Page:Charleston • Irwin Faris • (1941).pdf/203

 Gully, and at the back of Little Beach; the latter worked by Mouat & Harper.

What was the origin of these leads? Well, gold is not fed into the middle of a river but is brought into it by some side-stream, or is washed out of the gravels forming the riverbanks, and is thrown on to the beaches at either side. When gold settles on a line of beach or shelving bank, it forms a “lead” of pay-wash. Similar leads are formed along ocean beaches by the tide. Countless ages ago Nature worked in the the same way as to-day, and some of the leads and gravels, and the beaches formed then and since, are the goldfields of our day.

The old deposits were preserved: (a) Usually because a protective covering of later sandstones or clays or gravels was laid above them; or by the channels being filled up. (b) Because the ocean beach was sinking and its lead being constantly covered with more and more sand, thus protecting the “beach lead.” (c) Because, but more rarely, the lead was part of a tract affected by faulting, and it and its surroundings dropped some hundreds of feet and were covered with later deposits. The leads of former ages, preserved in some manner such as in (a), (b), or (c), are the deep leads of our times, the protected covers of which vary from a few feet to hundreds of feet in thickness; and above the first protecting cover may be more recent leads having no connection with the deeper ones. The West Coast leads were formed mainly as in (a) and (b).

All Charleston workings were surface-workings, none being underground mines, though there were short drives on the deeper leads, and a few hydraulic elevators. At Charleston the black-sand layers are overlain by marine material only, and the cover does not usually exceed 10 or 15 feet. At least six of these layers lie from 450 to 600 feet above sea level, and are locally called “500 foot levels.”

Much of the Charleston gold was coated with an oxide of iron, making the process of amalgamation difficult. This was termed “rusty gold,” and tables using copper plates for catchments secured only a small proportion. The loss thus sustained was proved by the Dublin City Company which sent five tons of cement to Melbourne to be treated by the “chlorine