G70 Transactions of the American Institute. 



dissolved substances, bnt on solid corpuscles which they hold in sus- 

 pension ; in fact, inoculation with dissolved substances remains with- 

 out result, and that with corpuscles produces characteristic results. 

 By similar experiments, M. Chauveau proves that the miasms diffused 

 in the air are not disengaged gases, but solid corpuscles. The fluid 

 obtained by condensing the vapor arising from the evaporation of a 

 virulent liquid may be used in inoculation without danger, while the 

 primitive liquid retains all its contagious properties. The same results 

 were obtained in experimenting with the virus of small-pox, the rot, 

 the epizootic typhus, etc. 



XI. Nitrate of Silver and Charcoal. 

 Prof. Chandler, editor of the American Chemist, states in that 

 journal that when solid nitrate of silver is placed upon glowing char- 

 coal deflagration takes place, the result being that silver is left behind 

 in the metallic state. The curious phenomenon attending the reac- 

 tion is that the nitrate, being fused by the heat of chemical action, 

 sinks down in the pores of the coal, and as each particle of the latter 

 is replaced by the reduced silver, the structure of the original wood is 

 retained. In this way he has succeeded in producing masses of silver 

 weighing an ounce or more, which show most beautifully the rings 

 of annual growth in the wood. The author advises that a ciystal of 

 the nitrate be placed on the end of a stick of charcoal, and the blow- 

 pipe flame directed upon the coal beside it to start the reaction. As 

 soon as the deflagration sets in, crystal after crystal may be added. 



XII. Solidifying and Melting Points of Pats. 

 Dr. Wimmel, in Poggendorff Ann., directs attention to the fact 

 that many fats may be made to solidify at two different temperatures. 

 Those fats which yield glycerine by saponification especially show 

 this peculiarity, the temperature at which solidification occurs being 

 lower than that at which melting takes place. "When these fats, after 

 melting, are allowed to cool, their temperature gradually falls to a 

 certain point, where, for a time, it remains stationary, and then exhibits 

 a certain rise as it becomes solid. The definite degree of heat at 

 which this takes place Dr. Wimmel proposes to call the natural point 

 of solidification, as this point is less changeable than the melting 

 point — a characteristic the direct opposite of that attending the 

 change of water into ice. The fact that ice is formed at different 

 temperatures, has led to the adoption of the melting point of ice as a 

 fixed point from which to measure degrees of heat. 



