liv GENERAL SUMMARY OF SCIENTIFIC AND 



cone of platinum, having on each side of its base a j)latiniim wire 

 leading to the batteiy. The crj^stal plate is previously covered with 

 some easily fusible substance (the author prefers lard), the little cone 

 is brought upon its centre, and the circular or elliptical form of the 

 liquefied portion of the covering material becomes very soon appar- 

 ent. By this means Jannetaz has obtained some very curious re- 

 sults. 



Maumen^ has communicated to the French Academy the results 

 of his experiments on the temperature produced by mixing together 

 olive-oil and concentrated sulphuric acid, in which he calls attention 

 to the remarkable fact that the evolution of heat is greater if tlie 

 acid has, just before use, been heated to ebullition. The same fact 

 is true, he thinks, of other bodies having a high boiling-point. Such 

 bodies by thus being heated suffer no proper chemical alteration, 

 but undergo, apparently, a change in molecular structure, the evi- 

 dence of w hich is a variation in the number of calories produced 

 in their chemical actions. For example, fifty grammes of olive-oil 

 mixed with ten cubic centimeters of acid recently boiled produce a 

 rise of temperature of 42. Using a specimen of acid two months 

 old, of specific gravity 1.845, the rise was only 34.5 ; the same acid 

 freshly distilled gave a rise of 44. 



Witz has experimented successfully with the freezing mixture sug- 

 gested by Pierre and Puchot, i. e., a mixture of hydrochloric acid 

 and snow. He finds, for example, that 250 grammes of fine snow at 

 zero mixed at once with 250 grammes of hydrochloric acid (com- 

 mercial) of specific gravity 1.1823, at 1, give in the course of one 

 minute a solution having a temperature of 37.5. If the acid be 

 cooled previously to 18, the mixture produces a cold sufiicient to 

 freeze mercury very readily. 



Page has described a simple form of gas regulator, which has the 

 especial advantage that it is not affected by variations in the baro- 

 metric pressure. It consists of a mercurial thermometer, the stem 

 of which is three sixteenths of an inch in inside diameter and open 

 at the top. The gas is admitted through a fine tube which is 

 placed within the thermometer tube, so that the rise of the mercury 

 within this cuts off the supply of gas when the desired temperature 

 is exceeded. This regulator kept a beaker of water for four or five 

 hours within a range of 0,2 Centigrade, and kept the temperature 

 of an incubator for six weeks within 0,5 Centio-rade. 



The intimate relation between the diffusion, the viscosity, and the 

 conductibility of a gas on the mechanical theory of heat renders in- 

 teresting some careful experiments of Kundt and Warburg upon the 

 last two properties of gases above given. The results obtained give 

 for the friction coefiicient of air at 15 the number 0.000189, for hy- 

 drogen 0.0000923, and for carbon dioxide 0,000152. The value ob- 

 tained for aqueous vapor was 0,0000975, The correspondence be- 



