Popular Science Monthly 



851 



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 tiie 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. 



