4/8 



NATURE 



[June i6, 1910- 



«nergy of the oscillatory current through the contact is 

 transformed into heat at the contact and warms the matter 

 there sufficiently to change its electrical resistance, and, 

 •consequently, the steady current through the indicating 

 instrument. The experiments are on a detector of the so- 

 called " crystal rectifier " type, from which, however, the 

 possibility of thermoelectric effects has been eliminated. — 

 S. W. J. Smith : The limitations of the Weston cell as 

 a standard of electromotive force. The experiments of Mr. 

 F. E. Smith on cadmium amalgams are discussed. Theory 

 and experiment suggest that there is no range at any 

 temperature over which the E.M.F. of a Weston cell is 

 absolutely independent of the percentage of Cd in the 

 amalgam. Even if the materials are pure, the existence 

 of surface energy must cause some variation. Within the 

 range over which the E.M.F. is usually taken as constant 

 the E.M.F. appears to rise, very slowly, with increase in 

 the cadmium content. The rate varies, but is never more 

 than a few millionths of a volt for i per cent. Cd. From 

 •the data it seems possible also to discover the precise way 

 in which the use of the richer two-phase amalgams may 

 lead to variability of the E.M.F. of the Weston cell. The 

 interpretation advocated is that the irregularities are due 

 to electrolytic skin effects arising out of want of uniformity ' 

 of composition of the surface grains. The probable reason i 

 why the temperature coefficient of E.M.F. of a Weston j 

 cell, always small, actually vanishes near o° C. is indicated. 



Ge .logical Society, May 25. — Prof. W. W. Wati-s I 

 F.R.S., president, in the chair. — Dr. F. H. Hatch and 

 K. H. Rastall : Dedolomitisation in the marble of Port 

 Shepstone (Natal). The Port Shepstone marble is shown 

 by chemical analysis to be a dolomite. It owes its 

 marmorisation to thermal metamorphism by an intrusion 

 of granite, which surrounds it and penetrates it in broad 

 ■dykes. This intrusion took place at some time prior to 

 the deposition of the Table Mountain or Waterberg Sand- 

 stone, and is therefore pre-Devonian. The metamorphism 

 •of the dolomite under normal conditions produced a 

 saccharoidal marble of coarse texture, consisting of 

 carbonates ; and the fact that neither periclase nor brucite 

 has been produced in the normal marble is taken to indicate 

 that the high-pressure conditions obtaining during the meta- 

 morphism precluded dedolomitisation. — E. B. Bailey : Re- 

 cumbent folds in the Highland schists. A description is pre- 

 sented of the stratigraphy and structure of a portion of the 

 Inverness-shire and Argyllshire Highlands. The district 

 (Considered lies south-east of Loch Linnhe, and extends 

 from the Rfver Spean in the north to Loch Creran in the 

 south. The following conclusions are arrived at : — (i) The 

 -schists of the district are disposed in a succession of re- 

 cumbent folds of enormous amplitude — proved in one case 

 to be more than twelve miles in extent. (2) The limbs 

 of these recumbent folds are frequently replaced by fold- 

 iaults, or " slips," which have given freedom of develop- 

 ment to the folds themselves. (3) The slipping is not con- 

 fined to the lower limbs of recumbent anticlines, and is 

 •due to something more than mere overthrusting. It is a 

 complex accommodation phenomenon. The cores of some 

 of the recumbent folds have been squeezed forward, so that 

 they have virtually reacted as intrusive masses. . (4) In 

 ■ the growth of these structures many of the earlier formed 

 cores and slips have suffered extensive secondary corruga- 

 tion of isoclinal type. 



Linnean S'^rietv. lurp 2. — Dr. D. II. Scott, F.R.'^.. 

 president, in the chair. — Dr. A. B. Rendle and others : 

 A contribution to our knowledge of the flora of Gazaland : 

 an account of collections made by Mr. Swynnerton, by 

 members of the Department of Botany, British Museum, 

 with notes by Mr. Swynnerton. The collections which form 

 the subject of this paper were made by Mr. C. F. M. 

 Swynnerton chiefly in the high country which forms the 

 boundary between eastern Rhodesia and Portuguese terri- 

 tory. It consists of a number of detached masses of high- 

 land separated by river valleys which ultimately unite to 

 form the Buzi, an important river running eastwards 

 through the lower-lying Portuguese territory to enter the 

 Indian Ocean near Beira. Mr. Swynnerton has supplied 

 :an interesting account of the phyto-geographical character 

 •of the district. There is evidence that it was once covered 

 with dense forest, which has, however, been largely 



NO. 2120, VOL. 'i^^ 



destroyed by the annual forest fires during some formi 

 period of dense population. At present the forest occupi 

 the more protected uplands, forming great patches ; siu 

 ar-^ the great forests in the Chimanimani mountains in tl 

 north, a rugged range reaching a height of 8000 feet, ar 

 the Chirinda and Chipete forest patches closely adjoinii 

 each other in the south. Chirinda is described as a vii^ 

 forest of enormous, and mostly evergreen, trees, coveni 

 about 12,000 acres of the higher portions of the hill. I 

 larger trees range from 80 to 170 feet in height, and tl 

 undergrowth, with mosses, ferns, epiphytes, and lianas, 

 of a thoroughly tropical character. As was to be expecb 

 from the geographical position, the botany of these hig 

 lands shows a strong South African affinity, and sever 

 of the genera and a considerable number of the sped 

 have not been hitherto recorded beyond South Africa, 

 large proportion of the plants are identical with tho 

 previously known from Nyasaland. There is also a we 

 marked Angolan element. An interesting novelty 

 Pseudocalyx africanus ; Pseudocalyx is a Malagasy gen' 

 not hitherto known from tropical Africa. 



Mathematical Society, June 9. — Sir Wm. Nive 

 president, in the chair. — G. T. Bennett : The compositit 

 of finite screw displacements. — Prof. M. J. M. Hil 

 Differential equations with fixed branch points. — Miss I 

 Long : Geiser's method of generating a plane quart 

 curve. — ^W. P. Milne : The generation of cubic curves 1 

 apolar pencils of lines. — E. Cunningrham : The cons' 

 tutive equations of material media in electrodynamics.- 

 Dr. W. H. Youngr : (i) A new method in the theory 

 integration ; (2) semi-integrals and oscillating successio 

 of functions. — H. R. Hassd : The transformation of t! 

 equations of the theory of electrons for quasi-stationa 

 motion. 



Edinburgh. 



Royal Society, May 2. — I'rof. Hudson Beare, vit 

 president, in the chair. — Sir Joseph Larmor : Address < 

 the dynamics of molecular diffusion, with extension 

 suspended particles. After referring to the remarkat 

 parallelism between the phenomena of a free gas, of spar 

 molecules constituting a dilute solution in water or oth 

 fluid, and of the Brownian movements. Sir Joseph pr 

 ceeded to emphasise the distinction between osmol 

 pressure and gas pressure. The former depended on t' 

 frictional pull of moving particles, and the latter on t 

 momentum of the free motion. The zigzag paths 

 particles suspended in water, photographs of which we 

 projected on the screen, suggested that here also, as 

 gases, there was an average free path and an avera, 

 speed to which the power of diffusion stood in defini 

 relations. In this discussion the unexpected resi 

 emerged that, at the same temperature, the mean spe 

 was proportional to the number of particles in suspensio 

 Recent observations under the ultra-microscope, by whii 

 we can detect particles of a size more minute than can 

 seen by direct optical methods, have not contradicted tf 

 conclusion. The analogy between free gases and dilu 

 solutions must not therefore be pressed too far. There w 

 ground for thinking that we were approaching a gre 

 advance in the interpretation of phenomena of this kin 

 namely, the average phenomenon of a great crowd^ 

 molecules as they affect en masse our senses of perceptio 

 The main interest and fascination of science lay in i 

 growing points where new knowledge was gaining groui 

 on the unknown ; and to consider some of the rer 

 achievements and the outstanding problems in a field n 

 rapidly undergoing development seemed more suitable 

 such an audience as the Royal Society of Edinburgh th 

 to pass under review once more some harvest alrep 

 definitely won and safely garnered in the stores of hun 

 knowledge. 



May 16. — Prof. Crum Brown. F.R.S., in the chai: 

 J. W. M'David : Equilibrium in the ternary system, wa; 

 potassium carbonate, potassium ethyl di-propylmalona' 

 Crichton had observed that when a concentrated aqueo 

 solution of this last-named salt was shaken up with 

 concentrated solution of potassium carbonate, two dist^ 

 layers were formed. The object of the present paper '> 

 to' show how the miscibility of the two solutions depend 

 on their concentration, temperature, &c. Various solutio 



