DREDGING FOR GOLD.

The many varying conditions under which gold is found is not the least interesting feature of the history of the yellow metal. In rock, sand, and sea it has been discovered, and even in the deposit of hot springs now in activity. Large nuggets have been discovered in dry gravels, while prospectors have acquired much wealth by extracting gold from river beds, by the process known as panning—i. e., separating the dirt and mud from the metal by shaking the gold-bearing earth or gravel with water in a pan.

While, however, many rivers have been thus exploited, explorers and scientists are agreed that there are still millions of dollars' worth of gold waiting to be unearthed from the bottom of rivers in different parts of the world. In New Zealand and South America, for instance, convincing proof has been obtained that rich deposits of the precious metal still lie at the bottom of many of the rivers of those countries. The gold is usually found in the form of grains at some depth below the surface, imbedded in mud and clay.

There are only two ways of recovering it—namely, either the river bed must be dredged by floating dredgers, or the river must be diverted into another channel while its bed is being stripped. The former method is the one generally adopted, dredgers having been used with considerable success on the Pacific Slope.

Attention has been attracted of late years to the possibilities of recovering gold from the rivers of Peru. For ages the gold-laden quartz of the land of the Incas—the people who covered the walls of their temples with plates of gold and used the precious metal to fashion cooking utensils—has been broken down by the denuding agencies of frost, rain, and snow, and carried into rivers, where it has remained undiscovered, until recent explorations revealed an astonishing source of wealth.

Take the River Inambari and its tributaries, for instance. An examination of 30 miles of this river revealed the fact that it contained gold to the average value of $1.75 per cubic yard, which could be extracted at a cost of 12 cents only. The result of this examination led to the formation of the Inambari Gold Dredging Concessions, Limited.

Sir Martin Conway some time ago explored upper Peru and the famous gold-producing valleys from which the Incas gained most of their great store of wealth. He came to the conclusion that in a certain area no less than $10,000,000 profit was to be made by extracting gold from the rivers, and in order to begin obtaining this gold it was only necessary to have a dredge on the spot. The same hour in which the dredge first begins to turn, gold will be won.

The dredges used up to the present have been almost exclusively of the endless-chain bucket or steam-shovel pattern. At one end of the boat is a powerful endless-chain bucket-dredge, which scrapes the gravel from the bottom and elevates it to a revolving screen in the boat. This in turn sifts out the bowlders, which are at once thrown to the bank of the river, while the fine material flows over tables covered with cocoanut matting, which acts like fine riffles, catching the gold in the interstices. The matting is periodically lifted up and thoroughly rinsed off, the rinsings are panned for gold, and the matting returned for another charge.

In the case of the Inambari Gold Dredging Company, a modern steel dredger has been made, which it is confidently estimated will work far quicker and in a much more effective and inexpensive manner than any other dredger which has yet been used.