hi GENERAL SUMMARY OF SCIENTIFIC AND 



tional experiments upon salt solutions and attached water, 

 lie assigns the name cryogen to an appliance for obtaining a 

 temperature below C, and cryohydrate to the substance 

 produced by the union of water with a body, this hydrate 

 being capable of existence only below C. He finds that 

 of cryogens the best is a mixture of sodium bromide with 

 three to six times its weight of ice finely divided, the tem- 

 perature produced being 28 C. From an extended series 

 of experiments, he concludes that " of similar salts, the one 

 which produces the greatest cold when used in a freezing 

 mixture unites as a cryohydrate with the fewest molecules 

 of water." And again, " The temperature at which the cry- 

 ohydrate is formed is the same as the temperature of the 

 corresponding freezing mixture." Of special interest is the 

 cryohydrate of ethyl alcohol, which is produced whenever a 

 dilute alcohol is exposed to a temperature of 34 C, and 

 has four water molecules united to one of alcohol. It sepa- 

 rates from the liquid in crystals. Ether also forms a cryo- 

 hydrate, solidifying at 2 C, and consisting of one ninth of 

 ether. If the experiment be made in a long test-tube, the 

 long candle-like mass, when removed, placed upright on a 

 plate, and lighted, burns with a non-luminous flame, the heat 

 bein<x consumed in meltinq; the ice. 



Chaumont has experimentally investigated the question 

 of ventilation, so far, at least, as the amount of air necessary 

 for health is concerned. His determinations were made on 

 the air of barracks, of prisons, and of hospitals; and he con- 

 cludes from them that 85 cubic meters (3000 cubic feet) of 

 air per head per hour is necessary in health, in ordinary dis- 

 eases one third more than this, and in serious diseases and 

 epidemics even more still. 



Gernez has made an exhaustive research into the phenom- 

 ena attending ebullition. His paper opens with a long his- 

 torical note upon this subject. Then follows his own results, 

 in which he studied (1) liquids heated in contact with solids, 

 (2) within other liquids, and (3) the ebullition developed by 

 mechanical action. He maintains that ebullition is an evap- 

 oration into some gaseous atmosphere contained within the 

 liquid. 



Troost and Ilautefeuille have made a calorimetrical inves- 

 tigation on iron and manganese silicides. They conclude, 



