July 5, 1906] 



NA TURE 



239 



June 7. — " Effocls of Self-induction in an Iron Cylinder." 

 Hv I'rof. Hrnesl Wilson. Communicated bv Sir William 

 H. I'reecp, K.C.B., F.R.S. 



An iron cylinder lo inches (25-4 cm.) in diameter is 

 traversed in the direction of its axis of figure by an electric 

 current, which is allowed to become steady. Under the 

 action of a sufTiciently large potential difference and non- 

 inductive resistance the total current is suddenly reversed 

 and maintained constant, and its propajlation to the centre 

 of the cylinder is investigated by aid of embedded ex- 

 ploring coils. The results show that a current of about 

 500 amperes takes two minutes to become steady over the 

 whole section of the cylinder. The delay is caused by the 

 opposing electromotive forces induced in the mass by the 

 change of the magnetic fluxes produced by the currents 

 interior lo the successive annuli. When the total current is 

 small, the induced E.M.P'.'s at the centre, for example, 

 occur at once, and then die away. With currents of about 

 300 amperes a second maximum is developed after about 

 eighty seconds. For gradually increased total currents the 

 second maximum occurs at shorter intervals of time after 

 reversal, and becomes the most prominent feature of the 

 phenomenon. 



The results obtained can be applied to cylinders of other 

 diameters than the one experimented upon, and an estimate 

 is made of the time taken fully to make use of the whole 

 section of an iron telegraph wire and steel rails as used 

 in alternate-current traction. 



Mineralogical Society, June 12. — Prof. H. A. Miers, 

 F.R..S., president, in the chair. — Sartorite from the 

 Binnenthal : Dr. C. O. Trechmann. This mineral has 

 hitherto been held to crystallise in the orthorhombic system, 

 and full descriptions have appeared from the pens of 

 vom Rath and Baumhauer. Solly, later, assigns it to the 

 monodinic system, without, however, publishing details. 

 Two very perfect crystals, originally attached to each 

 other, were examined and compared with other crystals and 

 with the results of the above-named authors. Both 

 crystals exhibit conspicuous monoclinic habit, and one is 

 a distinct twin. The elements of vom Rath are : a : b : i- = 

 o-53q : I : 0-619. The elements arrived at now are 

 : (I : 6 : c=i 27552 : i : 1-19487 with /3 77° 48', in which 

 II : b : c correspond with c : b : a of vom Rath. The twin 

 .ind composition plane is a = (ioo), and the twinned crystal 

 i'. a juxtaposition twin on this face. Further evidence of 

 the twinned structure is afforded by many narrow, twin 

 lamellee on the above law. Baumhauer records fifly-nine 

 observed forms on this mineral, including thirteen 

 pyramids. On the above two crystals eighty-seven forms 

 were observed, including thirty-five pyramids. There is 

 little agreement in the angles and forms with those of the 

 other five crystals, or with previous observations. In the 

 zone of the prisms (brachydomes of vom Rath), however, 

 there is a close agreement, sufficient to make it very prob- 

 able that all the examined crystals belong to the mineral 

 sartorite. Further research is necessary on the scarce 

 material in order to show whether two or more morpho- 

 tropically related minerals may not be involved here. — 

 The occurrence of axinite in the area south of Bodmin, in 

 Cornwall : G. Barrow. — Cassiterite pseudomorphs from 

 Bolivia : R. Pearce. The frequent occurrence of cinderv 

 and cellular c.i^siterite in Bolivia suggested that the pseudo- 

 morphs might be after a sulphostannale, but this is not 

 borne out by the crystallographic examination made bv 

 Mr. L. J. Spencer. — Notes on skiodroms and isogyres : Dr. 

 J. W. Evans. The author referred to Prof. Becke's paper on 

 the subject, and. showed that the derivation of the forms and 

 movements of isogyres (the loci in convergent polarised light 

 of vibrations extinguished under crossed nicols) from the 

 skiodroms (the curves expressing the directions of such vibra- 

 tions) are simplified when a microscope with revolving 

 nicols is employed, instead of one with a revolving stage. 

 — .\ pseudomorph of quartz after apophyllite : H. Hartley 

 and N. Garrod Thomas. — .'\ heating stage for the Dick 

 microscope : H. Hartley. — Mr. J. P. De Castro exhibited 

 a large crystal of tantalile from \A-estern .Australia, and 

 Mr. R. Pearce specimens of axinite from St. Ives, 

 Cornwall. 



NO. I914, VOL. 74] 



Faraday Society, June 12. — Mr. W. Murray Morrison 

 in the chair. — The electrolytic deposition of zinc, using 

 rotating electrodes : Dr. T. Slater Price and (.. H. B. 

 Judge. ,\n improved form of apparatus for the electro- 

 lytic deposition of metals, using a rotating kathode, is 

 described. The ordinary beaker is replaced by a tap funnel 

 of about 100 c.c. capacity, so that the electrolyte can be 

 run off at the end of the experiment, thus obviating the 

 use of a siphon. — A simple form of rotating kathode for 

 electrochemical analysis : Dr. F. MoUwo Perkin. The 

 kathode consists of a spiral of platinum wire, or, better, 

 iridio-platinum wire. Nickel wire may be substituted for 

 platinum, and the author recommends its employment in 

 place of the more expensive metal. Attention is also 

 directed to the solubility of platinum anodes, with heavy 

 currents 0-0016 grm. being dissolved in a cyanide solution 

 in thirty-five minutes. — The electrolysis of solutions of 

 thiocyanates in pyridine and in acetone : S. Binning and 

 Dr. F. Mollwo Perkin. On oxidation of thiocyanates with 

 chlorine, persulphates, &c., a yellow colouring matter — 

 canarine — is obtained. By electrolysis of aqueous acidified 

 solutions of thiocyanates an apparently similar product, which 

 was originally described in 18K4 by Lurdow, is obtained. 

 The authors consider that this substance is not identical 

 with the canarine obtained by chemical means, because it 

 shows certain reactions not given by the oxidation product. 



Geological Society, June 13. — Sir Archibald Geikie, 

 Sec.R.S., president, in the chair. — Recumbent folds pro- 

 duced as a result of flow : Prof. W. J. Sollas. Prof. 



Lugeon has described a series of recumbent folds so greatly 

 exceeding in horizontal extension their vertical thickness 

 that they are spoken of as sheets ; they lie flat one on the 

 other, and those higher in the series extend farther to the 

 front than those below, a feature referred to as " deferle- 

 nient." The roots of the lower folds are visible in the 

 high .Alps adjacent, but the roots of the higher must be 

 sought in the zone of Mont Blanc and the Brian^onnais. 

 Thus some of the uppermost folds may have surmounted 

 the obstacle presented by Mont Blanc on their way to the 

 front in the pre-Alps. The features presented by recumbent 

 folds are more suggestive of flowing than bending. Experi- 

 ments have been made with pitch-glaciers (poissiers) in 

 which an obstruction was placed. Folds were produced, one 

 of which was like the Morcles fold behind the Diablerets, 

 another like the Pilatus, and yet another like the Sentis, 

 and the fourth compared with the overslide of the Bavarian 

 front ; all four exhibit d^ferleinent. The lower limb of 

 each fold is adjacent to the similar limb of its neighbours ; 

 but, in another experiment, in which two obstacles were 

 used, the results were nearer to those seen in the moun- 

 tains, where the lower limb of a superior fold reposes on 

 the upper limb of the fold immediately beneath it. — The 

 Crag of Iceland — an intercalation in the basalt-formation •. 

 Dr. Helgi Pjetursson. The existence of fossiliferous de- 

 posits on the west coast of Tjornes, N. Iceland, has been 

 known for 160 vears. Morch enumerates si.\ty-one species 

 of Mollusca, and concludes that the temperature must have 

 been much milder than at present. From the shells, it has 

 been considered that the deposit could not be younger than 

 Middle Reg Crag. Dr. Thoroddsen thinks that these Crags 

 are younger than the Old Basalts of Tjornes. The author 

 finds, however, that, about 500 feet above the sea, they 

 are overlain by the Eastern Basalts. Thus there is a fossil- 

 iferous intercalation occupying part of the great gap 

 between the Tertiary and the Pleistocene rocks. The basal 

 layer of the Pleistocene series is fossiliferous, and has 

 yielded twenty-two species of Mollusca, twenty of which 

 represent a highly Arctic fauna. Certain of the larger 

 basalt-dykes are cut off at the base of the Crag. The 

 absence of the Crag-deposits from other localities is ex- 

 plained bv the erosion of the coast-line. 



Paris. 

 Academy of Sciences. lune 18. — M. H. Foincare in the 



chair. — Researches on the direct synthesis of nitric acid 

 and nitrates from their elements at the ordinary tempera- 

 ture : M. Berthelot. Nitrogen and oxygen were caused 

 to combine at the ordinary temperature under the action 

 of the silent discharge, care being taken that no visible 



