758 Transactions of the American Institute. 



would be very desirable for building in other places. In that case 

 very little cohesive strength was required. 



"We should make a broad distinction between inventions demon- 

 strated to be of practical utility, and mere theories. As I understand 

 it, this selenitic mortar is only a scheme propounded by somebody, 

 backed by a few petty experiments, and therefore does not stand in a 

 position to be received as an addition to our knowledge. 



The President — It is read only for the purpose of inducing any 

 one, having the opportunity, to test its merits. 



IV. Electromotive Force of Induction. 

 Dr. L. Hermann has given, in PoggendorfPs Annalen, the results 

 of a series of experiments undertaken by him for the purpose of 

 ascertaining whether the electromotive force of induction, demon- 

 strated by Faraday in liquid conductors, was the same as that in 

 metallic ones, other conditions being the same. Since in the latter 

 instance the inducing force is independent of the nature of the metal, 

 the question arises, does this independence of the nature of the 

 induced conductor also extend to liquids, and therefore to all conduc- 

 tors ? Dr. Hermann made three experiments with three different 

 arrangements, all with the same result. He describes the most 

 successful in detail ; and then adds, these experiments show with 

 certainty, since the resistance in the induced circuit in all cases is the 

 same, that the electromotive force of the induced current is, in the 

 widest sense of the word, entirely independent of the nature of the 

 induced conductor. 



Y. To Prevent Spontaneous Explosion. 

 Dr. Zaliwski, in a recent memoir, states that the explosive property 

 of some inflammable substances depends upon the hygrometric condi- 

 tion of the atmosphere ; that gunpowder and other explosive mate- 

 rials may become spontaneously explosive, even without any eleva- 

 tion of temperature of the air, but that the smallest quantity of oxalic 

 acid mixed with such explosive material will prevent spontaneous 

 action. He further states that this fact may be experimentally proved 

 by adding to any explosive mixture — sulphur and chlorate of potash, 

 for example — a certain quantity of oxalic acid, after which the mix- 

 ture can be heated to the point of fusion without exploding. A fair 

 inference seems to be that the treatment suggested by Dr. Zaliwski 

 actually impairs that property in explosives on which their value 

 depends. 



