. [bull.263. 
of the first importance. No operator should contemplate the installa- 
tion of mechanical excavators for working gravel without taking full 
account of it. 
In considering methods of mining by water or mechanical power, 
the cleaning of bed rock by men may be permissible from an economic 
standpoint in exceptional instances, as, for example, where a thick 
overburden is cheaply removed by hydraulicking and a very thin rich 
pay streak remains. When, however, a mechanical method of remov- 
ing overburden and low-grade gravels costs from 50 cents to $1 & 
yard, and the whole area has to be gone over again by men to wheel 
the rich pay to the sluice, the gravel must be extraordinarily rich to* 
pay a profit. The lowest cost of handling gravel by the method of 
shoveling in was found to be $1 per cubic yard on one of the creeks 
of Seward Peninsula, while the cost may reach $5 on some of the 
isolated interior creeks of Alaska. a From 10 cents to $1 per square 
yard of area worked must be generally added to the shoveling cost to 
cover the cost of stripping muck or overburden. Ground which 
exceeds 12 feet in depth of combined stripping and pay will rarely 
pay if handled by the method of shoveling into the sluice. 
HORSE SCRAPING INTO SLUICE BOXES. 
Ground which can be worked by men shoveling into sluices can, 
under certain conditions, be worked satisfactorily by horse scraping, 
and at an expense of one-third of that necessary to shovel in. The 
most important governing condition is the degree of looseness in the 
gravel and in the underlying auriferous bed rock. Two horses, or, 
better, mules, hauling a scraper, with driver, will cost from $17 to 
$23 a day, and in the ordinary small gravel of the Alaska placers, 
with soft schist bed rock, the team will scrape into the boxes from 
30 to 40 cubic yards of gravel a day over a distance of 75 feet. On 
Penelope Creek, in Seward Peninsula, it was said that the team would 
handle as much as 10 men could shovel, the cost per cubic yard being 
30 cents. 
One common breaking plow with a team of horses suffices to break 
up enough ground for four scrapers. The method requires an inclined 
platform built up to a height of 10 to 15 feet above the bed rock, over* 
the head box of the sluice. A rectangular opening in this platform 
serves as a chute to the dump box. Generally the horses travel in 
an elliptical track, passing the end of the tail box and scraping the 
tailings from it, then entering the pit, scraping up the pay, and after- 
wards delivering it to the sluice. In Seward Peninsula the cost 
of this method can be brought as low as 25 cents per cubic yard, and 
in no part of the interior will it exceed 50 cents, exclusive of top 
stripping. 
a See cost sheet, table No. 1. 
