METEOROLOGY. 373 



land lies, at least for this year, south of the position of the maximum 

 zone. [Nature, xxix, pp. 226, 343, 409, and 537.) 



366. On page 80, vol. xxx, of Nature, Tromholt states that a few- 

 lovely days have enabled him to set up his artificial-aurora apparatus 

 on the summit of Esja, but without as yet any optical results. 



367. In the autumn of 1884, Prof. Tromholt returned to Bergen where 

 he will work on the great catalogue of auroras observed in ISTorthern 

 Euro])p, which with other works is being prosecuted at the expense of 

 the Norwegian government. {Nature, xxx, p. 592.) 



XL — (a) Eefraction and mikage : (/>) Scintillation ; (c) Spec- 

 troscopy AND PhOTOSPECTROSCOPY ; PHOSPHORESCENCE, ETC. 



{d) Halos; Eainbows; (e) Photometry; Colorometry; Twi- 

 light, ETC. 



368. T. von Oppolzer, of Vienna, at a meeting of welcome in honor 

 of the session of the International Polar Commission April 21, 1884, de- 

 livered an address ui)on the connection between atmospheric refraction 

 and the distribution of temperature thronghout the air. After explain- 

 ing his formula for refraction, based on the assnmption that the change 

 of temperature with altitude is proportioned to the change of density of 

 the air, and having shown that this empirical assumption agrees with 

 the observations at least for the lowest 10 kilometers, he says that it 

 may now be aslced whether the observed atmospheric refraction jnay 

 not give some clue to the actual temperatures at great heights in the 

 air where direct observations can never hope to reach. This, however, 

 he answers in the negative, but, in regard to the lower .strptii, it is en- 

 tirely possible for meteorology to derive assistance from astronomical 

 observations, though the latter will undoubtedly receive much more 

 assistance from the former. This essay is printed as an a]ipendix to 

 the Zeitschrift of the Austrian xissociation for May, 1884. {Z. 0. G. 

 M., XIX, p. 265.) 



369. P. G. Tait gives a thorough elucidation of the atmospheric con- 

 dition necessary to produce forms of mirage. This is in continuation of 

 his former paper on mirage, and as an example of an ai)plication of 

 Hamilton's general method in optics, which is being published by the 

 Koyal Society of Edinburgh. {Nature, xxviii, p. 84.) 



370. C. Montigny has for some time observed the colors of the stars 

 by means of a scintillometer, and among other things has discovered 

 that the bine color ]ire vails remarkably when rain api)roaches, and 

 this phenomenon can therefore be used for the prediction of rain. In 

 June, 1883, having observed that the blue color had been absent for three 

 months, and that the green was becoming more ])rominent, Montigny ven- 

 tured the i)rediction that the (piantity of water in the upper strata of 

 air had become diminished, and that during the year 1883 fewer long 

 rains would occur. This prediction having been well fulfilled, Montigny, 

 in April, 1884, made the same observations and renewed the same pre- 



