April i6, 1908] 



NA TURE 



575 



mineral kaolinite : A. B. Dick. Further observations on 

 the optical characters of kaolinite from Anglesea lead to 

 some alterations in the data given in a previous paper. 

 The refractive 'ndex is about 1-563 for sodium light, and 

 the optic axial angle, 2V, is about 68° instead of 90°. The 

 double refraction is very low. Kaolinite from limestone at 

 Hambl'ton Quarry, Bolton .Abbey, Yorkshire, and from 

 sandstone near Newcastle-on-Tyne were described. — \n 

 attachment to the goniometer for the measurement of 

 complex lamellated crystals : H. L. Bowman. The 

 apparatus, consisting of a small screen pierced by a pin- 

 hole, can be attached to a goniometer, and is capable of 

 adjustment so that minute portions of a crystal face can 

 be successively illuminated. — A new form of quartz-wedge, 

 a modification of the Wright-wedge : J. W. Evans. A 

 quartz-wedge cut parallel to C is placed over a gypsum- 

 plate parallel to a showing red of the first order, and 

 extending beyond the thin end of the wedge, so that the 

 projecting portions can be used as an ordinary gypsum- 

 plate. The region where the wedge overlies the gypsum 

 is graduated at the position of exact compensation, and at 

 each thousand micromillimetres of relative retardation. If, 

 when placed over a mineral in the diagonal position, the 

 black band is moved towards the thin end of the wedge, 

 the direction of insertion is that of the vibrations which 

 traverse the mineral with the smaller velocity ; if towards 

 the thick end, the direction is that corresponding to the 

 greater velocitv. — Calculation of the chance that the double 

 refraction of a crystal section cut at random shall exceed 

 a particular fraction of the maximum : H. Hilton. The 

 problem is soluble completely for a uniaxial, and partially 

 for a biaxial, crystal. 



Physical Society, March 27.— Dr. Charles Chree, F.R.S., 

 president, in the chair. — Notes on the plug permeameter ; 

 Dr. C. \'. Drysdaie. In the instrument a drill is 

 employed to cut a conical hole in a casting or forging, 

 leaving a pin one-tenth inch diameter standing in the 

 middle. .\ wrought-iron plug carrying a bobbin with 

 magnetising and search coils completes the magnetic 

 circuit, forming a miniature permeameter. Investigations 

 'nave been made showing that the amount of the end effect 

 can be compensated by correcting the value of H in the 

 same ratio for all specimens. Curves were given showing 

 the results obtained by the plug permeameter when the 

 instrument had been empirically calibrated. — ^The use of 

 shunts and transformers with alternate current measuring 

 instruiTients : Dr. C. V. Drysdaie. The paper deals 

 mathematically and experimentally with errors in the 

 magnitude and phase of the current. With shunts, the 

 condition for accuracy at all frequencies is that the time 

 constants of the instrument and shunt should be equal. 

 For current transformers the best results are obtained by 

 keeping the magnetising and core-loss currents as small 

 as possible. — Dynamometer wattmeters 1 Dr. C. V. 

 Drysdaie. An investigation of the theory of the watt- 

 meter, including the effects of shunt inductance and 

 capacity, mutual inductance, eddy currents, wave-form 

 and of iron. It is pointed out that the theory of the watt- 

 meter is much obscured by the use of the correction factor. 

 The correction of a wattmeter should be applied as a 

 lifference. and not as a ratio. \ description of single and 

 double forms of standard wattmeter and of deflrctional 

 wattmeters containing iron was given. 



Institution of Mining and Metallurgy. April q.— Mr. 

 Bedford McNeill, vice-president, in the chair. — The elec- 

 trical equipment of gold mines : H. J. S. Heather. .A 

 review of the present application and future possibilities 

 of the application of electric power to mining operations, 

 with practical notes of installations that have been made 

 under the author's supervision. He points out the relative 

 advantages or otherwise of the continuous and alternating 

 current systems for the purposes of gold-mining work. — 

 Addendum to paper on earth temperatures on Witwaters- 

 rand gold fields : Hugh F. Marriott. A matter dealt 

 with in a previous paper by the same author centred round 

 the mean earth temperatures at the surface in the vicinity 

 of the Rand. This addendum records subsequent investi- 

 gations tending to settle the point in dispute in connection 

 with the attempt to establish a rule for the average 

 inripase of temperature with depth. — The carat weight : 



NO. 2007, VOL. 77] 



E. J. Valtentine. A concise account of the origin and 

 present position of the carat weight as used by dealers in 

 gold and precious stones, with records of the steps taken 

 to establish a standard metric carat for universal adoption, 

 — An electromagnet for testing the suitability of an ore 

 for magnetic separation : L. H. L. Huddart. A descrip- 

 tion of a hand apparatus designed by the author for use 

 abroad. It is suitable for the quantitative determination 

 of the separation to be expected in treating a given ore 

 by means of a powerful magnet. — The gold alluvials of 

 the river Drau in Hungary : A. won Gernet. A brief 

 account of the subject of the title, with comparisons of the 

 relative efiicacy for determining values obtained by panning 

 small samples and counting " colours." 



Royal Astronomical Society, April 10. — Mr. H F. 

 N'ewall, F.R.S., president, in the chair. — Description of a 

 24-inch long-focus coelostat reflector : J. H. Reynolds. 

 The instrument has been constriicted for use in spectro- 

 heliographic work, but is also arranged for taking celestial 

 photographs. The focal length is 38 feet, and the diameter 

 of the plane mirror of the coelostat 28 inches. Specimens 

 of photographs taken with the instrument were shown on 

 the screen. — Dr. A. W. Roberts's method of determining 

 the absolute diinensions of an -Algol variable star : Rev. 

 J. Stein. Dr. Roberts had atteinpted to deduce from the 

 light curve of such a variable the dimensions of the orbits 

 of its components, but Mr. Stein showed that it is 

 theoretically impossible to determine the absolute 

 dimensions of the orbit in this manner. — Note on the 

 newly discovered eighth satellite of Jupiter : Astronomer 

 Royal. The moving object near Jupiter, found by Mr. 

 Melotte upon photographs taken at the Royal Observatory, 

 had been again photographed on March 27, 31, and 

 April 3. It had also been photographed by Dr. Max Wolf 

 at Heidelberg and at the Lick Observatory. It now- 

 appeared that the new object is a satellite of Jupiter, much 

 more distant from the planet than the sixth or seventh 

 satellites. — First approximation to the orbit of J. VIII. : 

 A. C. D. Crommelin. The hypothesis of retrograde 

 motion for the new satellite appeared at present most 

 probable ; from the preliminary elements obtained the 

 sidereal period would probably be between three and four 

 vears, and the distance from the planet about three times 

 that of Satellite \TI. — Variable-star work at Rousdon 

 Observatorv : C. Grover. — .\ new " spanner " sextant : 

 Captain Gadsden. The arrangement consisted of an 

 attachment to a sextant to enable observations to be made 

 when the horizon is obscured or hazy. — Note on the con- 

 ditions for the passage of the earth through the plane of 

 Saturn's ring: H. H. Turner. The late Mr. Proctor had 

 given a general account of the manner in which the earth 

 may pass through the plane of the ring, either once or 

 three times at each favourable opportunity. The present 

 paper gives the explanation in a more compact and com- 

 plete form. — Retrogradation of the sun's shadow: M. E. J. 

 Gheury. — Series of photographs of the Milky Way taken 

 with a small lens of 5J inches focal length : Dr. Max 

 Wolf. — Experiment illustrating the gradually increasing red 

 colour of the sun as it approaches .the horizon at sunset : 

 S. L. Fletcher. 



P.^RIS. 



Academy of Sciences. April 6. — M. H. Becquerel in the 

 chair. — An isomer of diphenylcamphomethane and the con- 

 ditions of its formation : A. Haller and E. Bauer. 

 Details are given of the best method of reducing 

 X=C(C,.,H5l„ 



^CO 



in alkaline solution. The substance obtained, diphenyl- 

 camphomethane, is isomeric with the substance obtained 

 by carrying out the reduction in acid solution, and can 

 be obtained from the latter by boiling with alcoholic 

 potash, and in other ways. \'arious attempts have been 

 made to elucidate the constitutions of these two isomers, 

 but hitherto without success. — A new mineral species from 

 the French Congo : .\. Lacroix. The new mineral is a 

 silicate of copper, differing from dioptase in being attacked 

 with diliiculty by acids, and in its composition, 



Sij.O.^CujsHj, or i2SiO,,.i5CuO,5H,0. 



