MECHANICS AND USEFUL ARTS. 61 



M. de Lesseps, the Suez Canal engineer, having sent some 

 surveyors to examine the desert of Sahara, has, it is said, become 

 convinced that the desert is at its nearest hmit 27 metres below 

 the level of the Red Sea, and that the depression continues in- 

 creasing toward the interior. He therefore thinks that he can 

 make the desert the bed of a large inland sea, by a canal of 75 

 miles in length, bringing the water from the Red Sea. Besides 

 climatic changes, an easy method of intercourse with Central 

 Africa would be effected if this project could be accomplished. 



Mr. Lange, the London representative of the Suez Canal Com- 

 pany, has made some experiments on the canal with a corvette 

 carrying ten Armstrong guns, and driven by engines of 300 horse- 

 power. He has ascertained the following important points : 

 First, the speed necessary to be maintained on a vessel of the 

 dimensions of the ship experimented with, in order to enable 

 a straight course to be steered, is from 3.2 to 3.7 knots an hour. 

 Second, the embankments suffered no injury while the vessel was 

 going at a rate of 5.4 or 6.4 knots an hour. Third, it was found 

 that the loss of speed incurred by the vessel navigating the canal 

 when compared with the rate on the open sea in smooth water, 

 amounted to one-fourth, the same power being employed in both 

 cases. 



STEAM POWER ON CANALS. 



A successful application of the principle of low speeds seems 

 to have been made by Mr. Edvvard Backus, of Rochester. If the 

 result of the several trials made are correctly stated by the in- 

 ventor of this novel mode of steam propulsion, then the cost of 

 transportation may be reduced about 32 per cent. 



The following extract from a letter written by Gen. Quimby, 

 U.S.A., who witnessed two trials of this boat, will convey an 

 idea of the character of this new mode of propulsion : — 



" In this boat the motive power, steam, causes a wheel located 

 near the centre of the boat to roll on the bottom of the canal, and 

 thus drive the boat in the same manner that the locomotive is pro- 

 pelled by its driving-wheels. The wheel, placed at one end of a 

 lever frame, readily adjusts itself to the varying depths of the 

 water, and its weight, together with the cog-like projections dis- 

 tributed over its circumference, prevents slipping and consequent 

 loss of traction. It has been found that in the whole extent of the 

 Erie Canal there are not to exceed 20 miles in which the 

 depth of tlie water is too great for the wheel to work well. For 

 very deep water, a screw-proi3eller wheel is used, and the motive 

 power is changed from the ground wheel to it with the utmost 

 ease and expedition." 



PASSAGE THROUGH THE SUEZ CANAL. 



The Rob Roy and English merchant-vessel recently passed 

 through the Suez Canal, and the captain writes to the ♦• London 

 Times" the following account of the present condition of this great 

 undertaking, after 13 years have been spent in its construction ; 



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