404 



NA TV RE 



[September .^o, 1909 



Fascicl-les I and 2 of the Bulletin des Seances de 

 la Society franfais de Physique for 1909 contain thirteen 

 memoirs, several of which have already been noticed in 

 these columns. Amongst those not previously dealt with 

 may be mentioned that by M. G. Delvalez, on the Hall 

 effect in liquids. According to the electronic theory of 

 conduction of electricity, this effect should be extremely 

 small, while experiment appeared to show that it was a 

 million times greater than the theoretical value. M. 

 Delvalez has succeeded in showing that these observed 

 effects were due to the convection currents in the liquid, 

 set up because it is a mobile conductor carrying current 

 through a magnetic field. The motion generates an electro- 

 motive force, which has been measured as the Hall effect. 

 By using an alternating electromotive force to produce his 

 main current, and arranging to balance the Hall electro- 

 motive force against the fall of potential down an induc- 

 tion free resistance traversed by the main current, he 

 has shown that the effect is very small, certainly less than 

 one three-thousandth of the value previously observed. 



The use of platinum felt, as suggested by Monroe in 

 1888, in place of asbestos as a filtering medium is recom- 

 mended by Mr. W. O. Snelling in a paper in the Journal 

 of the .American Chemical Society (vol. xxxi., pp. 456-461). 

 In addition to its insolubility in almost all the ordinary 

 chemical agents, it has the advantage of extraordinary 

 porosity, combined with the power of retaining completely 

 and easily such finely divided precipitates as barium 

 sulphate and calcium oxalate ; a series of tests showed that 

 the filtration was six times more rapid than with an asbestos 

 filter containing one-third the quantity of asbestos. The 

 precipitate can be dissolved off, and the felt used again 

 and again ; moreover, a damaged filter can readily be 

 patched by the adding of chloroplatinic acid and igniting. 

 The use of the " Monroe crucible " for atomic-weight deter- 

 minations is especially advocated. .Another issue of the 

 same journal contains a paper by Mr. J. T. Stoddard on 

 rapid electro-analysis with stationary electrodes (ibid., 

 pp. 385-390), in which it is claimed that by using a kathode 

 of gauze or of mercury, a stationary anode, and a heavy 

 current, complete decomposition of the metal can be 

 effected as rapidly as with a rotating electrode; under 

 these conditions the liberation of gas, and the convection 

 currents consequent on the heating of the liquid, appear 

 to provide sufficiently for the agitation of the fluid without 

 recourse to mechanical methods. 



The Philippine Journal of Science for March contains a 

 third paper by Raymond F. Bacon on the Philippine 

 terpenes and essential oils, and a paper by Mr. H. D. 

 Gibbs on the oxidation of phenol. The latter author has 

 taken advantage of the tropical sunshine to study the red 

 coloration which is developed by phenol when exposed to 

 air and light, and has carried out the investigation with 

 remarkable care and thoroughness. He shows that the 

 phenol becomes coloured in presence of oxygen, but not 

 of hydrogen, nitrogen, and carbon dioxide. The action is 

 caused by oxidation, quinol, quinone, catechol, and carbon 

 dioxide being produced ; the principal coloured compounds 

 are probably quinone condensation products, the red colour 

 being attributed to phenoquinone. The oxidation is not 

 appreciable in the dark at room-temperatures, but becomes 

 measurable at 100°, and fairly rapid at the boiling point 

 of phenol. In sunlight the rate of coloration is rapid, and 

 increases with the temperature ; it is affected by the ultra- 

 violet absorption of the glass, by atmospheric conditions, 

 and by the altitude of the sun. Ozone is very reactive ; 

 it gives the same products as oxygen, and in addition 

 XO. 2083, VOL. Si] 



glyoxylic acid has been detected. Anisol, the methyl ether 

 of phenol, gives no coloration either by the action of ozone 

 or of oxygen and sunlight. 



Messrs. E. B. .Atkinson .wd Co., of Hull, forward us 

 an improved pattern of Soxhlet's apparatus for the extrac- 

 tion of oils and fats. The new form is fitted with a glass 

 stop-cock on the syphon tube. By regulating the over- 

 flow, the thimble can be kept full of the solvent during 

 the extraction, instead of being alternately filled and 

 emptied. Also, by closing the stop-cock at the end of an 

 operation, the solvent can be retained in the upper part 

 of the apparatus ; this allows the flask containing the ex- 

 tracted fat to be almost freed from the solvent, so that 

 it can be placed straightway in the drying-oven. A bulb 

 on the upper part of the side-tube facilitates the passagq 

 of the vaporised solvent if liquid should collect there. The 

 new pattern thus appears to have distinct advantages over 

 the older form. 



The use of the Walschaerts valve gear on American 

 locomotives has been greatly extended since its introduc- 

 tion into the States a few years ago. The advantages of 

 this gear render it very suitable for the large engines 

 employed in America, and its success has led to experi- 

 ments with others of a similar type. Several railways are 

 now trying the Pilliod motion, a gear made by the Pilliod 

 Company of Chicago, and described in the Engineer for 

 September 3. In this gear, as in the Walschaerts, the 

 motion is derived partly from a return crank on the 

 main crank-pin and partly from the crosshead. The 

 moving parts are the same for any class of engine, and 

 weigh about 1000 lb. There is no load on the reversing 

 lever, which can be unlatched and moved in any condition 

 with the regulator either open or closed. The motion is 

 expected to effect a considerable saving in fuel and in 

 maintenance and repairs. The release is late ; thus with 

 cut-off at 25 per cent, the release is at 85 per cent. ; the 

 Walschaerts gear, with a similar cut-off, releases at about 

 65 per cent, of the stroke. Special adaptability for high 

 speeds is claimed. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences in Octoher : — 

 Oct. 6. Ilh. 59m. to I2h. 34m. Moon occulls k Geniinorum 

 (mae. 37I. 

 8. loh. 37m. Minimum of .Algol (/3 Persei). 



1 1. 7h. 26m. ., ,, 



12. 23h. Venus in conjunclion with 5 Scorpii (s'ar 



o°7' S.). 



13. 6h. Saturn in opposition to the Sun. 



17. I7h. Venus in conjunction with the Moon (Venus 

 2°I7'S.). 

 18-24. Epoch of October meteoric shower (Orionids, Radiant 

 92°+ 15°). 

 20. Saturn. Major axis of outer ring =46'I5", Minor axis 



= 9'2i". 

 27. Sh. Saturn in conjunclion with the Moon (Saturn 



i°i7'N.), 

 ,, igh. Mercury at greatest elongation west. 

 31. gh. Sm. Minimum of Algol (/3 Persei). 

 Observations of Hallev's Comet, 1909c. — Photographs 

 showing Halley's comet were obtained at the Greenwich 

 Observatory, with the 30-inch reflector, on September 9, 

 two days before it was discovered by Prof. Wolf. Owing 

 to the proximity of the moon the two exposures were 

 limited to thirty minutes and twenty-five minutes re- 

 spectively, and the very faint cometary images were not 

 identified until after the receipt of the telegram announcing 

 the discovery at Heidelberg. The positions determined gave 

 corrections of -(-24s. and —4' to the ephemeris published 

 in No. 4330 of the .Astronomische Nachrichten. 



In a supplement to No. 4356 of the Astronomische 

 Nachrichten, where the above observations are recorded, 



