February 25, 191 5] 



NATURE 



719 



with silica either as a silicate or as alkaline auro- 

 silicate. The phenomena, he thinks, demand a single 

 solution from which gold and silica may be precipi- 

 tated simultaneously. — W. G. Holford : Some features 

 in the mining problems of the eastern Witwatersrand 

 area. This paper is a general review of the more 

 intricate geological problems associated with mining 

 in the particular area referred to, where conditions 

 are somewhat different from those met with in the 

 central Rand. For example, while it is found on the 

 central Rand that the close proximity of the zones in 

 which economic gold values are contained are in such 

 close proximity as almost to constitute defined shoots, 

 on the eastern rand the zones are less frequent and 

 are of greater economic value in the synclinal portions 

 of the areas. The author goes on to describe in detail 

 the various features of mining practice in the district 

 under consideration, dealing respectively with mining 

 areas, shaft sinking, initial development, the 

 mechanical equipment, and the labour problems en- 

 countered. Incidentally he makes a strong argument 

 in favour of circular as against rectangular shafts. — 

 W. B. Middleton : Prospecting tin land in Malaya. 

 This is a practical paper concerning itself with the 

 alluvial deposits which are the principal source of the 

 tin production of the Malay Peninsula. The author 

 gives full particulars of the various methods employed 

 in treating, prospecting, and sampling the ground, 

 including an elaborate description of the tools 

 required, and as an appendix he furnishes a set of 

 tables for calculations and conversions in connection 

 with the work, which should prove of great utility. 



Cambridge. 



Philosophical Society, February 8. — Dr. Barnes, vice- 

 president, in the chair. — Sir J. J. Thomson : Theory 

 of the mobility of negative ions. — Dr. G. F. C. Searle : 

 (i) The determination of the focal length of a thick 

 mirror. (2) Experiment on the focal lines formed by 

 refraction at a plane surface. (3) Calculation of the 

 electrical resistance of a certain network of conductors. 

 — C. T. R. Wilson : A method of measuring the thick- 

 ness of thin plates. The method is a modification of 

 that of Mace de Leplnay and Buisson In which /^e, the 

 product of refractive index and thickness, is obtained 

 by measurements of the thin-plate fringes and {u.— \)e 

 by observing the retardation produced by the plate 

 when Inserted in the path of a beam of light. — G. W. 

 White: Investigation of the "wolf-note" in bowed 

 stringed instruments. With all stringed instruments 

 of the violin type a pitch can be found at which It is 

 difficult and often impossible to obtain a pure steady 

 tone. In the preliminary experiments to investigate 

 this imperfect note photographs were obtained of the 

 belly vibration of a 'cello by reflecting a beam of light 

 from an optical lever to a moving photographic plate. 

 A series of notes through the "wolf-note " played wfth 

 a constant bow pressure was studied. At the " wolf- 

 note " the vibration curve had an extremely big ampli- 

 tude and showed that the unsteady nature of the 

 tone was due to a "beating" of the instrument belly. 

 The exp>eriments proved conclusively that the "wolf- 

 note" was caused by the impressed string pitch coin- 

 ciding with the pitch of best resonance of the instru- 

 ment. 



Manchester. 



Literary and Philosophical Society, January 26. — Mr. 

 F. Nicholson, president, in the chair. W. C. Jenkins : 

 Manchester fogs of the last ten years. A comparison 

 of the fogs in Manchester during 1904-1913 inclusive 

 showed that the number of days affected by this pheno- 

 menon has increased during the latter years by at 

 least 30 per cent, as compared with the earlier years 

 of this period. By a rearrangement of the figures 



NO. 2365, VOL. 94] 



into seasonal effects the most striking feature is the 

 increase of days classified as " gloomy " during the 

 summer months, the number during the winter months 

 of October to March remaining fairly constant. The 

 number of days affected by "gloom" increased 100 

 per cent, during the period of the last four years as 

 compared with the number so classified in the first 

 four years of the period under consideration. These 

 fog glooms are situated close to the earth's surface, 

 as is shown by a comparison of sunshine records 

 taken from the roof of the School of Technology and 

 on the ground, the hours of sunshine measured on 

 the ground being approximately 10 per cent. less 

 than the amount recorded from the roof (100 feet 

 higher).— Prof. W. W. Haldane Gee : Note on the 

 monthly variation of sunshine. As a result of his 

 examination of the Campbell-Stokes records, the 

 author found that the average percentage of the pos- 

 sible sunshine usually reaches a maximum in May. 

 A number of examples of this law were quoted. It 

 was true for Glasgow, Douglas (I. of M.), Llandudno 

 and Stonvhurst, 1880-1885 ; for St. Aubins (Jersey), 

 1880-1885"; Blackpool, 1882-1885; Buxton, 1881-1885; 

 Durham, 1880-1884; and for the Godlee Observatory 

 (Manchester School of Technology), 1906- 19 10. The 

 records for Stonyhurst for the thirty-three years from 

 1880-1912 also show the maximum in May. For 

 19 10, Manchester (Oldham Road), Manchester (Whit- 

 worth Park), Buxton, Blackpool, and Llandudno also 

 show the maximum in May. The author thought that 

 the sunlight in May must have an important influence 

 on vegetable growth. — ^W. C. Jenkins : Weather repe- 

 titions, with suggestions for long-distance forecast. 

 Attention was directed to the repetitions in the weather 

 for periods of twelve hours, twenty-four hours, seven 

 days, and the lunar month, and also annual repeti- 

 tions, making certain allowances — using particularly 

 the records of rainfall. With the view of establishing 

 these repetitions to a definite origin, the author 

 showed the connection between numerous cj'clonic 

 paths and extra terrestrial phenomena, and assuming 

 similar forces acting in temperate latitudes, he pro- 

 ceeded to demonstrate that cyclonic movements in the 

 regions of this kingdom followed very much the varia- 

 tions expected under these conditions. 



BOOKS RECEIVED. 



Breeding of Farm Animals. By Prof. M. W. 

 Harper. Pp. xvii + 335. (New York: Orange Judd 

 Co.; London: Kegan Paul and Co., Ltd.) 1.50 

 dollars. 



Practical Physical Chemistrj-. By Prof. A. Findlay. 

 Third edition.' Pp. xvi + 327. (London: Longmans 

 and Co.) 45. 6d. net. 



A Summer on the Yenesei (19 14). By M. D. 

 Haviland. Pp. xi + 328. (London: E. Arnold.) 

 los. 6d. net. 



Board of Education. Examinations in Science and 

 Technology, 1914- Examination Papers and Reports 

 of Examiners. Pp. 142. (London: H.M.S.O. ; 

 Wyman and Sons, Ltd.) gd. 



Alone in the Sleeping Sickness Country. By Dr. 

 F. Oswald. Pp. xii + 219. (London: Kegan Paul 

 and Co., Ltd.) Ss. 6J. net. 



Arabia Infelix, or, the Turks in Yamen. By G. W. 

 Bury. Pp. X4-213. (London: Macmillan and Co., 

 Ltd.) 75. 6d. net. 



The Chemistry of Petroleum and its Substitutes. 

 By Drs. C. K. Tinkler and F. Challenger. Pp. xvi4- 

 352. (London : Crosby Lockwood and Son.) 105. 6d. 

 net. 



