Page:Nature (v104).djvu/763

26, 1920] February 2.—Sir George A. Berry, vice-president, in the chair.— Dr. C. G. Knott and Miss Dallas: Magnetic strains in nickel-steel tubes. The material was the usual commercial nickel-steel with 2.63 per cent, of nickel. The four tubes were cut down from the same bar, being all of equal length and equal width, and the bores were $$\tfrac{1}{4}$$, $$\tfrac{1}{2}$$, $$\tfrac{3}{4}$$, and 1 in. in diameter. The changes in the length of each tube in various fields were measured, as were also the corresponding changes in volume of the bore of the material and in the external form when the bores were plugged so that the tubes were in appearance solid cylinders; and from these measurements the values of the several lin}ear dilatations in these fields were calculated. The longitudinal dilatation was always positive, attaining a value of from $$3.5\mbox{x}10^{-6}$$ to nearly $$5\mbox{x}10^{-6}$$ in field 500. The corresponding radial and tangential dilatations were negative, and ranged from $$-1.3\mbox{x}10^{-6}$$ to $$-2.4\mbox{x}10^{-6}$$. The results indicate that a spherical element becomes ellipsoidal or spheroidal, with the longest axis along the axis of the tube. If the effect is to be explained in terms of the orientation of magnetic molecules, then these molecules tend to set with their longer axes along the lines of magnetisation. In former experiments with iron and steel the longitudinal dilatation changed sign from positive to negative in fields of about 300 to 400. In nickel, again, the longitudinal dilatation was always negative and about eight or ten times larger than in the case of either iron or steel. In nickel-steel the dilatation remained positive up to the highest fields used (about 900), although in three of the tubes it passed its maximum in field 400 or 500. So far as magnetic strains are concerned, the small admixture of nickel does not impart to the alloy any nickel characteristic whatever.—Prof. W. Peddle: The adequacy of the Young-Helmholtz theory of colour-vision and colour-blindness. Trichromasy in normal eves is not now theoretical, but a proved fact. Hering's theory, which is favoured by some investigators, is, as Helmholtz showed, also a trichromatic theory; and while both can account for the observed facts, the Young-Helmholtz theory is the simplest that can be formulated. Lack of recognition of its accuracy has been due to non-recognition of the fact of normal trichromasy; or to the erroneous supposition that it is tied down to any one definite view of the nature of the physical and physiological actions concerned in vision; or to the equally erroneous supposition that it can account for only one particular type of colour-blindness with merely individual variation<s. It can account for any type that is known, or for any at present unknown which may afterwards be found to exist, provided only that it arises from limitation of the at present known normal conditions.—Prof. W. Peddle; Note on the quaternionic system as the algebra of the relations of physics and relativity. The author showed that in all cases in which our observations are upon directed phenomena occurring in tridimensional space, but which are actually or merely descriptively to be regarded as influenced by the existence of that space in space of a higher order, the appropriate algebra to be used in their investigation is that of Quaternions with the addition of the symbol of the space involved.

Academy of Sciences, February 2.—M. Henri Deslandres in the chair.—The president announced the death of Jules Boulvin, correspondant of the Academy.—C. Moureu and G. Mignonac: The dehydrogenation of the primary and secondary alcohols by catalytic oxidation. A general method of preparation of aldehydes and ketones. Finely divided silver deposited on asbestos was found to be the best catalyst, and the oxidation is carried out in stages, only about half the amount of air theoretically required for the full reaction being employed in the first stage. The results for nine alcohols are given; the yields are high—62 per cent, for formaldehyde and 70 to 95 per cent, for the higher aldehydes.— A. Gantier: The normal arsenic in living tissues and the traces of iodine found in air and waters. Some necessary corrections.— G. A. Boulenger: An extraordinary tortoise, Testudo Loveridgii. This tortoise is the first example of a reptile in the adult state without ribs, and is a unique case of normal osteolysis.— M. Chodat was elected a correspondant for the section of botany in succession to M. Flauhault, elected non-resident "member, and M. Ch. Nicolle a correspondant in the section of medicine and surgery in succession to the late M. Lépine.— L. de Peslouan: A congruence between Bernoulli's numbers.—P. Idrac: Study of hovering flight in Upper Guinea.— M. Romieux: Alluvial strata of the Lot in the neighbourhood of Fumel.— L. Brillouin: The continuous spectrum of X-rays.— F. Canac: The determination of the axes of symmetry of a cubic crystal.—R. Abrard: A Mesoliassic fauna of Sidi Mouley Yakoub (Western Morocco).— F. La Porte: Atmospheric observations at Gâvre by means of free rubber balloons. The experimental results can be fairly well represented by Dines's formula with a modified numerical constant, $$\mbox{V}=\frac{\mbox{oo}\sqrt{\mbox{F}}}{(\mbox{F}+\mbox{P})}$$, where $$V$$ is the ascensional velocity per minute, $$F$$ the ascensional force, and $$P$$ the weight of the envelope in grams.— L. Emberger: The evolution of the chondriome in the vascular Cryptogams.—L. Daniel: Antagonistic reactions and rôle of the pad in grafted plants.— M. Bezssonoff: Experimental sexuality in fungi, situated on the typical structure of the sexual plasma.— F. Gard: Division in Euglena limosa.—G. André: The inversion of saccharose in the juice of the orange.— E. Héronard: Double monsters of the scyphistome.— C. Gessard: Pyocyancid bacilli.

The Topographical Anatomy of the Limbs of the Horse. By Dr. O. C. Bradley. Pp. xi+172. (Edinburgh: W. Green and Son, Ltd.)

Harmsworth's Universal Encyclopedia. No. i. Pp. xix+128. (London: The Amalgamated Press, Ltd.) 1s. 3d.

Index of Economic Material in Documents of the States of the United States. Pennsylvania, 1790–1904. Part i. By A. R. Hasse. Pp. 810. (Washington: Carnegie Institution of Washington.)

Index to U.S. Documents relating to Foreign Affairs. 1828–1861. In three parts. Part ii. By A. R. Hasse. Pp. 795–1331. (Washington: Carnegie Institution of Washington.)

British Journal Photographic Almanac and Photographer's Daily Companion, 1920. Edited by G. E. Brown. Pp. 912. (London: H. Greenwood and Co., Ltd.) 1s. 6d. net.

A Field and Laboratory Guide in Physical Nature-Study. By Prof. E. R. Downing. Pp. 109. (Chicago: University of Chicago Press; London: Cambridge University Press.) 1 dollar net.

Practical Pharmacology: For the Use of Students of Medicine. By Prof. W. E. Dixon. Pp. viii+88. (Cambridge: At the University Press.) 7s. 6d. net.

Chemistry for Textile Students. By B. North. Assisted by N. Bland. Pp. viii+379. (Cambridge: At the University Press.) 30s. net.

An Introduction to the Study of Cytology. By Prof. L. Doncaster. Pp. xiv+280+xxiv. (Cambridge: At the University Press.) 21s. net. NO. 2626, VOL. 104]