462 



NATURE 



[February 2, 191 1 



material containing ions of both kinds acts by induction. 

 The effect of such induction would primarily be an increase 

 in the horizontal and a diminution of the vertical forces, 

 while the currents induced in the earth, tending to 

 diminish the horizontal forces, would, owing to their inertia, 

 die out more slowly, so that a semi-permanent effect would 

 be left after the storm. This agrees with observation, 

 but there are at present not enough data available to 

 test the sufficiency of the explanation. — Arthur Schuster : 

 The periodicity of sun-spots. In this communication, the 

 sun-spot records of the last ten years are discussed in so 

 far as they have a bearing on the results previously sub- 

 mitted to the society. It appears that the period of 479 

 years discovered by the author is confirmed, but that the 

 evidence does not support the periodicity of 4-38 years, 

 which had been previously described as doubtful, nor that 

 of 8-36 years, which during the first half of last century 

 seemed active. Attention is directed to the independent 

 discovery of the period of 4-79 years in the declination 

 range of the magnetic needle at Munich by Mr. Oppen- 

 heim. — Dr. G. C. Simpson and C. S. Wrigrht : Atmo- 

 spheric electricity over the ocean. This paper contains 

 the results of observations made on the voyage . from 

 England to New Zealand on Captain Scott's .Antarctic 

 ship the Terra Nova. The investigation is divided into 

 four parts. The first part deals with the electrical 

 potential-gradient over the ocean. It is found that the 

 gradient has its chief maximum in the evening and its 

 chief minimum soon after midday. The afternoon mini- 

 mum is remarkable because, though observed at many 

 stations on land, it has often been ascribed to the dis- 

 turbing effect of dust. In view of the present results, this 

 explanation does not seem correct. The minimum, which 

 is observed at 4 a.m., and which has been considered the 

 principal one in observations taken on land, is only feebly 

 developed at sea. The numerical value of the potential- 

 gradient was found, on the average, to be about 80 volts 

 per metre, and is therefore approximately the same as 

 that observed on land. The second part of the investiga- 

 tion deals with the quantity of radio-active products which 

 are found in the air. The observations show that these 

 products are decidedly fewer at sea than on land, and a 

 specially low value, both north and south of the equator, 

 is found in latitudes from 30° to 40°. This is ascribed 

 to the fact that the air in these latitudes is supplied by 

 pure air descending from the upper parts of the atmo- 

 sphere, while it is mainly the air which has passed over 

 land which carries radio-active products with it. In the 

 third part of the investigation, the number of free ions 

 in the air are measured, and here again it is found that 

 the ionisation over the sea is smaller than that over land. 

 In the concluding part of the paper the spontaneous ionisa- 

 tion in a closed vessel is measured. Though part of the 

 effect is ascribed to a real effect of air becoming conduct- 

 ing by itself, some of the results obtained indicate clearly 

 that when the ship near land was exposed to radio-active 

 emanation, the observed ionisation showed an increase for 

 several hours afterwards. — Dr. W. H. Young : The 

 Fourier constants of a function. In this paper the possi- 

 bility of treating the Fourier series of a function f{x) in 

 various circumstances, as if it were convergent and 

 integrable term by term, when multiplied by another 

 function, is illustrated by the application of this fact to 

 the determination of expressions for 1a„n~'i anH '%h„n~'>, 

 a„ and hn denoting the Fourier coefficients of /(.r), and 

 q having a non-negative value. The formulae are shown 

 to be valid for any function that has bounded variation 

 in an interval containing the origin, and is elsewhere sum- 

 mable, provided only that q is greater than zero. — J. A. 

 Crowther : The energy and distribution of scattered 

 Rontgen radiation. Experiments have been made to deter- 

 mine what fraction of the incident radiant energy is 

 scattered per unit mass of a radiator when primary 

 Rontgen rays fall upon it. From the numbers obtained a 

 value has been deduced for the number of electrons per 

 atom of the radiating substance. The value obtained 

 agrees closely with that previously deduced from experi- 

 ments on the scattering of homogeneous $ rays, being very 

 nearly three times the atomic weight of the substance. 

 The distribution of the scattered radiation has been 

 measured. It reaches a maximum forwards and back- 

 wards along the line of the primary beam, and falls to a 

 NO.. 2153., VOL. 85] 



minimum at right angles to this direction. At an\ 

 angle with the primary beam there is always a preiKHJw , - 

 ance of scattered radiation in the forward direction. Thi- 

 preponderance increases the more nearly we approach th>' 

 line of the primary beam. — Mrs. Hertha Ayrton : Some 

 new facts connected with the motion of oscillating water. 

 The author's explanation of the origin of ripple-formin 

 vortices having been contested, she has made further 1 

 periments to prove the two propositions on which it rest, 

 viz. that when water oscillates over a submcrgi d 

 obstacle : — (1) during the whole of any single swing .1 

 diminution of pressure is established close to the uppi r 

 part of the lee side of the barrier ; (2) while the wav r 

 is falling below the mean level, in the half of the troui 

 where the obstacle is, there is a back pressure against i 

 flow on its lee side below the area of diminished pressiu 

 Experimental proof of these pressure conditions is gi\ 

 by means of an obstacle in the form of a hollow wat< 

 tight box, of which the top and one side are covered wiih 

 thin guttapercha tissue diaphragms, the air being expelled 

 and the box partly filled with water. These pressure con- 

 ditions cause a jet to flow down close to the lee side of an 

 obstacle during the first part of a swing, and a vortex to 

 form during the second by upsetting the equilibrium of 

 water, in the lee of the obstacle, that would otherwi- 

 remain at rest. The back pressure extends only to t' 

 limits of this slack water, i.e. to the line where the low 

 water flowing over the obstacle strikes the bottom. A 

 trough with an artificial end fitted with diaphragms is 

 used to show that such pressure conditions are not con- 

 fined to submerged obstacles, but come into existence clo>'; 

 to any solid where water, in oscillating, is moving away 

 from it, and wherever two masses of water are flowing 

 away from one another, as at the node of a stationary 

 wave. These variations of pressure give rise to jets and 

 vortices near the surface of oscillating water wherever it 

 meets the end of a vessel, and at every node ; it is these 

 jets and vortices, and the streams that feed them, that 

 cause the residual whirls previously found by the author 

 in oscillating water. The most important proof of this is 

 that when the trough is rocked, so that there is much 

 bottom motion but very little rise and fall, and, conse- 

 quenth', only feeble jets and- vortices, the author's residual 

 whirls are insignificant, while Lx>rd Rayleigh's, beneath, 

 develop to their full length and height even in deep water. 



Geological Society, January 11. — Prof. W. W. Watts, 

 F.R.S., president, in the chair. — Miss G. R. Watney and 

 Miss E. G. Welch : The zonal classification of the 

 Salopian rocks of Cautley and Ravenstonedale. The dis- 

 trict described lies north-east of Sedbergh and west of 

 the Dent fault. Below are Valentian rocks (A and B 

 divisions of the Stockdale shales). The Wenlock beds are 

 most fully developed in some streams entering the river 

 Rawthey from the south. The detailed succession of these 

 is given, and confirmatory sections are described in other 

 parts of the district. The Ludlow beds are found mainly 

 in the northern part of the area, where the geology is 

 simpler. A comparison is instituted between these beds 

 and those in the Welsh borderland, and those of Wenlock 

 age in southern Sweden. A description of a Cyrtograptus 

 intermediate in character between C. rigidus and C. 

 symmetricus, and of a new Monograptus from the Nilssoni 

 beds of Wandale Hill, is given in a palaeontological 

 section. — Herbert Bolton : A collection of insect remains 

 from the South Wales Coalfield. Nine examples of insect 

 remains, all, with one exception, blattoid in character. 

 Seven are described as new species. The insect remains 

 are referable to three horizons, one at the base of the 

 upper series of the Coal Measures, and two in the upper 

 part of the Pennant series. The suggestion is put for- 

 ward that possibly Carboniferous cockroaches were not 

 only phytophagous in habit, but frequented decaying 

 Cordaites leaves in order to feed upon the Spirorbis. The 

 presence of archimylacrid and orthomylacrid forms is 

 considered indicative of an advance in insect develop- 

 ment in the British Carboniferous beyond the palsEO- 

 dictyopteran types, while their abundance in the Pennant 

 and upper series of the South W'ales Coalfield may justify 

 the hope of finding more primitive forms at a lower 

 horizon in the same coalfield. 



