60 Spontaneous Segmentation of a Liquid Annulus. [Dec. 18, 



be necessary to evaluate the average centripetal velocities during 

 the fall of the portions of the annulus at the positions of maximum, 

 mean, and minimum thickness, for a given distribution of the liquid, 

 which can only be done when the connexion between time of segmen- 

 tation and thickness is known. 



The very fact of segmentation taking place sooner in one portion of 

 the annulus than another is itself a source of asymmetry, as was 

 shown by the experiment of liberating a portion of an annulus, which 

 was found to contract in length and straighten itself with great 

 rapidity. 



Thus after a fall of 12 centims., a portion of annulus No. 1, repre- 

 sented in fig. 3, gave on the sand the impression represented in fig. 4. 



The sharp curvature of the free ends is of course the cause of the 

 shortening. Its influence was often noticed in the case of elliptical 

 marks, inasmuch as the extremities of the row of ill-divided impres- 

 sions were separated from the extremities of the well-divided portion 

 by spaces rather greater than the average distance between neigh- 

 bouring drops elsewhere. 



It is evident that the method of liberation adopted in these experi- 

 ments is not applicable to a straight cylinder, which will immediately 

 begin to contract and shorten under the influence of the pressure of 

 the curved ends, unless it be prevented from doing so by being kept 

 stretched between metallic terminals to which it adheres ; such termi- 

 nals would, unless of relatively great mass, require to be fixed to a 

 frame which of course must fall with the cylinder. The impurity 

 introduced by using an amalgamated metal would be a source of error, 

 as M. Plateau has pointed out in his own experiments, which how- 

 ever, might be avoided by adopting the plan mentioned by Professor 

 Guthrie, " Proc. Roy. Soc," vol. xiii, p. 458, of using platinum, to 

 which, when once rubbed with an amalgam of sodium, mercury will 

 ndhere closely and without amalgamation. 



The experiment would, in this manner, be probably quite feasible. 



I have endeavoured by smoking the wooden disk, to render it un- 

 wetable by water, and so to liberate an annulus of that liquid, but so 

 far without success ; the water always finds its way here and there 

 through the coating of lamp-black and adheres to the disk. 



