424 



NA TURE 



[September i, 1904 



recorded in their j.ournal, the Indian Forester, and the 

 behaviour of the clumps is being carefully watched, 

 especially as the dying off of the clumps of a species over 

 large areas may mean a serious dearth for several years 

 of the most useful material for the construction of native 

 houses and of many articles of common domestic use. I 

 would therefore invite the attention of those interested in 

 the subject to the pages of the journal mentioned, and I 

 hope Mr. Tingle and others will collect similar information 

 in China. As regards the flowering of cultivated species 

 in the gardens of this country, some very useful information 

 was given by Mr. Bean, of Kew, in the Gardeners' 

 Chronicle for 1903. I am not quite sure that all the flowered 

 clumps of Arundinaria Falconeri will die. I have one in 

 my own garden, and I think it is quite likely to live. I 

 recently saw, in a neighbour's garden, a large clump of 

 A. Simoni which had flowered and apparently died, but the 

 root-stock is now studded with young green shoots, and they 

 look as if they intended to grow. I think it is because all 

 the culms h.ad been cut away after the flowering. 



J. S. Gamble. 

 Highfield, Liss, Hants, .August 14. 



The Spontaneous Scintillations of Hexagonal Blende. 



,'\ SHORT time ago I pointed out in the Chemical Neivs 

 (1C104, p. 33) that scintillations, similar to those produced 

 bv a radium salt, but feebler, can always be observed in 

 hexagonal blende, in the absence of any radium or radium- 

 emanation. 



I have recently made experiments in order to determine 

 whether the blende itself is radio-active, and whether such 

 inherent radio-activity is the cause of the spontaneous 

 scintillations. 



An electroscope was used with parafBn-wax insulation 

 and a long aluminium leaf. The rate of leak was first 

 determined, and then the effect produced on the rate by 

 placing the blende on the brass plate of the electroscope. 

 Two specimens from a French firm were examined in this 

 way, and showed no effect whatever ; they were spread over 

 the plate in the form of powder. 



A specimen from an English firm, in the form of a screen 

 4 cm. square, showed a marked effect, but a piece of writing- 

 paper of the same size produced the same effect : conse- 

 quently, no radio-activity can be attributed to the blende on 

 the screen. .All these specimens showed the scintillations 

 distinctly, and I can only adhere to my original opinion 

 that the scintillations are caused by a spontaneous change 

 in the structure of the crystals. E. P. Perman. 



University College, Cardiff. 



Sooty Rain. 



( SHOULD be glad if any of your readers could explain the 

 following phenomenon : — 



It occasionally happens that on still days, usually with 

 light northerly winds, a heavy shower of rain will carry 

 down a black greasy deposit which forms a film or scum 

 on this and other lakes in the district. It is a recognised 

 nuisance to owners of pleasure boats, as, from the adhesive 

 nature of the scum, scrubbing with soap and water is 

 necessary to remove it. 



This black deposit has been examined for me by a com- 

 petent biologist, and contains no products of organic life. 

 It has, in fact, the appearance and oily character of ordinary 

 soot. I have seen a small handful (when dry) scraped up 

 here from the shore. Sooty rain is the exception, and not 

 the rule. In May last there were about eight days of sooty 

 rain, with the wind out of the north-east. During the last 

 three months, though the lake has risen more than a foot, 

 there has been only one sooty rainfall, viz. on August 17, 

 when the wind was again in the north. 



Yesterday (Sunday, August 21, 4 p.m.) I had an oppor- 

 tunity of observing the formation of the scum, and was 

 surprised to see how quickly it appeared. The day had 

 been still, with heavy clouds at a considerable height coming 

 up slowly from west-south-west, with an occasional light 

 breeze from the north. At 4 o'clock the wind dropped 

 entirely, and a sudden heavy shower of rain fell which lasted 

 about fifteen minutes. 



NO. 1818, VOL. 70] 



As soon as the rain began, the surface of the lake appeared 

 broken up into faintly defined dull and bright patches, which 

 in two or three minutes became strongly intensified without 

 losing their original shape. The dull patches consisted of 

 the sooty film, which was easily observable by dipping in 

 a sheet of white paper, to which the soot adhered. 



The position of the Lake District in regard to manu- 

 facturing centres renders the occurrence of sooty rain under 

 the conditions described rather remarkable. It would be 

 interesting, too, to know why the sooty film should not 

 cover the surface of the water uniformly, instead of in 

 patches. These patches, by the way, are known locally as 

 " tarns, " and are supposed to forecast a spell of bad weather. 



Coniston, Lanes., August 22. J. B. Cohen. 



Adaptive Colours of Eyes. 



Some time ago Prof. Wallace, of the School of Mines, 

 Kimberley, suggested to me the possible e.xplanation of the 

 difference in colour of the light reflected from the iris of 

 the eyes of different people — that it was in accordance with 

 the natural law of protection against external influences. 

 He pointed out that people hailing from regions where blue 

 light is predominant — Swedes, Norwegians, and sailors, for 

 instance — have blue eyes, whilst near the equator, or in 

 sandy climes such as South .Africa, where intense yellow 

 light, is experienced, the eyes take a rich dark yellow hue, as 

 those of tihe Kaffirs and Malays, Italians and Spaniards. 

 The Scotch have blue, the English grey, and the French dark 

 eyes, generally speaking. 



I wish to know whether this novel explanation will bear 

 criticism under the searching light some of your readers 

 may be able to throw on the matter. 



A. Vincent Napier. 



Beaconsfield, Kimberley, South Africa, July 21. 



An Optical Phenomenon. 



Some sixteen years ago I observed phenomena which 

 appear to be related to those mentioned by Mr. Hillig on 

 p. 3b6 of Nature, and by Mr. Walker on p. 3911. A disc, 

 in which was a ring of holes, was rotated between the eye 

 and the sky. I saw coloured patches and rings, changing 

 with the velocity of rotation. The appearances vanished 

 as the rate of rotation increased. The colours were pale 

 green and purple. The purple flowed about as if fluid, and 

 the green appeared as islands mottling its surface. It 

 occurred to rile that there might be some connection with 

 the visual purple of the retina. 



It would be of interest to repeat the experiments, using 

 the different spectral colours, and varying the rates of 

 rotation. 



Intermittent stimulation of the retina may give rise to 

 very curious and interesting results. 



In the concluding chapter of Mr. Bidwell's " Curiosities 

 of Light and Sight " will be found an account of some 

 remarkable effects produced by intermittent illumination. 



Leeds, August 27. C. T. Whitmell. 



The Constitution of Matter. 



Having followed the alniost brilliant discussions concern- 

 ing the constitution of matter which took place at the 

 recent Cambridge British .Association meetings, I was not 

 a little surprised to come across the following remarks made 

 by Ralph Waldo Emerson in 1867. He said : " The chemists 

 already find the infinite variety of things contained in sixty- 

 six elements ; and physicists promise that this number shall 

 be reduced to twenty, ten, five. Faraday declares his belief 

 that all things will, in the end, be reduced to one element 

 with two polarities." 



It would be interesting to know exactly the phraseology 

 in which Faraday expressed this belief. 



R. vV. Emerson merely uses the statement to aid religious 

 views. And yet in several of his writings he has selected 

 almost prophetic utterances concerning science. 



C. Alfred Smith. 



King's College, London, .August 29. 



