1870.] CHEMISTRY AND PHYSICS. 113 



ice are produced also, from one-tenth to one-seventh part of the 

 theoretical amount, proving, thus, the remarkable fact, that in 

 both the steam engine and the ice machine, exactly the same 

 relation exists between the theoretically calculated effects and the 

 practical results. 



As, however, all the best ice machines accomplish the conversion 

 of the heat of the fuel into the freezing operation by the interven- 

 tion of a steam engine, the fact that they practically produce only 

 from one-tenth to one-seventh of the amount of the cold they 

 theoretically should produce, is solely due to the other fact, that 

 the steam engine itself practically produces only from one-tenth 

 to one-seventh of the amount of power which would be strictly 

 equivalent to the number of heat units consumed. It must not 

 be lost sight of that it is only the power of the steam engine 

 which generates the cold in the freezing machines, and that 

 therefore, improvements in the steam engine, which bring its 

 practical results nearer to the theoretical standard, will at once 

 exert their influence on the amount of ice the ice machines can 

 produce, and, consequently, also on the cost of the ice manufac- 

 tured in these machines. 



Moreover, it appears that the kind of freezing machines in 

 question, which convert power into cold, notwithstanding they are 

 yet in their infancy, have already attained such a degree of 

 excellence, that they are ahead of that class of machines which 

 convert heat into power, either by steam, hot air, or any other 

 possible means, as it is proved that they produce the full theoretical 

 equivalent of cold (negative heat) for the number of foot-pounds 

 employed ; namely, cooling one pound of water one degree for a 

 power equivalent to 700 pounds, descending one foot, which, 

 expressed in the adopted scientific manner, is one unit of negative 

 heat for every 700 foot-pounds consumed. — Scientific American. 



Pins pointed by Electricity. — A recent discovery has been 

 made by M. Cadery, telegraph inspector on the Western Swiss 

 railroad, ahd is now applied with success at Aix la Chapelle 

 (Belgium), whence needles and pins are shipped to all parts of the 

 world. On passing a metallic wire (brass, copper, iron or steel), 

 connected with the negative pole of a Bunsen's battery, through 

 the bottom of a glass tube, closed in such a way as to hold an 

 acidulated liquid, and leading the other wire of the positive pole 

 through the superior opening of the glass tube, closed in such a 



YOL. Y. G No. 1. 



