PHYSICS. 367 



peraturc varied from 5° to 16° C, and the result of twenty measurerQeuts 

 gave for the differeuce in the auj;le of deviation 5.06" ±0.13. From 

 this the value 0.0000202 was obtained as the coefficient of expansion of 

 the grating. {Am. J. ScL, March, 1881, III, xxi, 230.) 



Crookes has communicated a paper to the lioyal Society on discon- 

 tinuous phosphorescent spectra in high vacua, iu which he gives the 

 results of spectroscopic examination of the light from substances which 

 have been made to emit light in the highly exhausted space with- 

 in his tubes. Precii)itated pure alumina phosphoresces of a rich crimson, 

 which gives the same spectrum as that given by ruby, containing a 

 brilliant and sharp red line of wave-length G89. 5 millionths of a milli- 

 meter. The same effect is produced hy sunlight. Ignited aluminum 

 acetate gave a green, corundum a pink, sapphire alternate red and green 

 bands, spinel red, spodumeue golden yellow, glucina blue, zircouia pale 

 bluish-green, erbia, yellowish, magnesia pink, barium hydrate orange- 

 yellow, strontium hydrate deep-blue, lime orange-yellow, calcite straw- 

 yellow, diamond pale yellowish- green. Certain anomalous results ob- 

 tained in this way lead the author to believe that he has here to deal 

 with several new elements. {Nature, May, 1881, xxiv, 89.) 



Liveing and Dewar have continued their researches upon the reversal 

 of the lines of metallic vapors, and have now given their results upon 

 iron, titanium, chromium, and aluminum. Of iron lines 136 were reversed, 

 29 titanium lines, 16 chromium lines, and 2 of aluminum. Most if, not 

 all of the strong lines of the three metals first named may be reversed 

 by proper management of the atmosphere and supply of metal in the 

 crucible Fragments of magnesium dropped into the crucible aid the 

 reversal. In this way the reversal of the strong iron Unes about the 

 solar lines L and M, four- strong lines below IST, the line O, all the strong 

 lines from S? to [J, inclusive, and two strong groups still more refrangi- 

 ble, was accomplished. {Nature, June, 1881, xxiv, 206.) 



Huggins has photographed the spectrum of the hydrogen flame burn- 

 ing in air. Though so feeble, yet its spectrum shows a group of lines 

 in the ultra-violet, limited on the more refrangible side by a pair of 

 stong lines of wave-length 3062 and 3008, and on the less refrangible 

 two less strong lines of wave length 3080 and 3090. Beyond this the 

 spectrum continues by nearly equidistant pairs of lines, among which 

 are two of w^ave-length 3167 and 3171, up to wave-length 3290. This 

 entire group the author regards as due to the vapor of water. It is 

 equally observed when the flame is surrounded with oxygen or air. {Ann. 

 Chim. Phys., July, 1881, V, xxiii, 372 ; Proc. Hoy. Sue, 1880, xxx, 576 ; J. 

 Fhys., February, 1881, x, 84.) 



Liveing and Dewar have confirmed the above supposition of Huggins. 

 The spectrum is not only obtained when hydrogen and hydrocarbons 

 are burned in oxygen, but also when non-hydrogenous gases are burned,^ 

 if they are moist. On drying the gases carefully this spectrum disap- 

 pears. {Proc. Roy. Soc, xxx, 580 j J. Phys., February, 1881, x, 85.) 



