2o6 



KNOWLEDGE & SCIENTIFIC NEWS. 



[August, 1905. 



the crj'stals is unattended by any emission of light whatever, 

 but that if the flask be shaken the crystals are ruptured by 

 contact with the glass or each other and then produce the 

 flash. The property is by no means a fugitive one. and 

 the dry cr>-stals will yield sparks months afterwards if 

 rubbed with a glass rod. Mpreover, contrary to the 

 statements of the text books, the emission of' light is 

 produced as readily by cr>-stals formed from the opaque 

 variety of oxide as by those from the vitreous modiflcation. 

 The phenomenon is thus another instance of triboluinincsccnce, 

 the name given to the property possessed by many crvstal- 

 line substances of emitting light when struck or rubbed. 

 Herr Tchugaeff has shown that very many bodies possess the 

 same power. Thus, of 400 substances examined by him, 121 

 were found to emit light, the alkaloids, as a class, being par- 

 ticularly active, but only 6 out of no inorganic bodies showed 

 the phenomenon. The colour of the light varied with the 

 diff^erent substances, and its intensity could be classified 

 according to an arbitrary scale in which uranium nitrate was 

 taken as typical of the first class, tartaric acid of the second, 

 and ammonium oxalate of the third. The nature of the light 

 emitted by arsenious oxide has also been studied by M. 

 Guinchant, who finds that it has a continuous spectrum in the 

 visible part of which the green and yellow rays predominate, 

 though red rays are also present. The light does not affect 

 an electroscope, but has a strong action upon a photographic 

 plate, and is apparently identical in character with the light 

 emitted by solid bodies in a state of incandescence. 



The Physiological Action of Air in 

 Crowded Roonns. 



It is a commonly accepted belief that the unpleasant effects 

 produced on the human system by the air in overcrowded 

 rooms is due to volatile products given off bv the skin and 

 lungs; but experiments made by Dr. Paul of the Hrcslau 

 Hygienic Instituteappearto indicate that the main cause is the 

 retention of heat by the body. Lnder normal conditions heat 

 is lost by conduction, radiation, and evaporation of moisture, 

 as well as during respiration. The loss of heat by conduc- 

 tion is to a large extent prevented in crowded rooms, in 

 which the air is usually of a relatively high temperature, 

 and contains a high proportion of moisture, while the loss by 

 radiation is very incomplete when the body is surrounded by 

 others at about the same temperature. In Dr. Paul's experi- 

 ments it was found that headache and all the other unpleasant 

 symptoms could be entirely prevented by regulation of the 

 heat, even when the air was saturated with respiration pro- 

 ducts, and contained as much as 15 per cent, of carbon 

 dioxide ; whereas without this regulation of temperature they 

 appeared even when absolutely pure air was breathed. The 

 retention of heat could be demonstrated objectively by the 

 rise in temperature of the skin. 



The Action of Hydrogen Peroxide on a 

 Photogra.phic Pla.te in the Dark. 



Systematic experiments have been madu hv Dr. C. t >tsuki, 

 of Tokio, to determine the nature of the changes produced by 

 hydrogen peroxide acting upon a photographic plate in the 

 dark, and to test the assertion that the action of the reagent 

 could penetrate through a sheet of metal (see " K.sowi.edgi; & 

 SciENTiiic NEws,"this Vol., p. 100). It was found that gelatin, 

 celluloid, certain gums, and Canada balsam were permeable, 

 but that paraffin, fish membrane, ebonite, glass, and metals 

 were not. In the experiments with metals the greatest care 

 was taken to insure the absence of minute holes, the thin 

 films being examined under the microscope before and after 

 the exposure. The metals used were zinc, copper, tin, an 

 alloy of gold, silver, and platinum, brass, and aluminium in 

 thin films ranging in thickness from about one thousandth to 

 one tenth of a thousandth of an inch. Out of 47 experiments 

 action upon the plate was only observed three times, and in 

 each case minute holes were found to have been formed by 

 the corrosive action of the hydrogen peroxide vapour upon 

 the metal. The temperature h.id a considerable influence 

 upon the reaction between the gelatin silver bromide and the 

 hydrogen peroxide, lighter or darker zones in the image 

 (GraeU's "border effect") being produced by small varia- 



tions in different parts of the plate or between the plate and 

 surrounding bodies. In some cases the borders were lighter 

 than the centre, while in others the reverse was the case. It 

 is not improbable that this may also account for the curious 

 border produced by the action of wood upon a photographic 

 plate in the present writer's experiment (" Knowlkdge&Sciun- 

 TiKic News," thisVol.,p. 120), assuming th.it hydrogen peroxide 

 was the active agent in this case. Professor Otsuki concludes 

 that the action of hydrogen peroxide upon the silver bromide 

 in to convert it into a lower bromide which can be reduced 

 leadily by the developing solution. It cannot be regarded 

 as due to radiation. 



GEOLOGICAL. 



By EiiwAKD A. Marti.n, F.G.S. 



Erosion in Freshwater Bay. 



The possibility of the sea breaking throui^h what remain of 

 the low-lying cliffs in Freshwater Bay and forming a junction 

 with the waters of the slug,i;ish Vare gives rise to many 

 interesting geological considerations. It is not a little re- 

 markable that a river should take its rise in such close 

 proximity to the sea as does the ^'are, and for an explanation 

 we must look back to a geological time when the sea was much 

 farther away to the south than it now is. Even within the 

 historical period great changes have taken place in connection 

 with the coast of the Isle of Wight, and the extent of the 

 island has dwindled to its present dimensions. When, too, 

 we look at the width of the valley of the ^are, one is apt to 

 wonder how such a slow-flowing stream could ever have had 

 the necessary force to carve a wide valley. The river is now, 

 however, in its old age. Probably it would long since have 

 been silted up, had there been a sufticient watershed to have 

 ensured a plentiful supply of sedimentary material. Now, 

 there is a chance of a new lease of life being given to it, if 

 the dreaded possibility happens, and the sea leaps the barrier 

 at Freshwater Bay, to join hands with the river itself. But 

 there is another possibility of a different nature. Would it be 

 worth while draining tifc upper reaches of the ^'are ? It 

 would not be a difficult matter to prevent tidal action from 

 having any influence beyond the town of ^'armouth ; then 

 much of what is almost stagnant water might be drained, and 

 valuable land in Freshwater Bay saved from destruction. 



The Tatrns of Ticino. 



In pursuance of Prof. E. J. G.irwood's studies into the 

 action of ice, an interesting paper has been read by him 

 before the Geological Society, in which he deals with the 

 formation of the Tarns of the Canton Ticino. Excavation by 

 ice-action, so far as these lakes are concerned, finds no support 

 in the paper in <iuestion. In some cases the ice must have 

 invaded the district from the outside, and from several direct- 

 ions at once. The lakes appear for the most part to be due 

 to structural peculiarities of the district, lying often in lines of 

 junction, or indicating lines of weakness; while at the same 

 time the presence of numerous springs gives rise to a belief 

 that solution may have formed a not unimportant part in their 

 formation. 



GlaciaLl (?) Geology. 



Sir Henry Howorth is excellent company, whether in person 

 or in his writings, and those who have enjoyed his humour as 

 a raconteur will almost feel that he is playing an enormous joke 

 at the expense of the geological world in launching his thou- 

 sand-page work on " Ice and Water." Sir Henry is following 

 up with his usual courage his contentions in regard to the 

 generally-accepted theories of ice-action and water-action, and 

 those who have read and enjoyed "The Glacial Nightmare" 

 and "The Mammoth and the Flood" will be prepared for this 

 further exposition of his views. Almost as one crying alone in 

 the wildern<'ss, his works an- full of ixcellcnl reading, and 

 crowded with data, brought together with infinite patience, 

 and if one is apt to develop too much into an extremist in any 

 particular school of geology, one finds an agreeable corrective 

 here. 



