December 28, 1905] 



NA TURE 



215 



give rise to the formation of a scum. Experiments are 

 also described showing that the gas escaping during flota- 

 tion carries an electrical charge, leaving an opposite charge 

 on the solution. The assumption of Messrs. Swinburne 

 and Rudorf of the presence of an air-film on the surface 

 of the sulphide particles is criticised, and it is shown that 

 the particles are floated perfectly after precautions have 

 been taken to remove any adherent film of gas by ex- 

 haustion with acid, washing with alcohol, treatment with 

 air-free distilled water, and exhaustion with the pump. — 

 The ions of pure water : Prof. J. Walker. In the dis- 

 cussion on Dr. Lowry's paper on an application to electro- 

 lytes of the hydrate theory of solution, Mr. Bousfield 

 directed attention to an apparent discrepancy between the 

 temperature coefficient of the mobility of hydrogen and 

 hydroxide ions on the one hand, and the temperature 

 coefficient of the conductivity of water on the other. The 

 author points out that when the data obtained by Kohl- 

 rausch for pure water are employed, and when allowance 

 is made for the temperature coefficient of ionisation, the 

 discrepancy vanishes. 



Geological Society, December 12. — Dr. J. E. Marr, 

 F.R.b., president, in the chair. — The physical history of 

 the great Pleistocene lake of Portugal : Prof. E. Hull. 

 There is evidence that the general level of the lake-bed was 

 once nearly that of the outer sea, and that the sea-waters 

 gained occasional access to the lake during the earlier 

 stage of its formation. The lake was eventually drained 

 by the channel cut by the Tagus at the harbour of Lisbon, 

 upon the elevation of the land to about its present level. 

 — The geological structure of the Sgurr of Eigg : Dr. A. 

 Harker. The conclusions arrived at bring the rock of 

 the Sgurr of Eigg into relation with the other British 

 Tertiary pitchstones, which are all intrusive. 



Manchester. 

 Literary and Philosophical Society, November 28. — 

 Sir W. H. Bailey, president, .in the chair. — Experiments on 

 the variation of the electrical resistance of. osmium with 

 the temperature : H. Morris-Airey. The range over which 

 the experiments were conducted extended from the tempera- 

 ture of liquid air up to dull red heat. The results show 

 that the behaviour of osmium, like that of the ordinary 

 metals, can be represented by a parabolic expression. 



Dublin. 



Royal Dublin Society, November 21. — Prof. W. F. Barrett, 

 F.R.S., in the chair. — Energy of secondary radiation : 

 Prof. J. A. McClelland. This paper is a continuation of 

 previous papers in which the author studied the secondary 

 radiation of /3 particles that is emitted, by substances when 

 acted upon by the rays of radium. The relative intensity 

 of the secondary radiation from a large number of elements 

 for the same incident radiation has been previously 

 measured, the results showing that the secondary radiation 

 is always greater the greater the atomic weight. In the 

 present paper the total energy of the secondary radiation 

 from a lead plate is compared with the energy of the 

 primary radiation that produces it, the plate being thick 

 enough to prevent the transmission, of any radiation; the 

 ratio is found to be 0-62 for lead, and corresponding 

 numbers are given for other elements, the numbers, of 

 course, diminishing with decreasing atomic weight, the 

 number for carbon being oiq. From the known value of 

 this ratio we can calculate theoretically what per- 

 centage of the energy absorbed by any element of the plate 

 is set free again as secondary radiation ; the percentage is 

 as high as 94 for lead and 95 for uranium, with smaller 

 values for lower atomic weights, the percentage for carbon 

 oei ng S3- The importance of this large transformation 

 of the energy of the primary radiation into secondary 

 radiation is shown by some examples. The relation 

 between the coefficient of absorption of the (3 rays and 

 the value it would have if there were no secondary radi- 

 ation is calculated ; for lead one coefficient is about four 

 times the other. Again, when we determine the coefficient 

 of absorption of a radiation by measuring the intensitv 



NO. 1887, VOL. 73] 



after passing through successive layers of a substance, we 

 should, on account of secondary effects, get values of the 

 coefficient diminishing with increased thickness traversed, 

 even if the radiation were perfectly homogeneous. For 

 this reason the $ rays from radium are not so hetero- 

 geneous as they appear to be from observations on absorp- 

 tion. The paper shows how to determine the true 

 coefficient from such observations. — An improved form of 

 entoptoscope for the detection and delineation of cataract, 

 &c. : W. F. Barrett, F.R.S. The author exhibited this 

 instrument, and fully described it with the aid of diagrams 

 and lantern slides. 



Royal Irish Academy, November 30. — Prof. R. Atkinson, 

 president, in the chair. — Second report on Irish cave ex- 

 plorations : Dr. R. F. Scharff, chairman of the com- 

 mittee. Dr. Scharff gave a general survey of the investi- 

 gation, and mentioned that the report embodied the results 

 of the work carried on in the caves of co. Clare during 

 the years 1903-4 under the direction of Mr. R. J. Ussher. 

 The latter subsequently showed a series of lantern slides 

 giving a narrative of the events. Prof. Cole described 

 the geological features. The caves originated by the solvent 

 action of water on the Carboniferous limestone, and may 

 possibly be pre-Glacial. .Mr. Westropp read the portion 

 of the report dealing with the tools and ornaments found, 

 which included chert scrapers, various bone implements, 

 bronze pins, and a beautifully worked bronze buckle, as 

 well as an ancient gold bracelet. Prof. A. F. Dixon dealt 

 with the human remains, while Mr. Newton described the 

 very numerous bird bones, which included those of the 

 crane, now only an extremely rare irregular visitor to the 

 British Isles. The mammalian and other vertebrate and 

 invertebrate animal remains had been determined by Dr. 

 Scharff, who exhibited specimens of the bones and teeth 

 of Irish elk, reindeer, Arctic lemming, Arctic fox, bear, 

 wolf, and Caffer cat, and those of domestic animals, &c, 

 making remarks on their horizontal, vertical, &c, distribu- 

 tion in the caves. — On the former occurrence of the African 

 wild cat (Felis ocreata, Gmel.) in Ireland : Dr. R. F. 

 Scharff. Remains of the wild cat are abundant in the 

 upper stratum of the Clare caves. Careful measurements 

 show that this cat was not the wild cat of Europe (Felis 

 catus), but the African cat (F. ocreata = F. tnaniculata), 

 and that the English cave remains of cat are also mostly 

 referable to the latter species. 



Edinburgh. 



Royal Society, November 20. — Lord McLaren, vice- 

 president, in the chair. — Some further results obtained 

 with the spectroheliometer : Dr. J. Halm. This was a 

 sequel to a previous communication already published in 

 which the main object was to find how Carrington's law 

 of solar rotation varied with the sun-spot cycle. The 

 relative shift of certain solar spectrum lines taken from 

 opposite limbs of the sun was determined by comparing 

 their positions with the positions of neighbouring telluric 

 lines. If, however, instead of the difference of the positions 

 of a chosen solar line the mean be taken, the true position 

 of the solar line referred to the neighbouring telluric line 

 is obtained as it would be were the sun not subject to 

 rotation. Now, according to Doppler's principle, the re- 

 lative position of the solar and telluric lines so determined 

 should be affected by (1) the annual motion of the earth 

 as it recedes from and approaches to the sun ; (2) the 

 diurnal motion of the earth on its axis ; and (3) the swing 

 of the earth about the centre of gravity of the earth and 

 moon during one complete lunation. The amounts of the 

 displacements of the lines in the solar spectrum due to 

 these three motions may be calculated. The monthly 

 motion is too small to be detected with certainty, being of 

 the same order as the errors of observation. The instru- 

 ment was capable of detecting the others. By calculating 

 the diurnal effect and subtracting it from the observed 

 positions, Dr. Halm obtained a distinct annual periodicity 

 in the measured positions of the chosen line, and the 

 observed variation agreed within the errors of observation 

 with the calculated effect. Similarly, subtraction of the 

 calculated annual effect left the diurnal effect clearly marked 



