58o 



A^A TURE 



[October 4, 1906 



a vacuum, and subsequently in. the gas considered, for a 

 long time. New wires exhibit peculiar properties, especially 

 in regard to their behaviour under different electromotive 

 forces. Old wires also exhibit hysteretic effects with 

 change of pressure. 



The view is developed that the positive ionisation is 

 caused by the gas adsorbed by the metal and the con- 

 sequence examined of supposing the ionisation to be pro- 

 portional to the amount of the adsorbed gas present. In 

 the case of oxygen, by making the assumption that the 

 rate of increase of the amount of the adsorbed gas is pro- 

 portional jointly to the concentration of the external dis- 

 sociated oxygen and to the area of " unoccupied " platinum 

 surface, whilst the rate of breaking up is proportional to 

 the amount present, a formula is obtained which agrees 

 with the experimental results. This formula is that the 

 ionisation i = A/>/(B-)-/)), where ^ = {kV+\k-)\-\k, P 

 being the external pressure and k the dissociation constant 

 of oxygen ; A, B, and fe are constants depending on the 

 temperature, and are of the general form a9*-e~i>ii. Thus 

 this view accounts for both the temperature and pressure 

 variation. 



The positive ionisation from the outer surface of a hot 

 platinum tube in air is increased when hydrogen is allowed 

 to diffuse through from inside the apparatus. The in- 

 crease in the ionisation is proportional at constant tempera- 

 ture to the quantity of hydrogen escaping from the surface 

 in unit time. 



The negative ionisation from hot platinum in air is un- 

 altered when hydrogen is allowed to dilTusc out through 

 the platinum. 



These results show that neither the negative nor the 

 positive ionisations usually observed with hot platinum 

 heated in air or oxygen are due to residual traces of 

 absorbed hydrogen. 



A wire which has been heated in hydrogen furnishes a 

 negative ionisation which is very big compared with that 

 from a wire heated in oxygen at the same temperature. If 

 the hydrogen is at a pressure of the order of i mm. the 

 negative ionisation can be rapidly reduced to a much 

 smaller value by applying a high negative potential to the 

 wire. The wire subsequently recovers its ionising power 

 if the potential is reduced again. Under these conditions 

 the ionisation varies in an interesting way with the time. 

 The reduction in the ionising power of the wire appears 

 to be caused by the bombardment of the surface by positive 

 ions produced by collisions. 



When a platinum wire, which has previously been 

 allowed to absorb hydrogen, is heated for a long time in 

 a good vacuum so as to expel the gas, its ionising power 

 does not appear to be reduced. The ionisation apparently 

 is not a definite function of the quantity of gas absorbed 

 by the wire. 



Paris. 



Academy of Sciences, September 24. — M. A. Chauveau 

 in the chair. — The colour and spectra of solar promin- 

 ences : M. Ricco. Direct observation of the eastern group 

 of protuberances during the total eclipse of 1905 showed 

 that the colour was different in different parts, and 

 especially at the edges, the latter showing a play of colours. 

 The bodv of the protuberance was purple-red, the outside 

 was violet-blue, the summit was pure violet, nearly white, 

 and exceedingly brilliant. Two photographs of the spec- 

 trum were taken, enlarged reproductions of which are 

 given. — The application of M. E. Borel's method of sum- 

 mation to generalised trigonometrical series : A. Buhl. — 

 The amplification of sounds : M. Dussaud. The vibra- 

 tions from any source of sound are received on a mem- 

 brane, and this, either directly, or through a solid, acts 

 on a jet of compressed air. The sound is in this way 

 faithfully reproduced by the jet of air, the ainount of 

 amplification depending only on the power of the motor 

 used in the compression. — The recent scientific cruise of the 

 Otaria : Teisserenc de Bort. 



New South Wales. 



Linnean Society, Augu'st i. — Prof. T. P. Anderson Stuart, 

 president, in the chair. — The Australian Melaleucas and 

 their essential oils, part i. : R. T. Baker and H. G. 

 Smith. In this series of papers on the Melaleucas and 

 their essential oils, of which this is the first, it is the 



authors' intention to follow out this research on the same 

 lines as those adopted in the work on Eucalypts and their 

 essential oils. Bulk material was employed in obtain- 

 ing the results given in the paper. The Melaleucas are 

 commonly known as " tea trees," and are distributed 

 throughout the whole continent of Australia, and so are 

 familiar plants in the bush. Two species form the subject 

 of this paper, viz. M. thymifolia, Sm., and M. Unariifolia, 

 Sm. — lid's opaca, F.V.M., and its enlarged rootstock : 

 R. T. Baker and H. G. Smith. The occurrence of these 

 enlarged rootstocks, weighing from 20 lb. to 25 lb., in the 

 Australian species of Vitis, has been recorded by Baron 

 Mueller, Thozet, Roth, and others, but no chemical in- 

 vestigation of their composition appears to have been made. 

 Such an investigation forms the basis of tliis paper. From 

 the results a close affinity between the carbohydrates of 

 this " tuber " and those belonging to the true gums is 

 shown, and the alteration products are more in the direc- 

 tion of the sugars than the starches. — Investigation of the 

 disease in cattle known as " rickets," or " wobbles," and 

 examination of the poisonous principle of the Zamia palm 

 (Macrozamia Fraseri) : E. A. Mann and T. I. Wallas. 

 The authors for some time have been carrying on investi- 

 gations on the above subject, as the result of which they 

 have come to the conclusion that the effects upon cattle 

 induced bv eating the Macrozamia Fraseri are caused by 

 the presence in the plant of acid potassium oxal«te (salts 

 of sorrel). This is a confirmation of the results of an 

 analysis made by a Mr. Norric prior to 1876, and reported 

 to the Royal Society of New South Wales by Dr. F. Mil- 

 ford (Journal of the Society, vol. x., p. 295). 



CONTENTS. PAGE 



The Evolution of the Globe. By A. H .... 557 



The Genesis of the Inventor. By \A;. H. S 559 



Biological Philosophy 560 



Biology of the Frog. By F. W. G 560 



Our Book Shelf: — 



Oltmanns : " Morphologie und Biologie der Algen." 



— George Murray, F.R.S 561 



Beaiiverie and Faucheron : " Atlas colorie de la Flore 



alpine " 5^1 



Letters to the Editor : — 



Measurement of Resemblance. (I/ltnti-afed.) — Dr. 



Francis Gallon, F.R.S 562 



Models of Atoms.— Prof. Alfred W. Porter ... 563 

 Chemical and Electrical Changes induced by Light. — 



H. S. Allen 564 



The Rusting of Iron.— Dr. Gerald T. Moody ... 564 

 Remarkable Rainbow Phenomena.— Prof. J. M. 



Pernter 564 



Fugitive Coloration of Sodalite.— Jas. Currie . . . 564 

 The Quatercentenary Celebrations of the Univer- 

 sity of Aberdeen. (1 11 II si rated.) ....... 565 



Two Books on Angling. (Illustrated.) By J. J. . . 568 

 Prof Ludwig Boltzmann. By Prof. G. H. Bryan, 



F.R.S 569 



Notes 570 



Our Astronomical Column : — 



Comet igoe.' (Kopfl') 575 



Finlay's Comet, 1906;/ 575 



A New Form of Wedge Photometer 575 



Occultation of a Star by Venus 575 



Results of the International Latitude Service, 1902- 



1906 575 



The Amana Meteorite 575 



Botany at the British Association 575 



The Archaeological Congress at Vannes 577 



A New Specimen of the Okapi 57S 



University and Educational Intelligence 578 



Societies and Academies 579 



NO. 1927, VOL. 74] 



