568 



NATURE 



\April 17, 1890 



As a check upon the method, I thought it desirable to 

 apply it to the comparison of pure water and dilute 

 alcohol, choosing for the latter a mixture of 10 parts by 

 volume of strong (not methylated) alcohol with 90 parts 

 water. The results were as follows : — 



2\ (water) = 38-5, 

 h (water) = 30:0, 



2\ (alcohol) = 46-5, 

 h (alcohol) = 22 'o ; 



but it may be observed that they are not quite comparable 

 with the preceding for various reasons, such as displace- 

 ments of apparatus and changes of temperature. It is 

 scarcely worth while to attempt an elaborate reduction of 

 these numbers, taking into account the differences of 

 specific gravity in the two cases ; for, as was shown in the 

 former paper, the observed values of X are complicated 

 by the departure of the vibrations from isochronism, 

 when, as in the present experiments, the deviation from 

 the circular section is moderately great. We have — 



(46 •5/38-5)2 = 1-46, 



30/22 = 1-36; 



and these numbers prove, at any rate, that the method of 

 wave-lengths is fully competent to show a change in 

 tension, provided that the change really occurs at the 

 first moment of the formation of the free surface. 



In view of the great extensibility of saponine films it 

 seemed important to make experiments upon this material 

 also. The liquid employed was an infusion of horse 

 chestnuts of specific gravity i '02, and, doubtless, contained 

 other ingredients as well as saponine. It was capable 

 of giving large bubbles, even when considerably diluted 

 (6 times) with water. Photographs taken on November 

 23 gave the following results : — 



2\ (water) = 39*2, 

 h (water) = 30-5, 



2\ (saponine) 

 h (saponine) 



39'5. 

 207. 



Thus, although the capillary heights differ considerably, 

 the tensions at the first moment are almost equal. In 

 this case then, as in that of soap, there is strong evidence 

 that the lowered tension is the result of the formation of 

 a pellicle. 



Though not immediately connected with the principal 

 subject of this communication, it may be well here to 

 record that I find saponine to have no effect inimical to 

 the rebound after mutual collision of jets containing it. 

 The same may be said of gelatine, whose solutions froth 

 strongly. On the other hand, a very little soap or oleate 

 usually renders such rebound impossible, but this effect 

 appears to depend upon undissolved greasy matter. At 

 least the drops from a nearly vertical fountain of clear 

 solution of soap were found not to scatter (Roy. Soc. Proc, 

 June 15, 1882). The rebound oi jets is, however, a far 

 more delicate test than that of drops. A fountain of 

 strong saponine differs in appearance from one of water ; 

 but this effect is due rather to the superficial viscosity, 

 which retards, or altogether prevents, the resolution into 

 drops. 



The failure of rebound when jets or drops containing 

 milk or undissolved soap came into collision has rot been 

 fully explained ; but it is probably connected with the 

 disturbance which must arise when a particle of grease 

 from the interior reaches the surface of one of the liquid 

 masses. 



P.S. — I have lately found that the high tension of 

 recently formed surfaces of soapy water was deduced by 

 A. Dupr^ (" Thdorie Mecanique de la Chaleur," Paris, 

 i869),aslongagoas i869,from some experiments upon the 

 vertical rise of fine jets. Although this method is less 

 direct than that of the present paper, M. Dupre must be 

 considered, I think, to have made out his case. It is 

 remarkable that so interesting an observation should not 

 have attracted more attention. 



NOTES. 



It is stated that the committee to be appointed to inquire into 

 colour-blindness in seamen, railway guards, and others, will not 

 be exclusively confined to members of the Royal Society. Some 

 gentlemen who, like Dr. Farquharson, M.P., and Mr. Bickerton, 

 of Liverpool, have taken special interest in the question will, it 

 is said, be asked to join the committee. A further question on 

 the subject will, in the course of a few days, be put to the 

 President of the Board of Trade. 



We regret to have to record the death of Sir John Henry 

 Lefroy, F. R. S. lie died on Friday evening last at his residence, 

 Lewame, a few miles from Liskeard. He was seventy-three 

 years of age. He entered the Royal Artillery in 1834, and was 

 Director of the Magnetical and Meteorological Observatory at 

 St. Helena from 1840 to 1841, whence he moved to a similar 

 position at Toronto in 1842. During the next year he made a 

 magnetic survey of the interior of North America from Montreal 

 to the Arctic Circle. From 1854 to 1855 he was scientific 

 adviser to the Duke of Newcastle at the War Office on subjects of 

 artillery and inventions, and in 1855 he was sent, as lieutenant- 

 colonel, on a special mission to the seat of war. Afterwards he 

 held several high military appointments. In 1882 he was made 

 a general, and retired. He had been elected a Fellow of the 

 Royal Society in 1848. 



Mr. Thomas Johnson, Demonstrator in Botany at the 

 Normal School of Science and Royal School of Mines, has 

 been appointed to succeed the late Prof. McNab, as Professor of 

 Botany at the Royal College of Science, Dublin, Prof. Johnson 

 begins lecturing this term. 



An International Medical Congress was opened at Vienna on 

 Tuesday, and will continue its sittings until to-morrow (Friday). 

 Many physicians from the principal Europe an countries are taking 

 part in the proceedings. 



At the next meeting of the Anthropological Institute, on 

 Tuesday, April 22, M. Jacques Bertillon will give a lecture, 

 with demonstrations, on the method now practised in France 

 of identifying criminals by comparing their measures with those 

 of convicted persons in the prison registers. The registers con- 

 tain the measures of many tens of thousands of persons, with 

 their photographs ; yet M. Bertillon's method enables the 

 reference to be rapidly effected. It is thought, therefore, that 

 the authorities in England who are concerned with the police, or 

 with the identification of deserters from the army or the navy, 

 may be glad of the opportunity of hearing M. Bertillon's 

 exposition. 



The Meteorological Office has adopted a new way of spread- 

 ing information as to the condition of the weather on our coasts. 

 On Monday it began to exhibit, at 63 Victoria Street, West- 

 minster, outside the building, a series of boards, showing the 

 state of the wind, weather, and sea at Yarmouth, Dover, the 

 Needles, Scilly, Valentia (Ireland), and Holyhead. The in- 

 formation given is for 8 o'clock in the morning and 2 o'clock in 

 the afternoon, and the notice, are posted up at about 9.30 a.m. 

 and 3 p.m. respectively. The words are printed in clear type, 

 and can be read by those having ordinarily good sight from the 

 pavement or roadway. 



At the meeting of the Institution of Civil Engineers on 

 Tuesday evening, Sir Frederick Bramwell read a paper on 

 the application of electricity to welding, stamping, and other 

 cognate purposes. 



There has been some talk lately about a scheme for the con- 

 struction of a bridge across the Bosphorus. The Turkish news- 

 paper Hakikat gives some particulars of the project a propos of 



