238 



NATURE 



[April 21, 1910 



section constant. The metals treated were lead and a lead- 

 tin alloy ; the general nature of the results was the same 

 in both cases. When suitably loaded there is a rapid 

 initial flow which gradually settles down to a steady flow, 

 for which the rate per unit length of wire flowing is 

 constant right up to breaking. Throughout the experi- 

 mental range the extension can be represented closely by 

 the formula 



i8 is taken as a measure of the more rapid initial flow, 

 which we call the j8 flow ; /f as a measure of the coefficient 

 of viscous traction. The curves «/ (stress) against stress 

 are hyperbolae with one asymptote parallel to, one steeply 

 inclined to, the axis of stress. ;8 tends to become constant 

 as stress increases ; for a series of experiments on lead 

 done at i6o° C. ^ tends to the same constant value as 

 for the series done at room temperature. This supports 

 the suggestion that jS measures a definite physical effect, 

 dependent on some geometrical structure. For the alloy 

 the /3 flow is relatively very small. — Clive Cuthbertson 

 and Maude Cuthbertson : The refraction and dispersion 

 of argon, and re-determinations of the dispersion of helium, 

 neon, krypton, and xenon. The refractive index of argon 

 has been determined for seven points in the spectrum with 

 improved apparatus, and careful re-determinations have 

 been made of the dispersion of the other four inert gases 

 in order to bring them all up to the same level of accuracy. 

 The refractivities are expressed in the form 



M-i = C/(.v-n^), 

 and the constants of these equations, calculated from the 

 observations by the method of least squares, are shown 

 in the following table : — 



Klement <" > to-27 «„-2 y ,o-07 



Helium 2-42476 ... 34991-7 



Neon 5-18652 ... 38916-2 



Argon 9.43264 ... 17008-9 



Krypton 10-6893 ... 12767-9 



Xenon 12.2418 ... 8977-9 



The values of the refractivities derived from these equations 

 generally agree with those found experimentally to one or 

 two points in the fifth significant figure. It is satisfactory 

 to find that the values of n^ now obtained by these more 

 accurate measurements do not differ by more than 2 per 

 cent, from those published by the authors last September. 

 — Dr. J. O. Wakelin Barratt : The action of the radiation 

 from radium bromide upon the skin of the ear of the 

 rabbit. The ear of the rabbit was exposed to the action 

 of the radiation from i mg. of radium bromide spread 

 over a circular area of 7 mm. diameter, and the resulting 

 pigmentation of the skin was studied. It was found that 

 pigment was deposited most abundantly opposite the edge 

 of the disc of radium salt. The deposit, when viewed 

 under a low magnification, presented a characteristic 

 reticular appearance. The larger spaces enclosed by the 

 pigment, which were more or less polygonal, contained 

 hair follicle groups, but the smaller spaces were free from 

 hair follicles. A certain amount of pigment was also de- 

 posited in a diffuse manner, chiefly opposite, or a little 

 outside, the edge of the disc. This, when marked, caused 

 the reticular pattern to be somewhat obscured. The 

 deposit of pigment was not quite uniform, but tended to 

 take on a punctate character. Opposite the centre of the 

 disc of radium salt a varying degree of depigmentation 

 occurred, though at the same time here and there a small 

 amount of pigment, arranged in an imperfect reticular 

 pattern, could sometimes be recognised. The pigmentation 

 was chiefly in the epidermis, the cutis vera being less 

 affected. The depigmentation also affected both epidermis 

 and cutis vera, but was, however, more striking in the 

 latter than in the former. No change in the pigmentation 

 of the hair shafts was observed. In a white rabbit the 

 pupils of which presented a red reflex, prolonged exposure 

 to the action of radium bromide caused the appearance of 

 an exceedingly slight reticular deposit opposite the 

 applicator. With this exception, all the rabbits employed 

 had black or mixed black and white coats. Atternpts were 

 made to obtain pigmentation by the action of radium upon 

 human skin, but were not successful. — Prof. Silvanus P. 

 Thompson : A physiological effect of an alternating 

 magnetic field. If in a darkened room, or with eves 

 NO. 21 12, VOL. 83] 



closed, the head is placed in an alternating magnetic field 

 of sufficient intensity, there is perceived over the whole 

 region of vision a faint flickering illumination, colourless 

 or of a slightlv blue tint. The period of the flicker is 

 not well defined. It does not seem to be the same over 

 the whole field of vision at the same time, nor is it equally 

 bright over the whole field of vision. Even in daylight, 

 virith the eyes open, one is conscious of a sensation of 

 flicker superposed on the ordinary vision. It has not yet 

 been definitely ascertained whether there is any relation 

 between the direction of the axis of the field with respect 

 to the position of the skull. No after-effects of any kind 

 have been observed. The alternating magnetic field, the 

 intensity of which (quadratic mean) was about 1000 C.G.S. 

 units, was produced by sending a current of about 180 

 amperes through a coil of thirty-two turns formed into 

 cylindrical form about 9 inches in internal diameter, the 

 current having a frequency of fifty periods per second. 

 No effect on the senses of smell, taste, or hearing has 

 been observed. (Added April 14, 19 10.— Several of the 

 observers have noticed a sensation of taste after two or 

 three minutes in the alternating magnetic field.) 



Faraday Society. April 5.— Dr. T. C. Cain in the chair.— 

 W. P. Dr-eaper : Nature of the action of dyeing. The 

 abnormal reactions obtaining in the case of " ingrain " 

 colours when the dye was produced in situ, as compared 

 with the same dyeing effect when the same dyes are applied 

 as direct dyes in relation to their subsequent resistance 

 to resolution into solvents ; the variations in the rate of 

 fading of picric acid on different fibres under the influence 

 of dehydrating reagents acting through a vacuum as com- 

 pared with the equivalent action on the acid itself ; the 

 abnormal reactions obtained when the dyes of the indicator 

 class [e.g. methyl orange) are subjected to the action of 

 acids in the presence of fibre substances ; the variations in 

 resolution of the dyes from the fibres brought about by 

 differences in temperature of dyeing; all these were, it 

 was claimed, proof as to the important influence of certain 

 factors in determining the fixing power of the fibres for 

 dyes, this varying as the conditions of dyeing. It was also 

 pointed out that the dyes were definitely fixed in some 

 way on animal fibres, so that they might even resist the 

 subsequent action of acids, as proved by these colour 

 changes.— Prof. W. W. Haldane Gee and W. Harrison : 

 The electrical theory of dyeing. The literature relating 

 to the causes of dyeing reveals great differences of opi';»o" 

 as to the physical and chemical phenomena involved. The 

 basis of the electrical theory is that when any two bodies 

 are placed in contact they are oppositely electrified. In 

 the case of tinctorial chemistry, one of the bodies is a non- 

 conducting solid and the other a liquid. There does not 

 seem to be any direct method of obtaining the value of the 

 potential difference between such bodies. The authors avail 

 themselves of the classic theory of von Helmholtz, which 

 enables the potential difference between a liquid and a 

 porous diaphragm to be deduced. They have determined 

 the nature of the charge on the particles in suspension 

 and in colloidal solution, and find that in water all basic 

 substances are positive, the hydrochlorides of basic dyes 

 positive, all acid substances negative, and most neutral 

 substances negative. They find the speed of the particles 

 under electrical stress to be of the order 20x10- cm. 

 per second, per volt, per cm. Negatively charged particles 

 attain their maximum speed at about 40° C. By measur- 

 ing the dffference of electrical pressure between the two 

 sides of a diaphragm when the liquid is filtered under 

 mechanical pressure, the authors find the approximate 

 value of the contact difference between fibres and water 

 to be :— cotton, o-o6 volt ; silk, 0-22 volt ; wool, 0-90 volt. 

 The influence of temperature shows a maximum charge 

 at about 40° C, and a minimum at about 80° C. 



Linnean Society, April 7.— Dr. D. H. Scott. F.R.S., 

 president, in the chair, succeeded by Mr. H. W. Monckton, 

 treasurer and vice-president.— A. Henry: Elm seedhngs 

 showing Mendelian results. There are but two species ot 

 elm in Britain, Ulmus montana. With., and U. glabra. 

 Mill. : both are known in the east of England as Wych- 

 elm." There are, in addition, manv so-called varieties, 

 the most remarkable being the " English elm "of British 

 botanists and foresters, confined to the south of England, 



