286 Tension of recently formed Liquid Surfaces. [Mar. 6, 



tension due to oleate requires time for its development. According 

 to the law given above, the ratio of tensions of the newly-formed 

 surfaces for water and oleate (-g 1 ^-) would be merely as 6 : 5.* 



Whether the slight differences still apparent in the case of the 

 stronger solutions are due to the formation of a sensible coating in 

 less than second, cannot be absolutely decided ; but the prob- 

 ability appears to lie in the negative. No distinct differences could be 

 detected between the first and second wave-lengths ; but this obser- 

 vation is, perhaps, not accurate enough to settle the question. It is 

 possible that a coating may be formed on the surface of the glass and 

 metal, and that this is afterwards carried forward. 



As a check upon tie 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, 2 A, (alcohol) = 46*5, 

 h (water) = 30*0, h (alcohol) = 22'0 ; 



but it may be observed that they are not quite comparable with the 

 preceding for various reasons, such as displacements of apparatus and 

 changes of temperature. It is scarcely worth while to attempt an 

 elaborate reduction of these numbers, taking into account the differ- 

 ences 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) 3 = 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 im- 

 portant to make experiments upon this material also. The liquid 

 employed was an infusion of horse chestnuts of specific gravity 1*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 23rd gave 

 the following results : — 



* Curiously enough, I find it already recorded in my note-book of 1879, that A is 

 not influenced by the addition to water of soap sufficient to render impossible the 

 rebound of colliding jets. 



