1 66 



NATURE 



[December i6, 1897 



from the air of cellars, or from comparatively pure ground, 

 forms an excellent cultivating medium for the bacillus of 

 tubercle when kept away from the disinfecting influence of air 

 and light. 



This power of promoting its growth is particularly manifest 

 when the supporting substance is common wall-paper, though it 

 is quite apparent when very pure filter-paper is used. 



It is further proved that, on these substances, the growth of 

 the bacillus may take place at the ordinary temperatures of 

 dwelling-rooms ; and, hence, that there is no safety against the 

 increase of the organism in ordinary living-rooms in which 

 active tuberculous dust is present, and in which the natural dis- 

 infectants of the bacillus, fresh air and light, are not present in 

 sufficient amount to destroy their virulence. 



Physical Society, December lo. — Mr. Shelford Bidwell, 

 President, in the chair. — Mr. Albert Campbell exhibited : ( i) An 

 experiment to illustrate alternate exchange of kinetic energy. 

 Two brass spheres, each about one inch diameter, are suspended 

 from the same point by equal wires. One of them is then thrown 

 so as to describe a circular orbit. The second sphere, starting 

 from rest, gradually takes up motion from the first sphere, and 

 in turn describes a circular orbit. The first now comes to rest, 

 and the reverse process takes place. This alternating action 

 repeats itself until all the energy is lost in the wires. (2) An 

 experiment to illustrate the low heat-conductivity of glass, and 

 the expansion of glass by heat. A long tube is clamped at the 

 lower end, in a vertical position. One side of it is then heated 

 with the flame of a Bunsen burner, and the glass is observed to 

 bend, moving over a fixed mark near the top of the tube. When 

 the flame is withdrawn, the first position is quickly regained. Mr. 

 Campbell then read a paper on " Temperature compensators 

 for standard cells." Some account of the methods adopted by 

 the author has already been published, he now describes the 

 apparatus. The first compensating arrangement (3) can be used 

 for keeping the potential-diflerence between two points of a 

 conducting system constant at all room-temperatures. Or it can 

 be adapted to modify the voltage of a standard cell to some con- 

 venient whole number. This arrangement (3) resembles a 

 Wheatstone's bridge with the galvanometer-branch removed. 

 One pair of opposite arms is of copper, the other pair is of 

 manganin. The bridge-battery is a Leclanche cell ; this supplies 

 the auxiliary voltage, which is utilised at the two galvanometer- 

 ])i)ints of the bridge, and is there applied in series with the 

 standard cell. In an alternative method, suggested by Mr. C. 

 Crawley, only one of the four arms is made of copper. The 

 second compensating arrangemeiit (4) is intended to maintain 

 constant potential between two points, at all room-temperatures. 

 For this purpose, two wires, a and b, are connected in parallel. 

 One of them, a, is all of manganin, the other, b, is partly 

 copper and partly manganin. Constant current is applied 

 at the ends of a and b. The various resistances are chosen 

 so as to give constant difference of potential between 

 the ends of the manganin portion of b. By this method the 

 potential-difference can be maintained to within i in 2000. Mr. 

 Swinburne said that twelve or thirteen years ago he had given a 

 good deal of thought to compensation by wires of different 

 temperature-coefficients. The first thing he tried was a Wheat- 

 stone's bridge. This was compensated by making the bridge- 

 arms of wires whose temperature-coefficients differed — as, for 

 instance, platinoid and copper. He then applied the same 

 principle to the compensation of standard cells, using a poten- 

 tiometer method that gave direct readings, and to the com- 

 pensation of voltmeters and watt-meters. These results were 

 published between 1885 and 1890, in the electrical journals. 

 He believed that Mr. Evershed had also developed this idea, by 

 putting "back" turns on voltmeters, and by other differential 

 devices. The details of Mr. Campbell's apparatus had a few 

 points of special interest. The way in which he connected up 

 the bridge (3) seemed particularly worthy of notice. Prof. 

 Ayrton asked whether thermo-electric effects produced difficulty 

 in the compounded arrangement. Mr. Campbell said the 

 system was symmetrical, and the thermal currents were con- 

 sequently neutralised. Mr. Appleyard, referring to experiment 

 (2), said it was identical with one that had been shown for the 

 past eight years at lectures at Cooper's Hill College. It was 

 specially of interest as illustrating the deflection that occurs 

 with girders and bridges when exposed on one side to sunshine. 

 — Mr. J. Rose-Innes read a mathematical paper on Lord Kelvin's 

 absolute method of graduating a thermometer. Lord Kelvin 

 has investigated the cooling effects exhibited by various gases 



NO. 1468, VOL. 57] 



in passing through a porous plug. He found that for any gas, 

 kept at the same initial temperature, the cooling effects were 

 proportional to the difference of pressure on the two sides of 

 the plug. He also found that, for any one gas, the cooling 

 effect per unit difference of pressure varies approximately as 

 the inverse square of the absolute temperature. This rule 

 holds very well in the case of air ; it is not so satisfactory for 

 carbonic acid ; it fails for hydrogen. With hydrogen there is 

 a heating effect that increases, if anything, when the temperature 

 rises. Mr. Rose-Innes proposes an empirical formula, contain- 

 ing two disposable constants, o and /3, characteristic of the gas 

 in question. Denoting by T the absolute temperature, he finds 

 that, very approximately, the cooling effect is given by the ex- 

 pression (a/T - j8) This relation includes the three cases — air, 

 hydrogen, carbonic acid — under one form, and thus enables 

 them to be treated in one common investigation. Moreover, 

 the differential equation concerned in the thermo-dynamic scale 

 is thereby rendered more manageable ; it leads to simpler 

 algebraic results after integration. The paper discusses the 

 thermo-dynamic correction for a constant-pressure gas-ther- 

 mometer, and the correction for a constant-volume gas-ther- 

 mometer ; also an estimate of the absolute value of the freezing- 

 point of water ; the results obtained take, for the most part, a 

 very simple shape, using the above expression for the cooling. 

 Dr. S. P. Thompson said the empirical expression, (o/T-8), 

 indicated that at some particular temperature the cooling effect 

 vanished ; that was a point suggestive of useful results if in- 

 vestigated by experiment. Mr. J. Walker read a communica- 

 tion from Mr. Baynes on the paper, and remarked upon the 

 desirability of adopting two constants. He thought that further 

 experiments should be made to discover how specific heat at 

 constant temperature depends on temperature. The calculated 

 values for hydrogen were too few to be taken as evidence of the 

 validity of the rule. Mr. Rose-Innes, in reply, said that from 

 what was known of hydrogen, it might be expected to behave 

 at ordinary temperatures as air behaves at higher temperatures. 

 His object was, if possible, to include in one formula the case 

 of the three investigated gases. This was better than having a 

 separate formula for each gas. Whether or not hydrogen was 

 confirmatory with air and carbonic acid, might be considered as 

 sub judice ; it required further experimental data to test the 

 formula in that case. — The President proposed a vote of thanks 

 to the authors, and the meeting was adjourned until January 21, 

 1898. 



Chemical Society, November 18. — Prof. Dewar, President, 

 in the chair. — The following papers were read :— On the de- 

 composition of camphoric acid by fusion with potash or soda, 

 by A. W. Crossley and W. H. Perkin, jun. Camphoric acid, 

 when fused with alkali, gives a mixture of a number of fatty 

 acids with dihydrocamphoric acid, CioHig04, pseudocamphoric 

 acid, CioHig04, and an acid of the composition C9Hig04 ; the 

 results are explained and constitutions assigned on the assump- 

 tion that camphoric acid has the constitution, 



CH2.CH (COOH). 

 I >CH2. 



C Me2.CMe(COOH)'^ 



— Experiments on the synthesis of camphoric acid, by W. H. 

 Bentley and W. H. Perkin, jun. The authors have prepared 

 isobutylmethylhydroxyglutaric acid, CHMe2.CH„.CH(COOH). 

 CH2.CMe(COOH)OH, hoping that by loss of water it would 

 give an acid of the constitution assigned in the previous paper to 

 camphoric acid ; by loss of water, however, a lactonic acid or 

 its derivatives were usually obtained. — Synthesis of an isomeride 

 of camphoronic acid, by S. B. Schryver. — The action of 

 magnesium on cupric sulphate solution, by F. Clowes and R. M. 

 Caven. When magnesium acts on copper sulphate solution, 

 hydrogen, cuprous oxide, and copper are produced. — Properties 

 and relationships of dihydroxytartaric acid, by H. J. H. Fenton. 

 Dihydroxytartaric acid is readily prepared by oxidising dihy- 

 droxymaleic acid in aqueous solution ; it gives a quantitative 

 yield of tartronic acid on heating. — The molecular association of 

 liquids and its influence on the osmotic pressure, by H. Cromp- 

 ton. The author shows that Planck and van Laar's demonstra- 

 tions that association can have no effect on osmotic pressure are 

 invalid owing to faulty reasoning. 



Geological Society, December i. — Dr. Henry Hicks, 

 F.R.S., President, in the chair. — A revindication of the 

 Llanberis unconformity, by the Rev. J. F. Blake. In a paper 

 published in the Quarterly Journal oi the Society for 1893, ^^^ 



