360 RECORD OF SCIENCE FOR 1886. 



just beiow the enlarged space at the end of the tube, that part of the 

 mercury above the flame was broken off and driven into the space, where 

 it remained as the thermometer cooled. In this way the same part of 

 the scale could be used for different readings. The relative value of a 

 scale division was affected inappreciably while the absolute value 

 could be obtained by a single comparison with a standard. Further 

 improvements in calorimetry the author thinks lie in improved methods. 

 (Nature, Feb., 1886, xxxiii, 405; Phil. Mag., April, 1880, V, xxi, 324.) 

 The ice melted in the calorimeter of Bunsen is estimated in one of two 

 ways : Either by reading, on a graduated scale attached to the capillary 

 tube in which the extremity of the mercury column moves, the amount 

 of displacement; or by weighing the mercury drawn into the apparatus 

 during the melting. For this purpose a tube twice recurved and drawn 

 out like that of a weight thermometer, to a fine i)oint, dips into a vessel 

 of mercury, and is weighed before and after the experiment. Blumcke 

 has proposed to combine the two methods and to use the divided scale 

 to determine the changes in the calorimeter before and after the experi- 

 ment, while the weighing method is reserved for the experiment itself. 

 Taps placed at the terminations of the bent tube and the capillary tube 

 permit communication to be established at the proper time between 

 either of these tubes and the calorimeter. (Weid. Ann., xxvi, 159; J. 

 Phys., November, 1886, II, v, 494.) 



LIGHT. 



1. Production and Velocity. 



Auer has invented a lamp in which a cylinder of porous magnesia is 

 hung in a Bunsen llame. The burner of the lamp is surrounded by an 

 ordinary cylindrical chimney, and in the flame is hung a hollow cylinder 

 of thin organtine impregnated with the magnesia solution. The heat 

 of the flame destroys the organic matter and leaves the white magne- 

 sium oxide in the form of an elastic porous cylinder, which becomes 

 highly incandescent. The lamp is said to give a light of twenty candles 

 with a consumption per hour of 56 liters of gas. (Science, March, 1886, 

 VII, 282.) 



Ghase has called attention to the fact that Herschel's high estimate 

 of the elasticity, or as he called it the "bursting power," of the tether, 

 is not that of the simple aitherial elasticity itself, as has been assumed 

 by Wood and others, but is that which is represented by the ratio of 

 the elasticity to the density ; /. e., is that which would be exerted if the 

 air and the fether were reduced to the same density. If we substitute 

 in Herschel's proportion, the true density-ratio, we obtain 1,636,750 as 

 the ratio of the elasticity of air to that of the tether. This represents 

 an aitherial elasticity or "bursting power" of about -gg^g ounce on each 

 sideofacubic inch instead of "upwards of seventeen billions ofpounds". 



