598 



NA TURE 



[April 21, 1892 



the outlines of the structure have for the most part become 

 obliterated by molecular changes, and the limestones are often 

 rendered crystalline Tn connection with this the author alludes 

 to the disturbances which have affected the limestones. He 

 finds occasional rhombohedra of dolomite, and discusses the 

 probability of their derivation from magnesian silicates contained 

 in ihe roci<s. A description of the insoluble residues follows. 

 The micas, the author considers, may be of detrital origin, but 

 this is by no means certain ; he is disposed to consider that the 

 zircons, tourmaline, and ordinary rutile were liberated by the 

 decomposition of crystals in which they were originally included. 

 Minute crystals, referred to as "microlithic needles," resemble 

 "clay-slate needles," but are not always straight : they occur 

 in every fine residue, and as inclusions in siliceous and micaceous 

 flakes. The siliceous fragments which inclose them frequently 

 contain many liquid inclusions, which does not necessarily 

 imply any connection between the two, though there may 

 possibly he some connection. Micro-crystals of quartz occur, 

 and have been derived from decomposing silicates. The reading 

 of this paper was followed by a discussion, in which Dr. Sorby, 

 Prof. Bonney, Dr. Hicks, Prof. Rupert Jones, the President, 

 and others took part. 



April 6.— W. H. Hudleston, F.R.S., President, in the 

 chair. — The following communications were read : — Geology 

 of the gold-bearing rocks of the Southern Transvaal, by 

 Walcot Gibson. The author describes the general character- 

 istics of the rocks of the Southern Transvaal, and gives a sum- 

 mary of previous work on the area ; he then discusses the 

 physical relations of the gold-bearing conglomerates and asso- 

 ciated rocks in the Witwatersrandt district, and describes the 

 various rocks in detail. He concludes that the gold-bearing 

 conglomerates and the quartzites and shales of the Witwaters- 

 randt district (which have undergone considerable metamorphism) 

 form one series, of which the base and summit are not seen ; 

 that this series is much newer than the gneisses and granites on 

 the eroded edges of which they rest, and older than the coal- 

 bearing beds which unconformably overlie them ; that the entire 

 series associated with the gold-bearing beds has been thrust over 

 the gneisses, and was not originally deposited in its present 

 position, the movements having taken place in two directions, 

 viz. from south to north and from east to west ; that, after the 

 cessation of these movements, the strata were injected with basic 

 and sub-basic igneous material, and much of the country was 

 flooded with lavas of the same character ; and that the conglo- 

 merates have been formed mainly at the expense of the under- 

 lying granites and gneisses, which were largely threaded with 

 auriferous quartz-veins and contained larger masses of quartz. 

 The author then describes the geology of districts outside the 

 typical area, which, though at first sight more complex, are 

 really simpler than that of the typical area. The conclusions 

 arrived at from an examination of these areas confirm the results 

 of the study of the rocks of the Witwatersrandt district. The 

 reading of this paper was followed by a discussion, in which 

 the President, Prof. Green, Mr. Attwood, Mr. Topley, Mr. 

 Alford, Prof Lapworth, and Mr. Teall took part. — The 

 precipitation and deposition of sea-borne sediment, by R. G. 

 Mackley Browne. The author discusses the mode of deposition 

 of current-borne sediment upon the ocean-floors, and considers 

 the effects of current-action in sifting the material and causing it 

 to accumulate into stratified linear ridges having directions 

 generally parallel with those of the currents — the dip of the 

 strata varying according to the velocity of the currents. He 

 considers that the conclusions deducible from his analysis ap- 

 pear to be in accord with the evidence afforded by the structure 

 of ancient subaqueous sedimentary deposits. 



Linnean Society, April 7.— Prof. Stewart, President, in 

 the chair. — Mr. Spencer Moore exhibited and made remarks 

 upon some samples of Mate or Paraguayan tea recently 

 brought by him from South America.— Mr. J. Tristram Valentine 

 exhibited a skin of Grevy's Zebra, recently brought from Somali- 

 land by Mr. H. D. Merewether, who had purchased it from a 

 caravan arriving from the Southern Dolbahanta country, to the 

 south-east of Berbera. Although it corresponded in the character 

 and disposition of the stripes with the type specimen from Shoa, 

 and with a skin in the British Museum from Berbera (P. Z.S., 

 1890, p. 413), it differed in the stripes being brown upon a pale 

 sandy or rufescent ground, instead of black upon a white ground. 

 It was suggested that this might be the desert form, the type 

 specimen representing the mountain form. — Mr. Tristram 

 Valentine also exhibited horns of Swayne's Hartebeest and 



NO. II 73, VOL. 45] 



Clarke's Antelope (both recently described species), which, like 

 the Zebra skin, had been lately brought from Somali-land by 

 Mr. Merewether. — Mr. W. S. D'Urban exhibited specimens of 

 the shell-slug Testacella maugei from Devonshire. — A paper was 

 then read by Mr. D. Morris, on the ])henomena concerned in 

 the production of forked and branched palms, the conclusions 

 arrived at being the following: — (i) Branching is habitual in 

 certain species oi Hyphcene ; occasional in others, and occasional 

 also in the genera Areca, Rhopalostylis, Dictyosperma, Oreo- 

 doxa, Leopoldinia, Phoenix, &c. (2) Branching in many cases 

 results from injury to or destruction of the terminal bud, causing 

 the development of axillary or adventitious buds below the apex : 

 these buds when lengthened out produce branches. (3) In some 

 cases, as in Nannorhops ritchieana and Phcenix sylvestris, 

 branching is caused by the replacement of flowering buds by 

 branch buds. In such cases the branches are usually short, and 

 are arranged alternately along the stem. The terminal bud 

 is apparently neither injured nor destroyed. — A paper by Mr. 

 A. W. Waters, on the gland-like bodies in the Bryozoa, was, in 

 the absence of the author, read by Mr. W. Percy Sladen. 



Dublin. 

 Royal Society, March 16.— Prof, W. Noel Hartley, F.R.S., 

 in the chair. — Prof. Haddon presented a paper by Prof. 



F, Jeffrey Bell on the Echinoderms collected during the 

 Society's fishery survey of the west coast of Ireland. Psolus, 

 sp. juv., was recorded for the first time from Ireland (500 

 fathoms), Astropecten sphenoplax, n. sp. (500 fathoms). Amongst 

 other rarities Asthenosoma hystrix was largely represented ; the 

 specimens differ so much that were it not for intermediate forms, 

 more than one species might be described. Prof. Bell proposes to 

 regard A. {Calveria) fen e stratum as a synonym of A. hystrix. — 



G. Johnstone Stoney, F. R.S., read a paper entitled " Proposed 

 Standard Gauge, to help in appreciating the small ultra-visible 

 quantities that have to be taken into account in studying Mole- 

 cular Physics.'' The gauge is wedge-shaped. The base of the 

 wedge is formed by taking Angstrom's normal map of the solar 

 spectrum, and extending its scale (the degrees of which are 

 millimetres) both ways, till it reaches zero in one direction and 

 io,coo in the other. The gauge is then completed by erecting 

 a micron or sixthet-metre (sixthet, the fraction represented by 

 one in the sixth place of decimals) over the 10,000 mark and 

 drawing the inclined plane from the top of this to the zero mark 

 at the other end. The gauge is thus a wedge ten metres long, 

 with a gradient of one in 10,000,000, lying upon Angstrom's 

 map ; and the wave-length of any solar ray is the ordinate (the 

 perpendicular distance from the base-line of the gauge up to its 

 sloping top) immediately over the line representing it in the 

 map. The wave-lengths of visible light are the ordinates of 

 this gauge extending from 7 "6 to 3 '8 metres from its apex. At 

 between 3 and 2 metres from the apex we reach an ordinate 

 which is the minimum visibile (the least separation between 

 two points which will admit of their being seen as two with 

 waves so coarse as those of light). The ordinate at one metre 

 from the end is the seventhet- metre (or metre x -000,000, i). 

 The average distance to which the molecules of air dart in 

 the intervals between their encounters is the ordinate at about 

 three-quarters of a metre from the apex {Phil. Mag. for August 

 1868, p. 138). The ordinate of the gauge at i decimetre 

 from its apex is the eighthet- metre (or metre x -000,000,01), 

 The ordinate at one centimetre from the apex is the ninthet- 

 metre (or metre x '000,000,001). This is about the average 

 interval at which the molecules of a gas are spaced, when 

 the gas is at the temperature and pressure of ordinary air 

 \loc. cit., p. 140). The ordinate at one millimetre from the 

 apex is the tenthet-metre (or metre x '000,000,000, 1 ). This is 

 somewhere about the "size" of a gaseous molecule, meaning 

 by this the distance within which the centres of two molecules 

 must come in order that an encounter may take place— that is, 

 that they may be able sensibly to bend each other's path. It 

 may also be taken as about the distance to which the average 

 interval between the centres of the gaseous molecules is reduced 

 when the gas is condensed into a liquid or solid. This is the 

 smallest magnitude for which the gauge is proposed as con- 

 venient. Within the last-mentioned small range numerous and 

 complicated events are known to take place, viz. all those that 

 go on within the molecules, among which are those that 

 originate the lines in the spectra of gases. Whenever any way 

 of estimating these quantitatively shall be discovered, we shall 

 want another and more acute-angled gauge to help us in 

 appreciating them. 



