July 7, 1923] 



NA TURE 



27 



Two classes of /3-ray tracks are produced in air by 

 the primary action of X-radiation of wave-length 

 less than about 0-5 A: (a) those of ejected electrons 

 with initial kinetic energy comparable to a quantum 

 of the incident radiation, and (&) tracks of very 

 short' range. The short-range electrons are ejected 

 nearly along the direction of the primary X-rays. 

 The short-range tracks are probably related to the 

 phenomena which have led to the postulation of a 

 ' J "-radiation. Of the ordinary long-range tracks, 

 the majority have a large forward component com- 

 parable with the lateral component ; about 20 per 

 cent, are ejected almost exactly at right angles 

 to the primary X-ray beam ; others have a large 

 backward component. Partial polarisation of the 

 primary beams is indicated by the direction of 

 ejection of a number of the /3-particles being in one 

 plane — that containing the direction of the cathode 

 rays in the X-ray tube. j3-rays in air exposed to 

 X-rays frequently occur in pairs or groups. The 

 pairs probably consist of one K electron ejected by 

 the direct action of the primary X-rays, and of a 

 second electron ejected by the combined action of 

 primary radiation and of the K-radiation from the 

 atom from which the first electron was ejected. 

 Pt. II. — /3-rays. The tracks of fast /3-particles are 

 very nearly straight over distances of several centi- 

 metres. Near the end of their range the deviations 

 are of three kinds : [a) sudden deviations often 

 through large angles up to 180°, the results of a close 

 approach to the nucleus of an atom ; (6) sudden 

 deviations ranging up to 45°, due to a close approach 

 to an electron which is in consequence ejected to 

 form a branch track generally approximately at 

 right angles to the deflected primary track ; (c) 

 gradual deviations due to an accumulation of devia- 

 tions of (a) or (6) type. The range of the ;8-ray as 

 measured along the track is approximately pro- 

 portional to the square of the kinetic energy or to 

 the fourth power of the velocity (Whiddington's law) 

 for ranges from about o-i m. to 2 cm. ; the range 

 is I cm. when the kinetic energy of the particle is 

 about 21,000 volts. The primary ionisation (i.e. 

 number of atoms from which electrons are ejected 

 by the direct action of primary ;3-rays) is about 

 90 per cm. for a velocity of 10^" cm. per sec, and is 

 approximately inversely as the square of the velocity. 

 The total ionisation per cm., including that due 

 to secondary /3-particles of range too short to form 

 visible branch tracks, is about three or four times 

 as large as the primary. In portions of some of the 

 tracks not only is the primary ionisation recorded, 

 but also the ions which each of these electrons has 

 itself produced may be counted. — C. V, Raman and 

 K. R. Ramanathan : The molecular scattering of 

 light in carbon-dioxide at high pressures. — W. A. 

 Davis and J. V. Eyre : The discontinuity of the 

 hydration process. — G. M. B. Dobson : A flicker 

 type of photoelectric photometer giving high pre- 

 cision. — H. D. Smyth : The ionisation of nitrogen 

 by electron impact. — G. M. B. Dobson : Measure- 

 ments of the sun's ultra-violet radiation and its 

 absorption in the earth's atmosphere. — H. Hartridge 

 and F. J. W. Roughton : A method of measuring 

 the velocity of very rapid chemical reactions. — 

 W. T. Astbury : The crystalline structure of anhydrous 

 racemic acid. — E. Ponder : The measurement of 

 percentage haemolysis. I. — H. M. Fox : Lunar 

 periodicity in reproduction. — Marjory Stephenson and 

 Margaret D. Whetham : Studies in the fat metabolism 

 of the Timothy grass bacillus. II. Carbon balance 

 sheet and respiratory quotient. — H. R. Hewer : 

 Studies in amphibian colour changes. II. — R. H. 

 Burne : Some peculiarities of the blood-vascular 

 system of the Porbeagle shark {Lamna Cornubica). 



NO. 2801, VOL. I 12] 



— A. E. Boycott and C. Diver : The inheritance of 

 sinistrality in LimncBa peregra. 



Edinburgh. 



Royal Society, May 21. — Prof. F. O. Bower, 

 president, in the chair. — R. Kidston and W. H. 

 Lang : (i) On PalcBopitys Milleri (McNab). The 

 original specimen of this stem with secondary 

 thickening was described by Hugh Miller, and later 

 named by McNab. A second specimen, discovered 

 by the Geological Survey of Scotland, includes the 

 primary central region, 1-5 mm. in diameter, sur- 

 rounded by a zone of secondary xylem about i cm. 

 thick. The secondary wood consists of tracheides 

 and medullary rays. The tracheides are remarkable 

 in having multiseriate, porose pitting on both radial 

 and tangential walls. Tne primary central axis 

 appears to have consisted of tracheides without 

 admixture of parenchyma. There is evidence of 

 strands of protoxylem, consisting of narrow spiral 

 tracheides, close to the periphery of the primary 

 xylem, just within the secondary wood. In the 

 absence of any traces going to lateral appendages it 

 is impossible to determine the affinities of this 

 complex stem. It might have belonged to some 

 gymnospermous plant, but it is equally possible that 

 it was the stem of some archaic pteridophyte of the 

 Middle Old Red Sandstone Period. (2) Notes on 

 fossil plants from the Old Red Sandstone of Scot- 

 land. I. Hicklingia Edwardi, K. and L. Under this 

 name a unique specimen of a Middle Old Red Sand- 

 stone plant is described and figured. It was discovered 

 many years ago by the late Mr. G. Edward, and is 

 preserved in the University of Manchester Museum. 

 It occurs as an incrustation, and suggests comparison 

 with a plant of the nature of the Rhyniaceae spread 

 out on a slab of Caithness flagstone. Diverging from 

 an obscure basal region is a tuft of linear axes, with- 

 out leaves, but branched dichotomously and later- 

 ally. There are indications of the presence of a 

 slender central strand. Many of the stems terminate 

 in oval carbonised bodies that are evidently large 

 sporangia. The plant is compared with Rhynia and 

 Hornea, which are known as petrifactions from the 

 Rhynie Chert.— W. T. Gordon: The genus Pitys. 

 Fossil trees belonging to this genus have been known 

 since 1831, and it was in describing these specimens 

 that thin sections of fossil wood were first used. A 

 recent discovery at Gullane has disclosed twigs and 

 stems of this type, in some cases still clothed in 

 bark and in two specimens with leaves attached. 

 These leaves resemble petioles in their structure, and 

 are undoubtedly phyllodes. Pitys dayi affords evi- 

 dence of the phyllode theory of leaf formation in 

 gymnosperms. Pitys shows marked resemblance to 

 Araucaria as regards the structure of the wood (recog- 

 nised long ago) and the leaf- traces and leaves. 



Paris. 



Academy of Sciences, June 11. — M. Albin Haller in 

 the chair. — Edouard Imbeaux : The artesian basins 

 of Australia. A map of Australia is reproduced 

 showing the artesian basins known at the present 

 time, taken from the report of the interstate con- 

 ference on artesian water held at Adelaide in 1921. — 

 M. Jean Perrin was elected a member of the section 

 of general physics in succession to the late M. E. 

 Bouty. — Paul Montel : Algebraic relations of class 

 one or zero. — Rene Gamier : Uniform functions of 

 two independent variables defined by the inversion 

 of an algebraic system to total differentials of the 

 fourth order. — Charles N. Moore : The summability 

 of Cesaro for double Fourier's series. — Louis Bachelier : 

 The general problem of discontinuous statistics. — 



