244 RESOURCES OF CALIFORNIA. 



Its in the wide end of another, and in that way the shiice 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 feet. 

 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 sIoav 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 Avith sledge-hammers before 

 they 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 



