466 SCIENTIFIC RECORD FOR 1882. 



a rubber capsule at the end of a nietallic tube, through which, and the 

 attached flexible tube, the resulting pulses pass to the portable signal 

 bell. The apparatus is compact and easily adjusted. {Xatio'e, January, 



1882, XXV, p. 290.) 



3. Of Gases. 



Hannay has made an extended series of experiments to obtain an 

 absolutely vacuous space and to test the hypothesis that ordinary mat- 

 ter, and not the ether, is the medium by which radiation is propagated. 

 He finds that not only is there a closely adherent layer of gas on every 

 surface, but that the gas seems, even at ordinary pressures, to penetrate 

 into or combine with the surface of the glass, and that it is with extreme 

 difQculty that even a portion of this gas is driven off, the greater por- 

 tion remaining fixed even to the softening point of the glass. In order 

 to avoid the very appreciable tension of mercury vapor, fusible metal 

 was substituted, the barometric height of which was 41 inches. Various 

 forms of Springel pump were constructed for use with this alloy, the 

 fusing point of which was 94° C. After the highest possible vacuum had 

 been attained, one of the bulbs was surrounded with calcium chloride 

 and snow, and the other interposed between a standard caudle and a 

 radiometer; but no effect was perceptible. In a mercury vacuum of 

 2yooWoo- measured by the McLeod gauge, the Holtz spark passed; but 

 when fusible metal was used it failed, even when 12 Leyden jars were used. 

 The 12-inch spark of an induction coil also failed to pass. Nevertheless, 

 such a vacuum still contained air obstinately retained by the glass. To 

 obtain a real vacuum the author proposes glass bulbs formed of hard 

 glass without and soft glass within, so that they can be heated up to the 

 softening point of the latter and preserve their shape. {Phil. Mag., April, 

 1882, y, XIII, p. 229.) 



Kraievitsch has sought to establish the hypsometric formula by direct 

 observation, and at the same time to ascertain whether gases have a 

 limit of elasticity. Two baro-manometers were used, one on the ground 

 and the other on the top of a high building, or even on the summit of 

 a neighboring hill, their manometric branches being connected by a 

 long metallic tuWe. On rarefying the air in this tube the lower instru- 

 ment will always indicate a higher pressure than the other. (J. Phys., 

 December, II, i, p. 577.) 



The same author has communicated to the Russian Physical Society 

 the results of his researches on the elasticity of air, showing that rare- 

 fied air does not obey the Boyle-Mariotte law, its elasticity diminishing 

 more rapidly than its density in proportion as it becomes more rarefied, 

 becoming equal to zero while yet the density has a measurable value. 

 It results from these experiments: first, that the earth's atmosphere is 

 limited; and second, that our weights of gases contain an error, since, 

 however perfect the pneumatic machine, it cannot pump all the air 



