MECHANICS AND USEFUL ARTS. 61 



have to be satisfied with the velocity communicated to the craft, 

 which we have already stated to be of 500 tons burden. 



These results were obtained on a trip from Marseilles to La Seyne, 

 where the vessel was taken to complete its outfit. 



Upon the return trip, the vessel achieved nine knots and a quarter 

 with a gentle breeze astern, and with the same inconsiderable power 

 of 60 horses, applied to a burden of 500 tons. This more than con- 

 firmed the first anticipations. The average consumption of coal was 

 112 kilogrammes, or 240 Ibs. per hour; while for an equal speed, the 

 ordinary steam-engine would require 350 kilogrammes, or 750 Ibs. per 

 hour. 



During a trip subsequently made to Algiers, results equally flatter- 

 ing were obtained. Assailed by a storm during the voyage, the vessel 

 rolled fearfully, but the engine, feeble as it was, in proportion to the 

 tonnage of the vessel, never exhibited a moment's hesitation, nor 

 suffered a notable abatement of velocity ; notwithstanding the shocks 

 it experienced, no escape of the fluids or vapors was observed ; and 

 upon the subsidence of the gale, the propeller completed its voyage 

 without, from first to last, enjoying the aid of its sails. Frequently 

 the speed was seven knots, with the consumption of only 77 kilogram- 

 mes, or 165 pounds of coal per hour, or two tons for the whole dis- 

 tance, instead of an average of ten tons, previously consumed for the 

 same transit. It must not, however, be disguised that the use of 

 ether, owing to its inflammability, is exposed to much danger, more 

 especially on marine vessels than on shore. The vapor, indeed, is 

 heavier than air; and on land, in low places, we have always the 

 expedient of exciting a powerful current of air, which will dissipate 

 the vapor, and remedy the evil ; but on shipboard and down in the 

 hold, it is much less easy, if not quite impracticable. Ether mixed 

 with air, in the proportion of 1 to 4, is explosive, as is observed in the 

 mines. The most minute precautions, therefore, become imperative ; 

 and w r e are confidently assured that M. Du Trembley has given the 

 subject the fullest consideration. 



In regard to the practicability of the other engine, Mr Rennie, the 

 eminent English engineer, stated at the Bristol association, that he 

 had been requested to investigate the efficiency of the engine, and for 

 that purpose he made a voyage in the vessel from Marseilles to Algiers 

 and back, accompanied by his son. The steam-boiler is adapted only 

 for an engine of thirty-horse power, and during the return voyage 

 Mr. Rennie placed the coals under lock and key, so that he might 

 ascertain exactly the quantity consumed. The result of his investiga- 

 tions was, that by the additional action of the ether vapor there was 

 a saving of from 60 to 70 per cent. ; and the amount of gain had been 

 reported by a French commission, appointed to examine the engine, at 

 74 per cent. The loss of ether by leakage did not exceed in value 

 one franc per hour during the voyage, and that might be greatly 

 reduced by improved construction in the machinery. The French 

 Government have paid the inventor a very large sum for the inven- 

 tion, and there are now several ships in course of construction to be 



