High Tensions in Moving Liquids. Ill 



to be to a first approximation the correction to be applied in 

 the case of the coil. Now the coefficient of mutual induction 

 of the coil and disk calculated on the assumption that the 

 section of the coil at right angles to the generating lines is a 

 circle of radius c is equal to 1(3613*75. Adding the calcu- 

 lated percentage correction to this value we have finally for 

 the apparatus used by me 



R=« (16613-75 + 1/14) = 16614-89 n. 



The value of the International Ohm in absolute measure 

 previously given by me in the paper to which I have referred 

 was 



•99976 x 10 9 absolute units. 



The value corrected for the coil ellipticitv is 



•99983 x 10 9 absolute units. 



VII. High Tensions in Moving Liquids. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, 

 QOME years ago, after some holiday enjoyment of making 

 O " ducks and drakes " on a calm sea with flat smooth 

 pebbles, it occurred to me as strange that I had never seen 

 any theory given of "ducks and drakes"; but convinced 

 that a phenomenon, so beautiful as these light rebounds of 

 solid from liquid, and so defiant of those rules of propriety so 

 concisely laid down in our treatises on hydrodynamics for 

 liquids aspiring to be perfect, must have been handled by 

 some master of fluid motion, I thought it would be a good 

 exercise to work out a sketch explanation of the phenomenon 

 and see how far it coincided with the authoritative theory 

 when found. But without an exhaustive search I have yet 

 come to the conclusion that there is really no theory of the 

 phenomenon published, for I have not encountered even an 

 allusion to an explanation of these most elegant "ducks and 

 drakes.'" Under these circumstances, and at a time when 

 hydrodynamicians are making vigorous efforts to break away 

 from the academic allurements of the perfect liquid and to do 

 some service (hard service it seems to be) in the cause of the 

 plain liquids of nature with their lamentable imperfection of 

 an inveterate viscosity, it seems to me that there may be some 

 justification for the brief publication of my rough sketch of a 

 theory, because it brings out the possibility of the existence of 

 high tension in liquids in motion, so that in a general theory 



