October 26, 1905J 



NA TURE 



6^.1 



finds the position of tliese bands to be consistently nearer 

 to the red end of the spectrum. The dilTcrence in the 

 position of the bands in the spectrum of benzene vapour 

 and of benzene in solution only proves, of course, the 

 applicability of Kundt's rule. We are also pleased that 

 Prof. Hartley has been able to see the second band on our 

 list (^. = 2656), which, coupled with the fact that Friederichs 

 has also measured it, we feel is a most important confirm- 

 ation of our observations. 



As regards the eighth band (A. = 2330) which has been 

 measured in the absorption spectrum of benzene vapour by 

 Friederichs (whose work we were, of course, unaware of 

 when we wrote our paper), we have made a most careful 

 search for it. We have re-e.Kamined our original plates 

 and have taken several more photographs, but have been 

 unable to find any trace of it. We must therefore conclude 

 that it is absent from the spectrum of benzene in alcoholic 

 solution. 



There is one other point in Prof. Hartley's letter; he 

 says we have overlooked some points of importance in his 

 paper with Prof. Dobbie when we state that they only 

 found six bands. It is quite true that in their paper 

 Hartley and Dobbie refer in their table of measurements 

 to another band of very short persistence which they mark 

 as doubtful at 5 mm. thickness of N/io solution, and very 

 doubtful at 4 mm. thickness. In the letterpress, however, 

 they speak of only ^ix bands, and in all later publications 

 benzene is stated to show six absorption bands. In the 

 British Association report, and even in Prof. Hartley's 

 paper to the Chemical Society on May 17 of this year, he 

 speaks of si.x bands (Chem. Soc. Proc, xxi., 167). We 

 therefore assumed that Prof. Hartley, on further consider- 

 ation, had concluded that this doubtful band was not a 

 true benzene absorption band. As we ourselves had seen 

 no trace of this band, we in our paper before the Chemical 

 .Society (Trans. Chem. Soc, Ixxxvii., 1332) stated that 

 Hartley and Dobbie had found only si.x bands. 



Prof. Hartley's ideas and work upon the absorption 

 spectra of organic compounds in the ultra-violet are of the 

 greatest importance ; he was the first to show how the 

 constitution of certain compounds could be established by 

 this means. Prof. Hartley's method of " testing " a 

 molecule by means of its absorption spectrum, we are 

 sure, will prove of the greatest possible value in the hands 

 of chemists. E. C. C. B.4LY. 



J. Norman Collie. 



University College, October 12. 



Action of Radium Salts on Gelatin. 



H.^viNG occasion to give a demonstration of the proper- 

 ties of radium some little time ago, I determined to attempt 

 the preparation of some of the organisms as described by 

 Mr. J. Butler Burke. 



The method employed was to sprinkle a few specks of 

 the radium salt upon the surface of some sterilised gelatin 

 contained in a test-tube, and then to await development. 

 That did not take long. Almost at once a faint cloudiness 

 appeared to start under the speck of salt which extended 

 downwards into the gelatin, in some cases after twenty- 

 four hours reaching the depth of one centimetre. No heat- 

 ing was required to bring about this "growth," which 

 resembled to the unaided eye an ordinary mould. The 

 experiment was made with radium preparation of varying 

 degrees of activity, but it was soon observed that the 

 degree of activity in the salt had little influence on the 

 growth, a salt of radium barium bromide containing 

 I / 1000 of its weight of active salt being nearly as 

 efficacious as one containing i/ioo. (The more pure speci- 

 mens which I possess were too precious to experiment 

 with.) 



As the specimens used were composed chiefly of barium 

 salt, it occurred to me that it might be interesting to try 

 the effect of the pure barium salts on the gelatin. This 

 was done, with the surprising result that the " growths " 

 were just as easily obtained as with the radium prepar- 

 ation — or even more so. I have tested all the barium salts 

 at my disposal, and find the following produce the effect : — 

 Barium, oxide, dio.xide, chloride, bromide, iodide, nitrate, 

 arilate, tartrate, and sulphovinate, while the phosphate, 



NO. 1878, VOL. 72] 



carbonate, sulphate, and borate do not act. Thus the 

 soluble salts are active, and the insoluble ones inactive. 



The method adopted for the experiments was as 

 follows : — Some clear gelatin was poured on to a glass 

 slip and allowed to set. .A tiny speck of the salt was placed 

 on the gelatin and covered with a thin glass. This slip 

 was then placed on the stage of a microscope and ex- 

 amined with a 5-inch power. At once the " growth " was 

 seen to shoot out from the speck, and it appeared to 

 consist of bubbles, some large, but most of them very 

 small. Half an hour afterwards the speck had dissolved, 

 leaving in its place a nebulous patch many times the size 

 of the speck. The action of barium iodide is particularly 

 rapid, while that of the hydrate is rather slow. I have 

 tried uranium and thorium salts, both of which affect the 

 gelatin rapidly, but do not produce the " growths." The 

 action of these salts upon gelatin seems to point out an 

 interesting field of inquiry, which I propose to follow. 



W. A. DoCGL.iS RUDGE. 



Woodbridge School, .Suffolk. 



The Problem of " Shadow-bands." 



Subsequently to the Algiers eclipse of 1900, it occurred 

 to me that the " shadow-bands " visible at times of total 

 solar eclipse might be merely another aspect of the " boil- 

 ing " distortions of the sun's limb inseparable from daily 

 observations. The last few years have therefore been 

 employed by me in studying the characteristics of " boil- 

 ing " with the view of making a direct comparison of 

 evidences at the first opportunity. This opportunity 

 presented itself in the recent total solar eclipse observed 

 by me at Cds Catald, in Mallorca, on August 30 last. 



Employing " Carrington's method " of projecting the 

 sun's image with a small telescope, the first observation 

 made at about 10 a.m. recorded the existence of two dis- 

 tinct layers of cloud, the lower one travelling N.E. by 

 S.W., and the upper one W.S.W. by E.S.E., giving con- 

 fused and erratic " boiling." Further observations revealed 

 an increased prevalence of the N.E. cloud system, but the 

 drift from W.S.W. was still in evidence. At 11.35, how- 

 ever, it transpired that the W.S.W. system alone pre- 

 vailed, and all trace of the drift from N.E. had abated. 

 Continuing the observation without any relaxation through- 

 out the phase of partial eclipse until within a few minutes 

 of totality, I was able to ascertain that the " boiling " 

 movements along the advancing limb of the moon were 

 throughout absolutely in agreement in every particular 

 with the movements of distortion affecting the still un- 

 covered limb of the sun. Observations by projection were 

 abandoned at ih. i8-om. for the purpose of securing a 

 naked-eye view of "shadow-bands." A very successful 

 view of these was secured. Their direction of flight deter- 

 mined on the spot, and afterwards corrected by Dr. Hunter, 

 of Edinburgh, by the compass, proved to be W.S.W. by 

 E..S.E. It is noteworthy that at Palma, where the eclipse 

 conditions were marred throughout bv the cloud bank that 

 had threatened to overwhelm us at Cds Catald (only four 

 miles S.W. of Palma), the " shadow-bands " were observed 

 to take a direction N. 30° E. by S. 45° W. 



C.iTiiARiNE O. Stevens. 



Bradfield, Berks, October 20. 



Rhymes on the Value of tt. 



Now I know a spell unfailing, 



3 I 4 I .S 9 



.An artful charm, for tasks availing, 

 2 fi 5 .1 5 8 



Intricate results entailing. — 



9 7 9 



Not in too exacting mood, 



3238 4 



(Poetry is pretty good), 



626 4 



Try the talisman. — Let be 



.V 3 . 8 . 32 



Adverse ingenuity ! 



7 9 



