MECHANICS AND USEFUL ARTS. 99 



emy. It was thought by some officers that the explosion would 

 throw the earth up on either side in such a manner as to form a 

 trench ; but the result was not so ; the earth was thrown up in a 

 mass, and no trench was formed in which men could get under 

 cover at once. The experiments were of great interest and 

 highly satisfactory. Van. Nos. Eng. Mag. 



COMPARISON OF NATURAL AND ARTIFICIAL ICE. 



The French company Messageries imptriales, wishing to ascer- 

 tain what kind of ice would be preferable for their vessels navi- 

 gating the Suez Canal, caused experiments to be made, under 

 identical circumstances, with several varieties, with the following 

 results : Time required to melt 200 pounds of ice : 



Natural ice of Switzerland, 107 hours. 



" " Norway, 115 " 



" " Massachusetts, 138 " 



Artificial ice, Carre's machine, , 130 " 



" " Tellier's machine, 144 " 



If these experiments were conducted with accuracy, they would 

 seem to prove that artificial ice would have the preference over 

 the natural production of our lakes and rivers for transportation 

 on shipboard, and for refrigerating mixtures. One series of ex- 

 periments is scarcely sufficient to settle a question of this impor- 

 tance. 



THE TELLIER ICE-MACHINE. 



The manufacture of ice by artificial processes is steadily gaining 

 ground and favor. During the last summer it has received a 

 powerful impulse from the exorbitant prices asked and un- 

 willingly paid for ice in this and southern cities, in which this 

 article has become so much a necessity that people will pay 

 almost any price rather than be deprived of it. In this city its 

 price reached 2 cents per pound before the close of summer, and 

 in one southern city, we are informed by a correspondent, it 

 reached 5 cents per pound. 



It is not probable that such exceptionable prices can be main- 

 tained during ensuing seasons; but even at the prices at which 

 we may reasonably hope to purchase ice, or at least such prices 

 as must be demanded for ice shipped to southern towns, it is now 

 demonstrated it can be produced artificially at large profits and in 

 any required quantity. 



Two machines have been brought prominently into public 

 notice, each employing the same volatile material as an absorb- 

 ent, conveyer, and radiator of heat, and being in some sort 

 rivals in the effort to secure public favor. We allude to those 

 known as the Carre and the Tellier ice-machines. The volatile 

 agent in both is generally ammonia, and, though differing widely 



