Chemistry and Physics. 307 
entirely frozen mass contained 0°59 cubic inch of air in each 
pound weight. (3) The freezing of a limited body of water 
which had first been frozen over and the surface ice removed, 
points still more strikingly to the concentration of air in solution ; 
for this contained 0°89 cubic inch of air in each pound weight, 
compared with 0°15 cubic inch in surface ice, and 0°59 cubic 
inch in an entirely frozen mass.—WVature, Feb. 3, 1887, p. 325. 
TAT 
7. Transmission of Electricity of feeble tension by hot air.— 
In 1853, M. Ed. Becquerel discovered that gases of a high 
temperature became conductors of electricity even of feeble 
electromotive force. M. Bronpuor has confirmed the results of 
Becquerel. With an electromotive force of 75> of a Volt, the 
transfer of electricity took place when the gas or air attained the 
temperature of red heat. Ohm’s law does not seem to be fulfilled 
by this phenomenon. Hot air has not electrical resistance properly 
so-called. The author believes that the mechanism of the trans- 
mission of electricity in this case is due to what Faraday termed 
convection of electricity. — Comptes Rendus, No. 5, Jan. 31, 1887, 
p. 283. J.T. 
8. Aperiodic Electrometers.—M. Ledeboer brings the needle 
of a quadrant electrometer quickly to rest by making the quad- 
rants of steel highly magnetized. The movement of the needle 
produces currents of induction and is dampened thereby. The 
suspension is unifilar.— ature, Feb. 3, 1887, p. 331. J.T. 
9. Harth Currents.—At a meeting of the Physical Society 
held in Berlin, Dec. 3, 1886, Dr. WrINSTEIN gave some of the 
results of his observations on earth currents on the telegraph 
lines of the German Empire. The earth’s currents showed a 
daily period with eight fluctuations, which did not occur through 
the whole year and were not constant in direction. These fluctu- 
ations were least in the morning between five and seven o’clock. 
The earth’s current showed an intimate relation to the earth’s 
magnetism and especially to the declination. The author found 
no relation between the earth’s current and the sun’s rotation, 
and also doubted the relation supposed to exist between the 
earth current and the earth’s magnetism.— ature, Feb. 3, 1887, 
p. 336, J.T. 
10. Photography by Phosphorescence.—In a recent number of 
the Scientific American, Dr. John Vansant gives an account of 
some experiments by him in taking photographs by the light 
radiated from a phosphorescent surface. A piece of paper coated 
with calcium sulphide and covered by a plate in which several 
letters were cut out, was exposed to the sunlight for two minutes. 
The light from the phosphorescent surface was sufticiently strong 
to make an image of the letters on a sheet of sensitive paper, 
developed in the usual way. A similar experiment with a photo- 
graphic negative, placed upon a sheet of glass covered with the 
calcium sulphide which had been exposed to the sun several 
minutes, gave on the sensitive paper a good positive picture of 
