Page:Popular Science Monthly Volume 88.djvu/879

 Popular Science Monthly

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��These Desert Mates Never Quarrel

OVER one of the trails of the Sahara Desert the queerest of teams is em- ployed in drawing a two- wheeled cart, which carries light freight. The team consists of a camel and a small mule, and while the loads may be unevenly distributed between them, the mates never disagree. Naturally, they are rarely in step. Each draws his portion of the load in his pecu'iar way, the camel loping along with great strides while the mule trots scampers — beside him.

���This Gold Dredge Is a Glutton

FROM the farm lands of Ohio has come an application for patent to Washington — and it has been granted — upon a placer-mining dredge which can wash and extract the gold from six hundred to twelve hundred cubic yards of ore dirt in a day. Moreover, an active application of the principle con- tained in the patent is doing its work daily in the placer fields of Colorado.

The action of the mining machine is not entirely unlike the well-known gold-

��The widely differing peculiarities of a mule and a camel are here combined to form a curious team

—almost dredge, or "gold hog," as it is familiarly called in California and Alaska. This machine, however, runs on tracks instead of in the water and shovels the dirt from behind instead of from in front. A capable steam dredge digs up the pay dirt, swings it above the separating machinery and drops it into a hopper. Water is sprayed on the incoming dirt at the rate of two thousand gallons a minute. The loosened ore then under- goes amalgamation (dissolving in mer- cury), the precious mass dropping below the hopper into a tank in which it is heated, the mercury being vaporized and re-condensed, and the gold accumu- lating in the tank. _____

���The dredge gulps from six to twelve hundred cubic yards of gold-laden dirt every day

��Two New Colossal Bridges

NOTABLE among the great engineering feats of the year 191 5, are the colossal bridges which were constructed. As successor to the unfinished structure over the St. Lawrence at Quebec, which collapsed a few years ago, a new bridge, the longest arch in the world, is being completed. Its span is 1800 ft. During six months of last year about 32,000 tons of steel were placed in this bridge. The beautiful arch over Hell (iate, 077 ft. long, is of massive construction for carrying great weight.

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