574 



NA TURF 



[April 16, 1903 



probably possess rational indices, and must, therefore, be 

 inclined at certain definite angles to the octahedron face ; 

 but the indices are very high numbers. 



In other experiments crystals of alum were measured 

 after growing for several hours in solution kept continually 

 agitated in order to eliminate the action of the concentration 

 streams. Almost no effect was produced upon the angles 

 of the vicinal faces, which are, therefore, not due to these 

 streams. 



Every point within a crystal has at some time been a point 

 on the surface, and has been subject to the conditions of 

 equilibrium between crystal and solution which prevail there. 

 It is believed by the author that a study of the vicinal planes 

 and of the liquid in contact with them may lead to some 

 understanding of these conditions. 



In order to ascertain the composition of this liquid, its 

 refractive index was determined by means of the same 

 goniometer by the method of total internal reflection within 

 the growing crystal, for alum, sodium chlorate, and sodium 

 nitrate. 



In each case the liquid in contact with the growing 

 crystal was found to be slightly supersaturated. It was 

 not found to exhibit double refraction even in the case of 

 sodium nitrate. 



The author suggests that vicinal faces grow upon a crystal 

 in preference to simple forms, because the crystallising 

 material descends upon the growing face in a shower which 

 is not very dense. 



" On a New Series of Lines in the Spectrum of Mag- 

 nesium." By A. Fowler, A.R.C.Sc, F.R.A.S., Assistant 

 Professor of Physics, Royal College of Science, South 

 Kensington. Communicated by H. L. Callendar, F.R.S. 



The paper records the appearance of faint lines at approxi- 

 mate wave-lengths 4511-4, 42510, 41068, and 40183 in 

 the arc spectrum of magnesium when metallic poles are 

 used. A mere inspection of the photographs suggests that 

 these lines constitute a regular series, associated with the 

 much stronger series described by Rvdberg having wave- 

 lengths 552875, 4703-33, 435218, 4167 81, 4058-45, and 

 3987-08, and this view seems to be confirmed by calculation. 



A formula which has been found to give good results 

 for series in general, nann-h 



C 



11-llx, --. ; rs ' 



( m -f- fx)~ - m n 

 gives for the two series the equations : 



" Rydberg " seiies, « = 26, 601 '49 - 

 New series, 11 = 26, 587^4 



107,071 37 



{lit + I - 2304)-+2'I3282 



100,033 6 



{m + 0495)- + 2 -3S9" 9 

 n being the oscillation frequency in vacuo in each case. 



The convergence frequency of the new series is as nearly 

 equal to that of the Rydberg series as can be expected with 

 the comparatively rough wave-lengths employed, and in 

 each case the constant t« is of unusual magnitude. 



It is concluded that the arc spectrum of magnesium in- 

 cludes two subordinate series of single lines in addition to 

 the two well-known subordinate series of triplets. No such 

 combination of series appears to have been previously noted 

 in the spectrum of a metal. 



" On the Dependence of the Refractive Index of Gases on 

 Temperature." By George W. Walker. Communicated 

 by Prof. J. J. Thomson, F.R.S. 



Mascart found that the temperature coefficient of refrac- 

 tive index of gases always exceeded the theoretical co- 

 efficient given by Gladstone and Dale's law. In the case 

 of air his results do not agree with those of Lorenz and 

 Benoit, who found a coefficient which agrees with the 

 theoretical law. The present paper gives an account of 

 the author s experiments on air, H„, CO„, SO, and NH 3 . 



Jamin's interference method was" used^ and'the accuracy 

 obtained in the value of M _, was about one part in 600. 

 the temperature coefficients obtained were substantially less 

 than Mascart s values, but they still differ from the 'rW- 

 retical law. 



"The Electrical Conductivity imparted to a Vacuum by 

 Hot Conductors." By O. W. Richardson, B \ B Sc 



< ommumcated by Prof. J. J. Thomson, F.R.S. " 



NO. 1746. VOL. 67] 



This paper is an investigation of the conditions which 

 determine the rate of escape of negative electricity from hot 

 metals at low pressures. 



The results of the experiments are explained on the cor- 

 puscular theory of conduction in metals. Assuming that 

 the corpuscles which strike the surface are kept in the 

 metal at ordinary temperatures by a surface discontinuity 

 of potential, they will escape when their kinetic energy 

 exceeds a certain value. Calculating in this way, the 

 number of corpuscles which escape per second, at tempera- 

 ture 6, is found to be 



XT / Re V - 1R » 



N = 11 ( I e 



\ 211117/ 



where n = the number of free corpuscles per c.c. of the metal, 

 R = the gas constant for one corpuscle the mass of which is 

 m, and *=the work done by a corpuscle in passing through 

 the surface layer. 



The saturation current is equal to N multiplied by the 

 charge on an ion. 



The saturation current, in the case of platinum and carbon, 

 and the current under a constant voltage, in the case of 

 sodium, where the current could not be saturated, have been 

 shown to vary with temperature according to a formula of 

 type A6*(! - '' " (A and b being constants), over a large range of 

 values. The range of current examined is : — 



For platinum from IO~ 10 to 10 -3 amperes per sq. cm. 



For carbon from IO -a to 2 amperes per sq. cm. 



For sodium from 10~ n to 2 x io~ 2 amperes total current. 



The corresponding ranges of temperature for carbon and 

 sodium are roughly from 1000 C. to 1600 C. , and from 

 ioo° C. to 450 C. respectively. 



From the values of A, the number of free corpuscles per 

 c.c. in each conductor is calculated. In the case of 

 platinum the number agrees with that found by Prof. 

 Patterson by another method, but the values for the other 

 conductors are absurdly large. Reasons for the discre- 

 pancy are assigned. 



The values of the discontinuity in the potential at the 

 surface of the metal are obtained from those of b. They 

 are found to be: for sodium, 245 volts; for platinum, 4'i 

 volts; and for carbon, 6'i volts. The values obtained lead 

 to the conclusion that the work required to force a corpuscle 

 out of a metal varies, approximately at any rate, inversely 

 as the cube root of the atomic volume. 



The enormous currents obtained at such very low pressures 

 (as much as two amperes per sq. cm. at 1/600 mm. in the 

 c ase of carbon) show that the leak is not produced by the 

 interaction of gas and metal. The results also furnish a 

 complete explanation of the Edison effect. 



" On the Evolution of the Proboscidea." By Dr. C. W. 

 Andrews, 



Chemical Society, April 2.— Prof. W. A. Tilden, F.R.S., 

 president, in the chair. — The following papers were read :— 

 The dioximes of camphorquinone and other derivatives of 

 isonitrosocamphor, by Dr. M. O. Forster. The four 

 possible dioximes have been prepared in a pure state, and 

 their principal properties ascertained ; from these a number 

 of interesting derivatives have been obtained. — Reversibility 

 of enzyme or ferment action, by Mr. A. C. Hill. In con- 

 tinuation of the author's researches on this subject attempts 

 have been made to isolate the reversible products produced 

 by the action of enzymes on monosaccharides. The new 

 biose revertose has been obtained in this way by the action 

 of yeast ferment upon glucose, and has been characterised 

 by the preparation of its well-crystallised phenylosazone. — 

 Discoloured rain, by Mr. E. G. Clayton. The author has 

 examined the terra-cotta coloured deposit obtained from the 

 rain which fell generally in the south of England on 

 Sunday, February 22, and finds that this deposit was merely 

 wind-borne dust from the roads and lanes of Wessex. Dr. 

 Mill, in the discussion which followed, stated that fifty 

 specimens collected in various parts of Europe were now- 

 being examined by the officials of the Geological Survey, 

 and that a preliminary examination of some of these samples 

 led him to believe that the explanation of the presence of 

 this solid matter in the rain was less simple than Mr. Clay- 

 ton had suggested.— The absorption spectra of nitric acid 

 in various states of concentration, by Prof. W. N. Hartley. 

 Photographs of the spectra of nitric acid solutions indicate 



