I-'ebrtjary 1 6, 1922] 



NA'rVRE 



225 



igard fiKcaia and its objects as of no metaphysical 

 iportance, and an understanding of the nature of 

 khis section is necessary if we are to grasp Plato's 

 Jeneral theory of knowledge. Even Plato's theory 

 lat art must be classified under this first cognitive 

 ictivity of the spirit is in its essence sound, in spite 

 >f the fact that some of the conclusions which he 

 lerived from it were mistaken. 



Association of Economic Biologists, January 27. Sir 



•avid Prain, president, in the chair. — E. P. Stebbing : 

 The importance of scientific research in forestrv and 

 Its ix>sition in the Empire. In India a research insti- 

 tute was formed at Dchra Dun in 1906, and the fully 

 -juipped building completed by 1914, It has now 

 come necessary to decentralise research work to 

 >me extent, and a fine institute is already in exist- 

 ice at Coimbatore, in Madras. Elsewhere in the 

 ipire, with the exception of Canada and at home, 

 ke forest services are only in the initial stages of the 

 production of the wofk. A start should be made in 

 »e branches of forest botany and forest economics. 

 (t home a well-equipped research institute is most 

 rgently needed which would work in collaboration 

 rith the educational centres the staffs of which have 

 |me available to devote to research work. Until 

 ich a research institute is established full use should 

 made of centres the equipment of which is adequate 

 • carrying on research on the lines which the 

 •orestry Commission may suggest. 

 Physical Society, January 27.— Sir William Bragg in 

 te chair,— T. H. Littlewood : The diffusion of solu- 

 >ns. An optical method is described for finding the 

 concentration at various depths in a diffusing solu- 

 tion. The solution is contained in a closed vessel, the 

 top and one side of which are of glass. On the glass 

 side is a vertical scale. This vessel is immersed in 

 water containing a mirror which can be rotated, and 

 the position of which is read on a graduated scale by 

 a telescope which carries a horizontal wire illuminated 

 by sodium light. The mirror is adjusted so that the 

 image of the wire, after twice passing through the 

 liquid, is seen on the cross wires of the telescope, and 

 the reading on the vertical scale is also observed. 

 The concentration can be determined at different 

 depths with an accuracy of about 005 gr. per litre. 

 I'Vom a series of measurements at different times the 

 coefficient of diffusion can be calculated. Sufficient 

 data can be obtained in less than a dav.— H. R. 

 Nettieton : A special apparatus for the measurement 

 at various temperatures of the Thomson effect. The 

 short^ wire under test (S.W.G. 18) passes through 

 electrical heaters which may quickly be brought to, 

 and maintained at, steadv temperatures differing bv 

 some 50° C. over the range 20° C. to 2^0° C. A 

 short coil of the finest double silk-tovered copper wire 

 fS.W.G. 44) acts as the Thomson-Joule heat detector.— 

 J. J. Manley : A defect in the Sprengel pump : its 

 causes and a remedy. A plan wherebv the limitations 

 and irregularities of the Sprengel pump resulting 

 from the presence of air skins upon the interior sur- 

 faces mav be made negligible is described. The effi- 

 ciency of the new pump is superior to that of the 

 older forms, and appears to be constant. 

 Dublin. 

 Royal Dublin Society, Januarv 24,— Mr. G. Fletcher 

 in the chair.— H. H. Poole : Some notes on the dis- 

 tribution of activity in radium thctapy under different 

 conditions of screening. Tests were made of the 

 screening erfect of various materials on the complex 

 .radiation emitted from a thin-walled emanation tube. 

 From these the activitv at various depths in the 

 tissues were calculated for several arrangements of 

 surface applications and for emanation needles. 

 XO. 2729, VOL. 109] 



Edinburgh. 

 Royal Society, January 9.— hror. F. O. Bower, presi- 

 dent, in the chair. — K. iK. houstoun : A new method 

 of investigating colour-blindness, with a description ot 

 twenty-three cases. Ihe meinod was based on Max- 

 well's colour diagram, and consisted in testing the 

 power of discrimmating between contiguous tints of 

 colour as the tint was varied continuously by stages 

 from, say, red to green by an increasing admixture 

 of green with red. The results for each observer 

 were represented by contour lines on the triangular 

 colour diagram. The ability of the observer to dis- 

 criminate between any pair of colours could be seen 

 from his diagram at a glance, irrespective of the 

 terminology of any particular theory. More than 

 1400 students of Glasgow University had been tested 

 during the last four years. All the cases of colour- 

 blindness investigated seemed to be trichromatic in 

 Maxwell's sense, not dichromatic as stated in text- 

 books. Also, two observers v. ho confused ordinary 

 greens and reds were found, on the whole, to have 

 quite as good a power of discriminating colour as the 

 normal. Their trouble was apparently due to their 

 colour-vision being extra sensitive to changes of wave- 

 length in the green part of the spectrum, and not 

 sensitive enough to changes of wave-length in the 

 yellow. — W. Gordon Brown : The Faraday-tube theory 

 of electromagnetism and other notes. The author met 

 his death in France in 19 16 at the age of twenty-one, 

 and these papers were written in 1915-16 while he 

 was convalescing after his Gallipoli experiences. He 

 had just finished school in 1914, ana he joined the 

 Forces immediately war was declared. In the prin- 

 cipal paper he established, on the assumptions of 

 moving tubes of electric force, the equations of the 

 electromagnetic field, and in a shorter quaternion in- 

 vestigation he worked out certain results on the hypo- 

 thesis that the mass operator which changes velocity 

 to momentum is a linear vector function. A few 

 months before his death he was treating the problem 

 of the tubes of force along the lines of the four- 

 dimensional analysis developed by Minkowski, and 

 communicated his results in a letter written to Prof. 

 Whittaker.— T. Bedford Franklin : Some simple e.x- 

 periments on the colloidal content of soils. The 

 mechanical analysis of a soil is no guarantee of its 

 physical behaviour, for although the soil colloids are 

 mainly contained in the finer fractions, yet the col- 

 loidal content of these fractions, as shown by analysis, 

 can vary over a very large range. The paper described 

 simple experiments for estimating the colloidal con- 

 tent. Thus a soil is probably highly colloidal if (i) it 

 takes up a high percentage of water on the dry weight 

 of the soil before reaching "maximum plasticity"; 

 (2) its rate of evaporation declines slowlv with 

 diminishing water content; (3) it freezes well below 

 0° C. ; (4) it takes up, after drying or freezing, much 

 less water before reaching "rnaximum plasticity" 

 than in its natural condition ; and (5) it absorbs and 

 retains for a long time farmyard or artificial manure. 

 Paris. 

 Academy of Sciences, January 30.— M. Emile Berlin 

 in the chair.— C. Lallemand : The comparative advan- 

 tages of the hexagonal abacus and the abacus with 

 aligned points.— C. Moureu and C. Dufraisse : Auto- 

 oxidation. The anti-oxidisers.^ — G. Gouy : The pres- 

 sure in magnetised or polarised fluids. — M. Maurice 

 d'Ocagne was elected a free academician in succes- 

 sion to the late M. J. Carpentier. — T. Varapoulos : A 

 theorem of M. Montel.— .'\. Angelesco : The zeros of 

 certain functions.— A. Cahen : Differential equations 

 of the first order with fixed critical points. — M. Auric : 

 The development as a continued fraction of algebraical 

 numbers.— R. Jacques : Surfaces such that the axes 



