March 19, 1896] 



NATURE 



479 



IV. Solutions of alkaline liDematin, even when enormously 

 diluted (I : 30,000 of water), exert a general absorption of the 

 ultra-violet and extreme violet, but present no trace of definite 

 absorption, either in the extreme violet or the adjacent ultra- 

 violet region. 



The compounds of hsematin with acids, e.g. h?ematin 

 hydrochloride, present even in solutions of great dilution 

 (1:25,000 — 1:50,000) an intense absorption band, which 

 encroaches more and more on the ultra-violet as the strength of 

 the solution increases. With a solution containing one part of 

 crystallised h«;niatin hydrochloride in 20,000 parts of glacial 

 acetic acid the band extends between /* and M, the most intense 

 absorption being between h and L. In highly dilute solutions 

 the band which is still intense absorbs both H and K. 



V. Solutions of hivmochromogen (reduced hsematin of Stokes) 

 exhibit an intense absorption band between h and G. The 

 band has the same position as the band of CO-hremoglobin, but 

 is more intense. From the examination of solutions of various 

 strengths, it results that the mean ray absorbed corresponds to 

 X 420-0. 



\T. The absorption of the extreme-violet and ultra-violet by 

 methiemoglobin indicates that this body is the product of a 

 partial decomposition of the molecule of oxy-h?emoglobin. 



VII. The band in the extreme- violet (and ultra-violet), which 

 is characteristic of hitmoglobin, its compounds, and certain of 

 its iron-containing derivatives, in no respect depends upon the 

 iron in the molecule. This conclusion is based (i) on the fact 

 that none of the compounds of iron, organic or inorganic, 

 possess the property of producing a definite absorption in the 

 extreme- violet or the adjacent ultra-violet ; (2) upon the study 

 of hwmatoporphyrin, a body derived from hrematin by the 

 removal of the iron which this body contains. 



Acid solutions of hi\;motoporphyrin of extreme dilution exhibit 

 an absorption band between // and H. If the solution be 

 slightly more concentrated K is absorbed, and with increasing 

 concentration of the solution the absorption of the ultra-violet 

 extends more and more. Alkaline solutions of haematoporphyrin 

 absorb the same spectral region, but the intensity of the 

 absorption is greater. 



\'III. Neither bilirubin, hydrobilirubin, 'nor urobilin present 

 any definite absorption hand in the region of the spectrum, 

 where the absorption band of haemoglobin and its derivatives 

 occurs. 



Physical Society, March 13.— Prof. Carey Foster, Vice- 

 President, in the chair. — Mr. J. H. Reeves read a paper on an 

 addition to the Wheatstone's bridge for the determination of low 

 resistances. The piece of apparatus described can be used for 

 measuring the resistance of metre lengths of wires of low resist- 

 ance, the only additional apparatus required being a sensitive 

 galvanometer, a Post Office form of resistance box, and a metre 

 bridge. It differs from the ordinary Kelvin bridge in that 

 instead of balancing by varying the length of the standard wire 

 between the two contacts, the distance between these contacts is 

 maintained constant, as is also the length of the wire which is 

 being measured, and balance is obtained by altering other 

 resistances in the network. The author has made a number of 

 tests which show that by his arrangement the resistance of metre 

 lengths of copper wires between the limits of No. 22 S.W.G. 

 and a stranded cable of 7 No. i6's can be determined with an 

 accuracy of O'l per cent. — Mr. Reeves also read a note on the 

 exact value of Matthiessen's standard. Prof. A. Gray (com- 

 municated) said that the author had in his arrangement combined 

 the fixed standard employed in Matthiessen and Hocking's 

 modification of the ordinary bridge with the greater celerity of 

 working arising from the smaller number of operations to be 

 performed when the Kelvin bridge is used. Prof. Gray thinks 

 that he, and probably others, used a method similar to that of 

 Mr. Reeves ; but that the paper is of great utility, since it shows 

 how time may be saved and existing apparatus utilised. Prof. 

 Ayrton said that the advantage of the method described lay in 

 the fact that it was independent of the resistances at the contacts. 

 In Carey Foster's method, however, the coils had to be inter- 

 changed, and inaccuracy might be introduced owing to the 

 varying resistance of the mercury contacts. Unless the mercury 

 cups and the copper plates at the bottom were cleaned every day 

 and the contacts re-amalgamated, the resistance of the mercury 

 cups was very variable. With regard to the question of 

 Matthiessen's standard, it is to be remembered that the specific 

 conductivity of copper has been steadily increasing. This 

 increase was particularly noticeable in the copper prepared by 



NO. 1377, VOL. 53] 



the Elmore process, where, during the deposition of the metal, 

 an agate burnisher is kept continually passing over the surface. 

 Fitzpatrick had explained the rise in conductivity of copjier by, 

 supposing that the density of the copjier now supplied was 

 greater than that of the copper used by Matthiessen, and this 

 explanation seemed quite satisfactory. Mr. Reeves's experi- 

 ments, however, have conclusively shown that this is not the 

 true explanation. It was now possible to obtain copp)er in large 

 quantity having a conductivity of 103 on Matthiessen's scale. 

 The Chairman (Prof. Carey Foster) explained how, when using 

 his method, the accuracy of the result depends not on the elim- 

 ination of the small resistances at the mercury cups, but on the 

 constancy of these resistances. Matthiessen and Dr. Russell 

 found that the specific gravity of copper was apt to be low on 

 account of the presence of dissolved oxide, and they were the 

 first to pass hydrogen gas through the molten metal to remove 

 this oxide. Mr. Appleyard gave a simple diagramatic sketch of 

 the author's arrangement, and also pointed out that better results 

 would probably be obtained with a galvanometer of one or two 

 ohms resistance. Mr. Campbell said that it ought to be definitely 

 settled whether Matthiessen's standard was the conductivity per 

 unit volume or per unit mass. Since copper was always bought 

 by weight, he, as a practical man, strongly advocated the 

 adoption of the mass conductivity ; further, in this case tht 

 measurement of the specific gravity would be avoided. 

 Mr. Reeves having replied, a communication by Herr 

 Puluj on kathode rays was read by the Secretary. — 

 Herr Puluj exhibited some Rontgen photographs taken by 

 means of a form of Crookes' tube, which he had described in a 

 memoir published in 1889. With this tube he has succeeded in 

 obtaining impressions with exposures of only two seconds. Herr 

 Puluj considers that the particles of matter torn from the kathode, 

 which convey negative electrostatic charges, by impact on the 

 glass walls, or on screens, equalise their electric charges, and in 

 this process call forth not merely a disturbance of the material 

 molecules, but also of their ether envelopes. Each jxjrtion of 

 the glass or screen bombarded by the kathode stream becom es 

 the starting-point of ether waves, which, according to their 

 oscillation period and oscillation character are either visible rays 

 (phosphorescence) or invisible Rontgen rays. The oscillations 

 of the invisible rays may take place in the longitudinal direction, 

 but no convincing argument has up to now been brought forward 

 to support this view. — The Secretary also read a note on per- 

 meability to Rontgen rays, by Messrs. Ackroyd and Knowles. 

 The authors have exposed a plate on which a number of pieces 

 of metal, oxides, and sulphates were placed to the Rontgen rays 

 in order to see whether the permeability of bodies to these rays 

 depends on the atomic or molecular weight of the body. In 

 each case it was found that the opacity increased with the 

 molecular weight. Mr. Blakesley said that he considered the 

 Rontgen rays to be the propagation of electrostatic strain 

 through space. With reference to the non-refrangibility of these 

 rays, he had observed in one of the photographs, exhibited by 

 Mr. Swinton, a dark line at the edge of the shadow of a wooden 

 pencil, which might have been due to the refraction of the rays 

 by the wood. Mr. Blakesley has, however, found that this line 

 is due to the varnish on the pencil. Some Rontgen photographs 

 of quartz and ebonite rods not only did not exhibit these dark 

 lines, but there was a very slight indication of a bright line just 

 on the edge of the shadow, which would indicate that the 

 refraction of these rays was less in the rods than in the surround- 

 ing medium.— Mr. Edser exhibited some photographs taken 

 with Mr. Jackson's form of tube, in which a concave kathode is 

 employed. Mr. Edser said that the whole of the tube on the 

 kathode side of the anode plate phosphoresced, so that the 

 Rontgen rays seem to partake of the character of diffused light. 

 Prof. Ayrton said Mr. Jackson had found that the kathode 

 rays form a parallel beam and do not first come to a focus and 

 then again spread out. The Chairman said that some observa- 

 tions made by Mr. Porter agreed with those of Mr. Edser. 

 Mr. Blakesley de.scril>ed the tube used by Puluj, in which a mica 

 screen coated with green calcium sulphide is placed between the 

 kathode and the anode. Mr. Gardner said that there seemed to 

 be some confusion, for when a concave kathode is employed, the 

 kathode rays are brought to a focus and then again diverge. The 

 phosphorescence on the inside of the glass had been shown by 

 Lenard to be due to electricity travelling round the inside sur- 

 face of the glass. Mr. Pidgeon asked if any one had tried the 

 effect of mounting the photographic film on a metal plate. The 

 Chairman said that Captain Abney had found that if the film was 



