Prisms of the metals, with a refracting angle of 15*311, were deposited on glass by means of the cathode rays; and the refractive indices determined for red, yellow, and blue light by the methods of deviation, interference, Newton's rings, and immersion in liquids of known refractive index. The results obtained by the different methods show some variation, but they are of the same order. The following are selected as examples (for sodium-light) : copper, 0*46-0.57 ; iron, 1-85 ; lead, 1-95 ;

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... tinum, 1-75-1.88 ; silver, 0.28-0.34; zinc, 2-11 ; magnesium, 0.40 ; gold, 0*58-0*65 ; bismuth, 1-98; nickel, 1.88; brass, 0.66. Further Remarks o n a Formula for the Index of Refraction of Binary Mixtures. ARRIGO MAZZUCCHELLI (Atti 8. Accad. Lincei, 1912, [v], 21, ii, 701--707).-The author sustains and develops his former criticism (A., 1911, ii, 781) in view of the reply of Schwers (A., 1912, ii, 1). L. J. S. R. V. S. Optical Constants of Certain Metals in t h e Ultra-Red. K. FORSTERLING and VSEVOLOD FR~EDEHICKSZ (Ann. Physik, 1913, [iv], 40, 201--232).-The optical constants of silver, copper, gold, platinum, and iridium have been calculated from observations on the influence of the metals on the polarisation of the light reflected from the polished metal surfaces. These observations were made with monochromatic light of wave-length varying from A = 1000 pp to 5000 yp,. According to the electro-magnetic theory, if the dielectric constant may be neglected in comparison with the conductivity, it is to be expected that the relations K = 1 and n = &T will hold good, where K is the index of absorption, n the refractive index, CT the conductivity, and T the period of vibration of the incident light. It has already been shown that these relations are not satisfied in the case of ultra-violet and visible rays, and the data now obtained lead to the same result for ultra-red radiation. The Spectra of Nebula and the Aualogies to be Drawn From Them. JEAN MEUNIER (Compt. rend., 1913, 156, 391-393 . Compare A., 1912, ii, 432; this vol., ii, 24).-The greater part of the nebulz present continuous spectra, but there are some which show a number of definite lines. The author considers that these lines all coincide with definite lines in the solar spectrum, attributeti t o various elements, namely, hydrogen, iron, and titanium, there being thus a marked analogy between the solar spectrum and that of the nebulz. Finally, from Watts' examination of the spectrum from the flame of a Bessemer converter, he draws the conclusion that iron and titanium can exist in flames which are absolutely Absorption Spectra of Some Uraoyl Salts. ARR~GO~MAZZUC-CHELLI atid OLGA GRECO D'ALCEO (iitti tz. Accad. Lincei, 1912, [v], 21, ii, 850-854; 1913, [v], 22, i, 41-43).-1n a recent paper (this vol., i, 160) the authors have shown that a number of uranyl and uranous salts do not form complexes with certain nitrogenous compounds. The present papers record the results of photographic measurement of the absorption bands of solutions of these salts both before and after the addition of the nitrogenous substances, and the results confirm those obtained in the former paper by purely chemical methods. As a control, similar measurements were made with sodium uranyl tartrate and pyridine; the reaction (of whatever nature) which occurs between these substances is indicated by the absorption spectra. Uranous chloride shows the same absorption spectrum alone and after addition of carbamide, so that no additive compound is formed. The spectrum of ~~/ 2 0 -u r a n o u s sulphate is figured, and also the spectrum of the same solution after addition of glycine in the proportion of 24 mols. to 1 mol. of uranium salt; the only difference observable is a slight displacement of the maxima of the bands. The spectra of the two corresponding solutions of uranous chloride (which are also reproduced) do exhibit differences, and in this case the existence of an additive compound has been shown t o be probable by chemical means.