60 ANNUAL OF SCIENTIFIC DISCOVERY. 



between the tubes, for the circulation of water and steam, was in 

 many boilers much too small ; that the clearance should be in propor- 

 tion to the number of tubes, and that for good practice, a clearance 

 at the rate of one-eighth of an inch for every thirty tubes should be 

 allowed. 



DU TEEMBLEY'S VAPOR ENGINE. 



During the past season, several practical experiments have been 

 made in France, by M. Du Trembley, for the purpose of testing his 

 new vapor engine, which has now been for several years before the 

 public. His motive power, as is well-known, is derived from the ex- 

 pansion of the vapors of sulphuric ether and of water, and the 

 engine, which is similar in all its appointments to a double-cylinder 

 steam engine, is driven by the combined vapors, which act singly, 

 each in its own cylinder, and without any intermixture. 



The condensation of the aqueous vapor is accomplished by the 

 evaporation of sulphuric ether, and the condensation of the latter, by 

 means of a current of sea-water, which constantly laves and cools the 

 surfaces of a condenser, into which the vapor passes after its escape 

 from the cylinder. These two condensations take place in close ves- 

 sels, and the exhaust-pumps return the liquids each into its proper 

 generator, so that they are alternately evaporated and condensed. If 

 it were possible to make such accurate adjustments as to prevent any 

 escape, one supply of the two fluids would serve indefinitely. To ob- 

 tain this perfection of adjustment seemed to be required by the nature 

 of things, and to this point the inventor has devoted his attention 

 mainly. Every one knows how extremely volatile ether is, and how 

 penetrating its vapor. So successful has M. Du Trembley been, that 

 in the engine room one can scarcely detect the presence of ether, not- 

 withstanding the considerable quantity which is supplied to the cylin- 

 der by the generating apparatus. 



The following details of the experiments are taken from a recent 

 French publication : 



As soon as Du Trembley considered his machine in good working 

 order, he placed it at first on a screw propeller, engaged statedly in 

 traffic between Marseilles and Algiers. The vessel was of 500 tons 

 burden. 



In the first experiments, the vacuum obtained in the condensers 

 was 62 centimetres for the aqueous vapor, and 23 centimetres for the 

 vapor of ether ; the pressure of the two vapors was two atmospheres 

 for the vapor of water, and 2 1-5 for that of ether ; the cylinder of 

 the former was 65 centimetres in diameter, and of the latter, 80 cen- 

 timetres ; their stoke of 75 centimetres. The two vapors were introduced 

 only during the half of this stroke. The number of revolutions obtained 

 witli a light breeze ahead, was from 36 to 38, which gave from 72 to 76 

 turns to the srriMv, and a speed of six knots to the vessel ; but if it is duly 

 observed that the force developed by the machine has been calculated 

 at no more than 60 horse power, it will be seen what entire reason we 



