September i, 1892J 



NATURE 



419 



benzol used was measured in the same way ; by sub- 

 tracting this from the contaminating effect of the solution 

 I got the effect of the oil or other substance purposely 

 dissolved. 



Thus with three solutions of Provence oil of equal 

 concentration I got the length of the surface rendered 

 anomalous by the oil contained in four drops : — 



Solution I., 8-3cm. ; Sol. II., 7-8cm. ; Sol. III., 77cm. 



For the sake of verification the other method, viz., 



counting the drops required for making the whole surface 



of the trough anomalous, was also employed. By this 



course the effect of four drops was obtained as follows : — 



Solution I., 8-ocm. ; Sol. II., 7-9cm. ; Sol. III., 77cm. 



The close agreement of the two methods proves that 

 the strip of plate, simply laid across the trough, is suffi- 

 cient to separate normal surfaces. 



Another trial with an ethereal solution of olive-oil gave 

 7'icm., if the somewhat different size of the drops be re- 

 garded ; but I preferred benzine, because its original con- 

 tamination was in most cases only between I'scm. and 

 2-5cm., whilst that of ether amounted to 4 to 6cm. 



The mean of the lengths got by the three solutions was 

 7'9cm., and by this combined with the width of the 

 trough = 5"8cm., we obtain the area of the surface made 

 anomalous by img. of Provence oil : 



7"9. 5- 



= 8460 qcm. 



4.0-001354 



or a density of o"oooii8mg. per qmm. at the beginning of 

 the anomalous state. 



In the following table are collected the results obtained 

 with different substances :— 



The table shows next that the mass required for lower- 

 ing the tension is not the same with different substances, 

 and on the other hand it affords an interesting compari- 

 son between fluid and solid bodies. If the cause of the 

 lowered tension be a film of greasy fluid spread over the 

 surface, the contaminating effect of solid bodies can only 

 be explained by small quantities of such fluids present on 

 the surface or in the interior of the solid. This may be so 

 in many cases, but the effect of stearic acid and sperma- 

 ceti is such as if more than half their weight consisted of 

 oil. The strong effect of colophony, although this did not 

 dissolve entirely in benzine, and the result that tallow acts 

 more strongly than an equal weight of oleine, its fluid 

 component, also appear to me very remarkable. 



After this it seems to me very probable that the con- 

 taminating substances are not spread in coherent films at 

 all, but rather in a state of very fine distribution between 

 the superficial water-molecules, that must be named either 

 emulsion or solution. 



However, only certain organic substances seem to be 

 capable of forming surface-solutions of this kind, whilst 

 the effect of metals and salts, formerly observed by me, 

 was due to incomplete cleanness of the bodies, as later 

 researches have proven. 



Finally I will add some remarks on the thickness of 

 the hypothetical oil-films. The thickness calculated from 

 my observations with olive oil is at the beginning of the 

 anomalous state 1-3 ^/x. In order to derive from this 

 number the thickness at any other condition of the sur- 



i A brown-looking liquid sold under this name in the drug stores. 



NO. I 192, VOL. 46] 



face, it needs only to be multiplied with the relative con- 

 tamination corresponding to that condition, that is, with 

 the ratio of the surfaces. So we get at the smallest rela- 

 tive contamination measurable in my apparatus = 3^5 a 

 thickness of the film = 37.io"2 /x/x. 



For measuring the relative contamination in the ano- 

 malous state, a special mode of procedure was required 

 on account of the imperfect separation of surfaces by the 

 partition. For that purpose I put on the surface that is 

 to be contracted a [-shaped swimming wire, a little shorter 

 than the width of the trough, and by the situation of this 

 mark, following exactly every movement of the surface, I 

 measured the relative length of the latter, instead of 

 reading it from the partition itself. 



The ratio in which the surface must be contracted in 

 order to arrive at the tension at which camphor comes 

 to rest, was very different with various substances, for an 

 instance with stearic acid = f , oleine = J-f , ordinary olive 

 oil = 5, and > with Provence oil the tension in question 

 could not be reached at all, except when the oil was 

 standing on the water in visible drops or films. The cal- 

 culated thickness of the film at the stopping of camphor 

 movements would be with olein = 2' 13/x/it, ordinary olive 

 oil = 6-5/x/i, and with Provence oil still greater, if this 

 liquid were spread equally. A very precise specification 

 of the sort of oil used therefore appears to be necessary, 

 if observations concerning this point are to be compared. 



AGNES POCKELS. 



NOTES. 



The Federated Institution of Mining Engineers will hold its 

 annual general meeting in North Staffordshire on Wednesday, 

 September 7, in the large hall of the First Shropshire and 

 Staffordshire Artillery Volunteers, Shelton. Both on that and 

 on the following day visits will be made to various works and 

 places of interest. 



The Committee appointed to consider whether a national 

 aquarium should be established in Sydney have presented a full 

 and interesting report to Mr. F. B. Sutton, the New South 

 Wales Minister for Public Instruction. They strongly recom- 

 mend that "a commodious building of a substantial and not 

 unsightly character " should be erected, to contain a large series 

 of tanks constituting the public aquarium, with experimental 

 tanks for researches on fish-breeding, &c., in connection with 

 the fisheries of the colony, and laboratories for scientific investi- 

 gation. It is calculated that the " initial cost " would be about 

 ;^"i 0,000, and that an annual amount of about ;^I200 would be 

 needed for salaries and for purchases, rep-^irs, and. other inci- 

 dental expenses. 



In response to an invitation from President G. Stanley Hall, 

 of Clark University, a number of psychologists met from various 

 institutions at that University, Worcester, Massachusetts, on 

 July 8, for the purpose of forming an American Psychological As- 

 sociation. Prof. G. S. FuUerton, of the University of Pennsylvania, 

 presided. After some general discussion on the form of organ- 

 ization the entire matter was referred to a committee. Sessions 

 were held in the afternoon and evening, at which papers were 

 read by Profs. Jastrow, Sanford, and Bryan, and Doctors 

 Nichols, Krohn, and Oilman. It was decided in response to an 

 invitation from Prof. FuUerton to hold the next meeting of the 

 Association in Philadelphia, at the University of Pennsylvania, 

 on Tuesday, December 27. Prof. Jastrow was appointed sec- 

 retary to provide a programme for that meeting. He asked the 

 co-operation of all members of the Association for the section 

 of psychology at the Chicago Exhibition, and invited corre- 

 spondence on the subject. 



