June 9, 1921] 



NATURE 



477 



ironstone "pans " of the reef, but usually pass down- 

 ward by gritty intercalations into the glauconitic 

 loams. The incoming of the Upper Gault, with keeled 

 ammonites, is shown in three of the sections. A 

 band of corroded phosphatic nodules, like those of the 

 "Junction-Bed " at Folkestone, occurs near the base 

 of the division, and marks a long pause in the sedi- 

 mentation. This band has yielded many fossils. The 

 palaeontology of the deposits is discussed, and is held 

 to be in general agreement with that of the same 

 succession in northern France. 



Physical Society, May 27. — Sir W. H. Bragg, presi- 

 dent, in the chair. — H. Pealing : The reflection of the 

 X-ray spectrum of palladium from fluorspar. An 

 examination of the odd order spectra reflected from 

 the 100 plane of fluorspar, using palladium X-rays, 

 has been made with the view of testing the Lewis- 

 Langmuir theory of the motion of valency electrons 

 in compounds. Evidence in partial confirmation of 

 the theory has been obtained.— Sir VV. H. Bragg : 

 The intensity of X-iav reflection by diamond. The 

 relative intensities of the reflections of monochromatic 

 X-rays bv the crystallographic planes of diamond are 

 given. The special difficulties due to the small size 

 of available crystals are discussed. The results lie 

 very closely on smooth curves, indicating that if the 

 outer electrons of the carbon atom lie at any con- 

 siderable distance from the centre they must be in 

 motion over a wide range, or for some other reason 

 must contribute little to the reflection. The properties 

 of the carbon atom In diamond are based on a tetra- 

 hedral form. The tetrahedra point away from any 

 (ill) plane in the case of half the atoms, and towards 

 it in the case of the other half. Consecutive 1 1 1 

 planes are not exactly of the same nature, and con- 

 sequently some slight second-order reflection from 

 the tetrahedral plane might be expected. This effect, 

 though slight, has been found. — Research Staff of the 

 General Electric Co., Ltd. : A method for the micro- 

 analysis of gases by the use of the Pirani pressure 

 gauge. A method of analysis of gases at a pressure 

 between 061 and 0001 mm. is described, based on 

 the characteristic vapour-pressure temperature curve 

 of any substance. A gauge such as the Pirani gauge, 

 which will measure the pressures of vapours, as well 

 as of permanent gases, over the range mentioned is 

 used. 



Manchester. 



Literary and Philosophical Society, Februarv 8. — Sir 

 Henry A. Miers, president, in the chair. — C. W. 

 Duckworth : Note on a unique set of hydrometers. — ■ 

 Prof. G. Unwin : Samuel Oldknow, the first manu- 

 facturer of British muslins. An account of Oldknow 's 

 records (1782-1812), including the whole process of 

 manufacture. 



Literary and Philosophical Society and the Faraday 

 Society (Joint Meeting), Februarv 11. — Prof. A. W. 

 Porter, president of the Faraday Society, in the chair. 

 — Dr. A. Ferguson : Studies in capillarity. Part i. : 

 Some general considerations, and a discussion of the 

 methods of measuring interfacial tensions. The im- 

 portance of accurate measurements of surface ten- 

 sions, in view of the development of colloid physics. 

 Is becoming Increasinglv manifest, and a systematic 

 determination of caplllarv constants is urgently 

 needed. In this paper the "genetic" relations of 

 various methods for the measurement of surface 

 tensions are discussed. A critical comparison of these 

 shows that among the most promising methods for 

 systematic use are those depending on the measure- 

 ment of (i) large bubbles or drops, (2) the maximum 

 pressure required to release a bubble of air from the 

 end of a capillary tube Immersed in the liquid, and 

 NO. 2693, VOL. 107] 



(3) the maximum pull on an anchor ring which is 

 Immersed In the liquid and slowly withdrawn. Deal- 

 ing with the ascent of a liquid in a capillary tube, it 

 is shown that where or is the specific cohesion and h the 

 height to which the liquid rises in a tube of radius r, 

 the equation 



2a' = rh{ I + rh '3 - o- 1 288 r 7i') 



Is adequate for all requirements. Methods are pro- 

 posed for the measurement of the surface tensions of 

 such liquids as molten metals, and the problem of the 

 accurate measurement of Interfacial tensions is dis- 

 cussed. — Dr. A. Ferguson and P. E. Dowson : Studies 

 in capillarity. Part II. : A modification of the capil- 

 lary tube method for the measurement of surface ten- 

 sions. A modification of the usual method is pro- 

 posed In which the meniscus is forced down to the 

 end of the capillary immersed v'ertlcallv in the liquid, 

 and the pressure required to effect this is measured 

 on a separate manometer. Apart from small correc- 

 tions, the difference In level of the surfaces of the 

 liquid In the gauge is equal to the heights to which 

 the same liquid would rise In the capillary tube em- 

 nloved. By using a specially light liquid in the gauge 

 this difference mav therefore be magnified. But any 

 manometer of sufficient delicacy mav be used and the 

 use of a cathetometer avoided. Thus the differential 

 manometer or a simple sloping-tube manometer will 

 give accurate results by ordlnarv naked-eye estima- 

 tions. Temperature control becomes relativelv simple, 

 and the temperature of the meniscus mav be estimated 

 by means of a thermo-junctlon placed close to the 

 end of the tube. Calibration of the capillary is un- 

 necessarv, for measurements are always made with 

 the meniscus in one definite position — at the end of 

 the tube. 



Dublin. 

 Royal Dublin Society, >Liv 24.— Dr. F. E. Hackett 

 In the chair.— Prof. T. Johnson and Miss J. G. Gil- 

 more : The occurrence of Dewalquea In the core of ^ 

 the bore made at Washing Bav, Co. Tyrone. This 

 bore, made to tap a concealed coalfield if possible, 

 had to be abandoned owing to the unexpected thick- 

 rtess of the bed of Lough Neagh Clay encountered 

 (1196 ft. instead of 250 ft.), and from other causes. 

 Plant-remains were obtained, especially at a depth of 

 870-030 ft., above the lithomarg^' or basalt. The 

 hellebore-like foliage of Dewalquea was found repre- 

 sented by three new species, D. hibernica, D. fraxini- 

 folia, and D. denticulata, of which particulars are 

 g-jven. The authors restored the leaves and found peltate 

 scales, like those of Engelhardtia, present. They regard 

 Dewalquea as an ancient member of the Tuglandaceae. 

 It is recorded from the Cretaceous of America and 

 Europe, also from Belgium (Lower Eocene) and Italy 

 (OHgocene). The plant-beds at Washing Bay are 

 probablv Upper Oli^ocene. — The late Prof. J. A. 

 McClelland and J. T. McHenry : Uncharged nuclei pro- 

 duced in moist air by ultra-violet light and other 

 sources. The uncharged nuclei produced in moist air 

 bv ultra-violet light were given an electric charge 

 through the agency of uranium. Their number and 

 size could then be readilv found under varving condi- 

 tions. It is concluded that they are minute drops of 

 water, and that they probably owe their formation to 

 the production of hvdrogen peroxide. The nuclei pro- 

 duced by heating glass were also studied. Moderate 

 heating caused a temporarv evolution of nuclei, attri- 

 buted to surface Impurities absorbed from the atmo- 

 sphere. Strong heating caused a continuous evolution, 

 attributed to disintegration of the glass. Similar effects 

 were observed with metals.— H. G. Becker : A simple 

 apparatus for observing the rate of reaction bet^^een 

 gases and liquids, and the determination thereby of 



