494 



NATURE 



[December 31, 19 14 



beds north of the Carpathians are studied by W. 

 Petrascheck (1912, p, 75), who indicates (p. 92) an 

 interesting groove, parallel with the range, in which 

 they assume an unexpected thickness above the Coal- 

 Measures. The problem of their faulting-down, in- 

 folding, or original def>osition in a hollow of erosion, 

 reminds us on a smaller scale of that of the Indo- 

 Gangetic plain (see Nature, vol. xciv., 1914, p. 347)- 

 W. von Friedberg, of Lemberg (1912, p. 367) compares 

 the fossil contents of the Polish Miocene w^ith those of 

 Miocene beds in Austria, North Italy, and France, 

 and concludes that the Burdigalian is absent, that the 

 salt-series is Helvetian, and that the Tortonian extends 

 below and also above the gypsum-bearing strata of 

 Podolia. The beds with the brackish-water mollusc 

 Oncophora are held to be somewhat younger 

 than those of Bavaria, and to represent (p. 387) the 

 first arrival of the Miocene sea in Podolia in 

 Upper Helvetian times. References to these beds In 

 Moravia will be found in a note by A. Rzehak (1912, 



P- 344)- 



An interesting feature in mountain-structure is 

 shown in sections bv G. Geyer (1913, p. 293) of the 

 Toten Gebirge on the border of Styria and Upper 

 Austria, where gypsum-bearing beds have been 

 squeezed up like dykes into limestones of much later 

 date. As an example of critical reviewing, we may 

 cite the extremely valuable summary by F. Katzer 

 (191 1, p. 387) of Cvijic's researches in Macedonia and 

 the Balkan peninsula as far as the Dardanelles, which 

 have been mostly published in the Servian language. 

 The origin of the Bosporus-Dardanelles river-cut 

 comes in question (p. 417). We have kept until the 

 last a mention of a discussion by O. Ampferer of 

 Penck's well-known association of terminal moraines 

 and outwash-plains (1912, p. 237). While we think 

 that Ampferer distinctly underestimates the amount of 

 water that may escape from an ice-front of continental 

 magnitude through a loosely piled block-moraine, his 

 citation of the filtering effect of a terminal moraine 

 is distinctly useful. He thus cannot admit the asso- 

 ciation of a large terminal moraine with an extensive 

 "apron." The two structures, for him, should be in 

 inverse proportion. Ampferer does good service (p. 238) 

 in pointing out an anomaly in Penck's diagram of a 

 double moraine-wall enclosing a "Zungenbecken." 

 This figure has been extensively reproduced, but has 

 puzzled other geologists. How was the outer moraine 

 piled up if the inner one was not destroyed? On the 

 other hand, if it is the older of the two, why do its 

 outwash-products overlie those of the inner wall? 



G. A. J. C. 



ON SALTS COLOURED BY KATHODE 

 RAYS.^ 



■pERHAPS a part of the phenomena which I am 

 -*- about to discuss is already familiar to you all. 

 I shall not bring forward many hypotheses. So you 

 will perhaps ask why I should speak at all. And, 

 in fact, apart from reference to certain facts not pub- 

 lished hitherto, my intention is mainly to invite the 

 interest of men younger and abler than myself in a 

 class of phenomena which seem to constitute a new 

 condition of matter, but on which very few have yet 

 worked. 



If kathode rays fall on certain salts — for example, 

 common salt, or chloride of potassium, or potassium 

 bromide — vivid colours are produced immediately on 



1 By Prof. E. Goldstein. A paper read before Section A cf the BritUh Asso- 

 ciation at the Australian meeting, and ordered by the General Committee of 

 the Association to be printed in extenso. 



NO. 2357, VOL. 94] 



these salts. ^ Thus common salt becomes yellow-brow n 

 (like amber), potassium chloride turns into a beautiful 

 violet, potassium bromide becomes a deep blue colour 

 quite like copper sulphate. Here you see a specimen 

 of common salt transformed in this way on the sur- 

 face of the single crj^stals into a yellow-brown sub- 

 stance. I show also sodium fluoride, which takes a 

 fine rosy colour. 



The colours so acquired in a very small fraction of. 

 a second may be preserved for a long time, even for 

 many years, if the coloured substances are kept in the 

 dark and at low temperatures. But in the daylight, and 

 also under heat, the colours will gradually disappear 

 until the original white condition is reached again. 



The colours of different salts are sensitive to heating 

 in a very different degree. I could show you the 

 yellow sodium chloride, prepared some months ago in 

 Europe, but I cannot show you here the violet KCl 

 and the blue KBr, because these colours, even in the 

 dark, do not stand the heat of the equator. The same 

 salt, if dissolved, may keep very different colours, 

 according to the medium in which it has been dis- 

 solved, even when the pure medium itself cannot be 

 coloured at all by kathode rays. I am speaking of 

 solid solutions, produced by fusing a small quantity— 

 for instance, of common salt or of certain other alkali 

 salts — together with a great mass of a salt which 

 remains itself colourless in the kathode rays, as, for 

 example, the pure potassium sulphate. Lithium 

 chloride acquires a bright yellow colour in the kathode 

 rays ; but if dissolved in potassium sulphate a lilac 

 hue is produced, as you may see in this specimen. 

 Likewise the pure carbonate of potassium acquires a 

 reddish tint, but after dissolving it in the potassium 

 sulphate it becomes a vivid green in the kathode 

 rays, as you see here. 



Very small admixtures are sufficient to produce 

 intense colours. So 1/25,000 of carbonate will pro- 

 duce the green colour in the potassium sulphate ; 

 even 1/100,000 gives a marked colour, and an amount 

 of certain admixtures, which I estimated as 1/1,000,000 

 only, may produce a slight but quite perceptible 

 coloration in some salts. So if you work with 

 potassium sulphate which you obtain from chemical 

 factories guaranteed as chemically pure, you may 

 observe a set of different colours in these preparations 

 under the kathode rays, by which you will detect the 

 nature of the different small admixtures which adhere 

 to the pretended pure preparations of the different 



j factories. In this way a new analytical proof, much 

 more sensitive than the ordinary chemical methods, is 

 obtained, and impurities may be detected even when 

 a certain specimen of salt contains more than a single 

 impurity, because the colours produced by different 

 admixtures generally disappear with different speed 



I in the daylight or under rise of temperature. For 

 instance, the ordinary potassium sulphate turns to a 

 dark grey with a slight greenish tint at first. After 

 a short while the very sensitive grey will disappear, 

 simply under the ordinary temperature of the labora- 

 tory room, and a vivid green comes out. The grey 

 hue indicates a very small amount of sodium chloride, 

 1/100,000 or so, and the remaining green indicates 

 the admixture of a carbonate. Here are some pre- 

 parations of potassium sulphate each containing a 

 single small admixture (K^CO,, Li^CO^, LiCl, KCl, 

 KBr). You will notice how different are the colours 

 of the originally white substance, varying from green 



I to bluish-grey, ash-grey, greyish-blue, and violet. 

 By fractional crystallisation one may finally get a 

 really pure preparation of potassium sulphate, which 



- E. Goldstein, IViedem. Ann., liv., 371 ; Ix., 491 ; Phys. Zcitschr., iii., 

 149 ; Sitziingsber. Ber. Akad. d. IViss., 1901, 222. 



