PHYSICS. 227 



emy, and appointed professor in the Ecole Polytechnique. 

 In 1841 be was made Professor of Physics in the College 

 de France. His removal to Paris changed the character of 

 his investigations. First he made his celebrated research on 

 specific heat, in the course of which he invented the air-ther- 

 mometer in its present form ; then he studied the phenome- 

 na of expansion, vapor tension, and hygrometry. In 1854 he 

 was made Director of the Sevres Porcelain Manufactory, and 

 improved considerably the ceramic art at that place. The 

 death of his son Henri, an artist of promise, on the battle- 

 field during the Prussian war, depressed him exceedingly; 

 and on his return to Sevres after peace had been declared, 

 the discovery that the results of his last great research on 

 the heat phenomena accompanying gaseous expansion, drawn 

 from over 600 observations, had been destroyed, seemed to 

 shatter still more his nearly exhausted frame. He never re- 

 covered from these shocks, but died on the day that the ar- 

 tists of Paris were laying their wreaths upon the grave of 



his son. 



1. Thermometry and Change of State. 



Negretta and Zambra have contrived a new deep-sea ther- 

 mometer, described and figured in Nature. To a cylindrical 

 bulb containing mercury a tube is fitted, which is contorted 

 and constricted near the bulb, and is enlarged at the remote 

 end, from which end it is graduated. When the bulb is held 

 downward, the mercury expands as usual, but when it is re- 

 versed, the column breaks at the narrowed portion of the 

 tube, flows to the other end of this, and is there read. Hence, 

 if the thermometer be lowered with the bulb downward, 

 and reversed on attaining the desired depth, the reading on 

 coming to the surface will represent the temperature at the 

 time of reversal. To prevent the errors caused by pressure, 

 it is enclosed in a glass sheath. 



Himly has proposed to observe melting-points electrically 

 by coating the bulb of a thermometer with silver to make it 

 a conductor, which is then thickened with copper deposited 

 electrolytically. The bulb is coated with the substance 

 whose fusing-point is to be determined, and, when cold, is 

 placed in mercury, which is in the circuit of a battery and 

 electric bell. When the mercury is heated to the tempera- 

 ture at which the substance melts, the metallic contact is 



