February 3, 19 16] 



NATURE 



641 



•of the diurnal inequality to sun-spot frequency is con- 

 sidered in the light of Wolf's formula, the constants 

 in the formula being determined by least squares. 

 Considerable attention is also paid to the absolute 

 daily range or difference between the extreme values 

 for the day. The frequency of occurrence of ranges 

 •of different size is considered in detail. — G. W. 

 Walker : A portable variometer for magnetic survey- 

 ing. The paper contains an account of a portable 

 magnetic variometer for measuring horizontal force 

 in a magnetic survey. The results obtained with it 

 and with a Kew unifilar at forty-eight stations in the 

 ourse of the magnetic survey of the British. Isles in 

 19 15 are discussed. The operation of measuring force 

 is reduced to a single reading of the instrument, with 

 a reading of the temperature, at a definite instant of 

 time, in place of the elaborate system of readings 

 taking over an hour when a unifilar is used. It is 

 •estimated that the normal error is not likely to exceed 

 57.— Prof. J. C. McLennan: The single-line spectrum 

 of magnesium and other metals, and their ionising 

 potentials. It has been shown that magnesium vapour 

 traversed by electrons can be stimulated to the emis- 

 sion of a single-line spectrum consisting of the wave- 

 length A, = 2852-22 A.U. It has been shown that the 

 absorption spectrum of non-luminous magnesium 

 vapour contains an absorption band at A = 2852-22 A.U., 

 and one at A = 2o73-36 A.U. As the lines A = 285222 

 A.U., and A = 2073-36 A.U., are respectively the first 

 members of the series v = 2,p^-\:^, S, and v—\-s^, 

 S-m, P, respectively, the absorption spectrum of 

 magnesium vapour has been shown to be analogous to 

 the absorption spectra of the vapour of mercury, zinc, 

 and cadmium. The ionising potentials have been 

 deduced for atoms of magnesium, in addition to those 

 for the atoms of mercury, zinc, and cadmium. Con- 

 siderations have also been presented which show that 

 If Bohr's theory affords an explanation of the origin 

 of single-line spectra, then Frank and Hertz and also 

 Newman must have placed a wrong interpretation on 

 the results of their direct investigation of the ionising 

 potentials for mercury atoms. — F. Tinker : The micro- 

 scopic structure of semi-permeable membranes, and the 

 part played by surface forces in osmosis. Micro- 

 photographs of the common precipitation membranes, 

 taken by a new method, show that such membranes 

 are composed of small precipitate particles packed 

 closely together, and ranging from o-i /x to i-o yu in 

 diameter. Each of these precipitate particles is, how- 

 ever, not simple in structure, but is itself an aggre- 

 gate formed by the flocculation of smaller ultra-micro- 

 scopic particles. Of the membranes examined, copper 

 ferrocyanide and Prussian-blue have the smallest par- 

 ticles. Precipitation membranes show most of the 

 physical properties of gels as ordinarily prepared by 

 bulk precipitation, but they have not the same mechan- 

 ical structure as the latter, the membrane having a 

 much finer texture than the gel proper. The pores 

 in a copper ferrocyanide membrane range from 8 yu/x 

 to 60 j«/x in diameter. Their size is such that they can 

 block colloidal molecules mechanically, but not the 

 ordinary crystalloidal molecules even when highly 

 hydrated. The order of a series of membranes with 

 respect to pore size is the same as that of their 

 efficiency as semi-permeable membranes. Copper 

 ferrocyanide and Prussian-blue are the most efficient 

 membranes, and they have also the smallest pores. 

 There is a very close connection between the osmotic pro- 

 perties of a membrane and the extent to which the mem- 

 brane capillaries are under, the control of surface forces. 

 Osmotic effects are probably the result of adsorption 

 phenomena occurring at the surface of the membrane 

 and in the capillaries, the membrane being relatively 

 impermeable to solutes negatively adsorbed, but per- 

 NO. 2414, VOL. 96] 



meable to solutes positively adsorbed. — E. Newhery and 

 J. N. Prlng : The reduction of metaHie .\; 1 - with 

 hydrogen at high pressures. Metallic nvil ■- have 

 been heated to temperatures of 2500 ( . in dry 

 hydrogen at pressures up to 150 atmos|)li< i > s, water 

 vapour being removed by metallic sodium. The fol- 

 lowing oxides were reduced to metals : — 



CrjO, to Cr. MnO^ to Mn. 



The following oxides were reduced to lower oxides : — 



V,0, to VO TiO, to TiO. 



Nb.Os to NbO. CeO, to Ce.O^. 



U,0. to UO,. 

 The following oxides were unchanged : — 



Al,03, MgO, ZrO^, Y,0„ ThO,. 

 The metals obtained, chromium and manganese, are 

 probably, the purest samples of these metals that have 

 been prepared up to the present. This supposition is 

 supported by the sharp nature of their melting points, 

 a feature which has not been observed -with samples 

 prepared by other methods. — H. Levy : Discontinuous 

 fluid motion past a curved boundary. The author 

 considers the regions in the ui( = ^4-t*/') and 

 I2( = log dz/dxf) planes, corresponding to the problem 

 of the discontinuous motion of a fluid in two dimen- 

 sions past a curved boundary, and shows that the 

 problem will be solved if the formulae can be found to 

 transform these regions conformallj' into the same 

 region in a i-plane. This the author succeeds in 

 accomplishing by a synthetic method he has devised 

 — the vectorial superposition of rectangles in the 

 Q-pIane. By this means it is demonstrated that the 

 problem of the impact of a fluid against a boundary, 

 differing by as little as may be desired from a given 

 boundary, may be easily solved. The author pursues 

 in full detail the case of symmetrical surfaces and of 

 plane surfaces with curved ends, A few particular 

 cases are worked out completely. 



Royal Meteorological Society, January 19. — Major 

 H. G. Lyons, president, in the chair. — Major H.G. 

 Lyons : Winter climate of the eastern Mediterranean. 

 During the last fifteen to twenty years a large number 

 of meteorological stations have been in operation, and 

 from their published results we have an accurate and 

 detailed knowledge of the meteorological conditions 

 which prevail there at the different seasons of the year. 

 These vary from the true continental climate of the 

 Balkans, with its low winter temperatures and mode- 

 rate rainfall at all seasons, to the MediteVranean 

 climate of southern Greece and the Levant, with its 

 mild winter, hot summer, and a strongly marked 

 rainy season in winter. In lower Egypt these char- 

 acteristics also prevail in a more intense form. The 

 geographical character of the Balkan Peninsula and 

 the surrounding seas, Syria and Palestine, and lower 

 Egypt, affect to some extent the general climatic 

 conditions. The temperature in the Balkan region in 

 winter is frequently very low, descending to 0° F., 

 and often below this at many stations, while frost 

 occurs often at inland Greece, and occasionally through- 

 out the eastern Mediterranean. January is the coldest 

 month, and February differs but little from it. the 

 first marked departure from winter conditions occur- 

 ring in March. By this month, too, the waters of the 

 Mediterranean begin to grow warmer. In winter rain- 

 fall is heaviest on the western shores of Greece and 

 Syria, and markedly less on the eastern roasts. The 

 Balkan rainfall has a maximum in November and 

 afterwards decreases slightly, but it is not heavy at 

 any time. Rainfall decreases southward, and in lower 

 Egypt the amount is insignificant. Northerly winds 

 which cause rough sea in the /Egean Sea during the 

 winter months are more frequent than southerly winds 

 in the proportion of 2-5 to i. 



