Book Name Hydraulic Mining in California Author Bowie published 1885

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Bowie Hydraulic Mining in California

Bowie Augustus Jesse published a book named 'A Practical Treatise on Hydraulic Mining in California' focusing on gold mines and mining in California.

The Distribution Of Gold In Sluices

In cleaning up sluices the largest portion (approximat­ing 80 per cent.) of the gold caught is found in the first 200 feet. The gross yield of the Gardner's Point claim for the season of 1874 was $63,000 for 100 days' run. Of this amount $54,000 were obtained in the first 150 feet, and $3,000 were taken from the undercurrents. The re­mainder was found lower down along the sluices. The first undercurrent was 790 feet distant from the head of the sluice, and yielded 50 per cent, of the total yield of the undercurrents. The second undercurrent was 78 feet dis­tant from the first, with a drop of 40 feet between them, and it contained 33 per cent, of the gross undercurrent yield. The third undercurrent was 91 feet distant from the second, with a drop of 50 feet between them. Its yield was nearly $500.

It sometimes happens that a hundred or a hundred and fifty feet at the head of a sluice are covered with gravel during the greater part of a run. In such cases the gold is found farther down. In the North Bloomfield tunnel the upper 300 feet of the sluice are generally filled from one to five feet deep with gravel, and still this por­tion yields much more amalgam per linear foot than the succeeding 300 feet of sluice.