O44 RESOURCES OF CALIFORNIA. 
fits in the wide end of another, and in that way the sluice is 
put together, a long succession of boxes, the lower end: of 
each resting in the upper end of another, and not fastened 
together otherwise. These boxes stand upon trestles, with a 
descent varying from eight to eighteen inches in twelve fect. 
It is therefore an easy matter to put up or take down a sluice 
after the boxes are made, and it is not uncommon for the 
miners to haul their boxes from one claim to another. The 
descent of a sluice is usually the same throughout its length, 
and is called its “grade.” If there be a fall of eight inches 
in twelve feet, the sluice has an “ eight-inch grade,” and if the 
fall be twice as great, it is a ‘‘ sixteen-inch grade.” The grade 
depends upon the character of the pay-dirt, the length of the 
sluice, and its position. The steeper the descent, the more 
rapidly the dirt is dissolved, but the greater the danger also 
that the fine particles of gold will be carried away by the 
water. The tougher the dirt, that is, the greater its resistance 
to the dissolving power of the water, the steeper, other things 
being equal, should be the sluice. A slow current does not. 
dissolve tough clay, and that is the greater part of the pay- 
dirt, so rapidly as a swift one. The shorter the sluice, other 
things being equal, the smaller the grade should be. There is 
more danger that the fine particles of gold will be lost by a 
‘short sluice than by a longer one, and to diminish this danger, 
the rapidity of the current must be reduced by a small grade. 
The greater the amount of dirt to be washed, other things 
being equal, the steeper should be the grade; for a swift cur- 
rent will wash more dirt than a slow one. In many claims 
the pay-dirt is full of large stones and boulders, weighing from 
one hundred to five hundred pounds each, all of which must be 
carried away through the sluice. Some are sent down whole, 
and others are broken into pieces with sledge-hammers before 
tuey are thrown into the box. These require a swift current 
and a large body of water. The larger the supply of water, 
the steeper the sluice is made, other things being equal. Of 
course economy and convenience of working require that the 
