Oct. lo, 1889] 



NATURE 



i87 



the same in copper conductors, whether it be urged by alternate 

 or by steady currents. 



Prof. G. Forbes, K.R.S., and Mr. W. H. Preece, F.K.S.,in a 

 paper on a new thermometric scale, suggest the joule as the 

 thermal unit instead of the therm or the calorie. 4*2 joules 

 will raise the temperature of i gramme of water at 4° one degree, 

 hence to rai?e i gramme of water from freezing-point to boiling- 

 point requires 420 joules ; and it is suggested that the difference 

 of temperature between freezing- and boiling-points should be 

 represented by 420 units of temperature. 



Mr. J. T. Bottomley, F. R. S., exhibited some large Leydenjars, 

 broken during the testing of a large Wimshurst machine which 

 was being constructed by Sir Archibald Campbell, Bart., of 

 Blythswood. They were excellent examples of multiple fracture. 



Prof. S. P. Thompson, in a paper on sparkless electro-magnets, 

 discussed the various means of suppressing the sparks in the 

 circuits of electro- magnets. The most effective means, he finds, 

 is to surround the core of the magnet with a substantial shield 

 of copper. The author illustrated his method by experiments 

 before the Section. 



Mr. W. W. Haldane Gee and Dr. Arthur Harden read a 

 paper on stereometry. This communication relates to the 

 methods used for the determination of the volumes of bodies to 

 which the hydrostatic method is not applicable. The authors 

 have devised a convenient form of instrument, first proposed by 

 Say, and afterwaids modified by Le-lie, Kopp, Regnault, and 

 Miller. They have also shown that the following method for 

 ascertaining volumes is very generally applicable, and likely to 

 be of considerable service in physico-chemical researches. The 

 body whose volume is desired is inclosed within a vessel of known 

 volume, and then carbon dioxide (or other dry soluble gas) is 

 passed into it for some time. The gas is then displaced by dry 

 air (or other gas), and the volume of the carbon dioxide driven 

 out is ascertained graviiiietrically by absorption in bulbs con- 

 taining caustic potash solution. By first filling the vessel with 

 dry air and then driving it out with carbon dioxide, the volume 

 of the air, and hence that of the body, may also be ascertained 

 volumetncal y, but with less accuracy. The gravimetric method 

 is especially applicable for accurately ascertaining the density of 

 soluble gases. For this purpose it is far more convenient than 

 the process of direct weighing as used by Regnault. 



In a paper on the specific heat of caoutchouc, Mr. W. W. 

 Haldane Gee and Mr. Hubert L. Terry described a number of 

 determinations which had been made of the specific heat of 

 Para india-rubber which had been masticated, hydraulically 

 compressed, and then cut into sheets from 0*22 millimetre to i '40 

 millimetre thick. The rubber was alternated with sheets of tin- 

 foil, and heated for two hours in a steam-jacket at 100° C. A 

 modification of Regnaull's method of mixtures was employed to 

 find the specific heat of the hot rubber. Owing to the non-con- 

 ducting nature of the substance the time of the calorimeter attain- 

 ing its maximum temperature is as long as ten minutes ; hence 

 it has been necessary to apply special formulae for the correction 

 due to cooling. Those proposed by Pfaundler, Pape, and Schuster 

 have been used, and the results calculated in accordance with 

 them. The mean of the best-conducted experiments gives for 

 the Para rubber the number o'486. The investigation is being 

 extended to allied bodies, especially the dififerent forms of 

 vulcanized rubber and gutta-percha. 



Mr. F. T. Trouton read a 1 aper on the temporary thermo- 

 currentsin iron. If a portion of an iron wire connected up to a 

 galvanometer be heated red hot, and the heated portion be 

 caused to travel along the wire by moving the flame, a current 

 is produced, which is due to the fact that when iron changes its 

 molecular state at the teniperature of recalescence this change 

 does not take place ai the same temperature on heating as on 

 cooling, so that when a flame is moved along an iron wire so as 

 to continuously heat it aljove the temperature of recalescence the 

 junction of the altered with the unaltered metal in front is at a 

 higher temperature than of the junction behind the flame. 



Prof. Barrett read a paper on recalescence of iron. 



THE CHEMICAL PAPERS AT THE BRITISH 

 ASSOCIATION. 



/^WING, doubtless, to the numerous chemical industries of 

 ^^ the district, many of the papers read in Section B at 

 Newcastle were of special interest to the technical student. 



The President's Address on "The Melallurgy of Iron" was 

 followed by the Keport of the Ccmirittee for Investigating 

 the Influence of Silicon on the Properties of Sttel. From the 

 results of Mr. Hadfield's experiments, it appears that silicon by 

 itself does rot produce a steel that will harden by water-quench- 

 ing. The briltlencss noticed in ordinary so-called silicon steel 

 is due, not to silicon alone, but to the combined presence of the 

 two hardeners, silicon and carbon. Silicon, up to 6 per cent., 

 dees not destroy the malleability of iron, nor are the magnetic 

 properties greatly affected by increasing percentages of silicon, 

 as is the case with manganese steel. 



The Committee for Establishing an International. Standard 

 for the Analysis of Iron and Steel reported that ihey had made 

 good progress with the woik, and hoped before long to have the 

 necessary analyses completed. 



Seme eurious experiments were described by Mr, J. W. Hogg, 

 on the volatilisation of lead oxide and its action upon glass at 

 low temperatures. If some writing is placed upon a glass plate 

 or platinum-foil, using lead oxide as a pigment, if a polisheci 

 plate of glass be placed over this as closely as possible and pre- 

 vented from actual contact by suitable means, upon now heating 

 up to scarcely visible rednes'-, a distinct reverse of the design 

 will appear upon the upper glass. The quantity of lead oxide 

 which will produce this effect is not shown by the most delicate 

 balance. 



Photographers were interested in Prof. Liveing's account of a 

 new developer, "Eikonogen," which appears to give greater 

 detail than most of those now in use. The tone of the nega- 

 tive is also excellent. Eikonogen is the sodium salt of amido- 

 /3-naphthol-;3-sulphonic acid. 



Mr. C. T. Heycock and Mr. F. H. Neville read a paper or» 

 Raoult's method applied lo alloys. Alloys of a number of 

 metals with sodium and tin were studied. The "atomic fall'' 

 of the freezing-point for aluminium was about half that of most 

 other metals — pointing to twice the present number as the 

 atomic weight of aluminium. Antimony produces a rise in the- 

 freezing-point of the alloy, for some unexplained reason. Con- 

 trary to Raoult's so-callecl second law, it was found that the 

 naluie of the solvent is of influence ; i atomic weight of metal 

 in 100 atomic weights of sodium not giving the same fall as i 

 in ICO of tin. The method would seem to give a means for 

 correcting and verifying atomic weights ; though it does net give 

 much information as to the molecular weight. It was shown 

 that, in accordance with Van 't Hoff's theories on the nature of 

 solution, each metal produces its own lowering of the freezing- 

 point in presence of others. 



On the Friday morning. Prof. Dunstan read the Report on 

 the present methods of teaching chemistry. 



Prof. Bedson afterwards gave an interesting description of Dr. 

 Netto's process, at work on the Tyne, for the manufacture of 

 aluminium fiom cryolite. The cryolite is first fused wiih salt in 

 a reverberatory furnace ; then run out into converters in which 

 sodium is gradually added — about five pounds at a time. Sodium 

 fluoride and metallic aluminium are formed. The sodium is 

 obtained by allowing molten caustic soda to flow gradually onto 

 charcoal contained in a cast-iron retort heated to dull redness. 

 The sodium carbonate formed in the reaction sinks to the bottom 

 of the retoit. The greater concentration of the caustic soda thus 

 produced enables the temperature to be kept lower than in the 

 Castner process. 



An account w as afterwards given, by Mr. J. H. I. Dagger, of 

 the Cowles method for manufacturing aluminium alloys. 



On Monday, numerous Reports of Committees were handed in, 

 the most interesting being that read by Dr, Richardson on the 

 action of light on the hydracids. Dr. Richardson has found 

 that, if while light is allowed to act upon water in presence of 

 oxygen, a considerable quantity of h}drogen percxide is pro- 

 duced. This accounts for the fact mentioned in previous Re- 

 ports, that a mixtuie of dry oxygen with dry hydrogen chloride, 

 or bromide, is unafi'ected by light. 



Dr, Richardson also exhibited and described a new self- 

 registering aclinomeler, based on the fact, discovered by Budde, 

 that chlorine expands in the aclinic rays, contracting again in 

 the dark. 



Prof. 11. B. Dixon gave an account of experiments made by 

 himself and Mr. J. A. Haiker, on the explosion of a mixture of 

 hydrogen, chlorine, and oxygen. It was found, in contradic- 

 tion to previous statements, that steam is produced by the explo- 

 sion even when chlorine is in excess. It was noted that hydrogen 

 and chlorine, when exploded alone, give a sensible contraction. 



