certain Dilate Aqueous Solutions. 



381 



The results obtained by this method were very erratic. 

 The wave-lengths found on any one day would agree fairly 

 well among themselves, but those obtained on different days 

 seldom agreed at all. Later on it was found that the appa- 

 rent wave-length depended upon how many waves were 

 included between the settings. 



After trying every plan I could devise to find the trouble, 

 I at last decided to measure each individual wave and see if 

 these separate determinations would throw any light on the 

 difficulty. In this series of measurements I went as close to 

 the fork as I could measure, and I found (although these 

 separate determinations were very rough) that the apparent 

 wave-length increased as the fork was approached. As a last 

 resort I attributed this effect to the rise of the liquid against 

 the plate which generates the ripples, although I did not 

 think that this could affect waves two centimetres distant. 

 To test this experimentally, the plate that was well wetted 



Fig. 2. 



Fig-. :j. 



Distance from fork. 





1-0 



BBBfl IBBBH 





| - |. • 1 • ' 1 „ | ' 1 ; n 





0-9 



. 1 - 1 1 1" 1 1 ' 1 





0-8 



HBBBBHBHBBBfl 





p'la|"E idior IWETTED 

 BY THE LIQUID 





0-7 

 0-6 





S95EEE3EES99 



SJ3 



BBBBUBBBBflfl 



<D 



0"5 



BBBNB 



Oj 





Hll 





0-4 

 0-3 











BBflflBBBflBflflfl 





0-2 



l ; i i | ; 





o-i 



~h j — ty-f-— 7 





0-0 



" ; 



12 3 4 5 



Distance from fork. 



was replaced by one coated with paraffin. It was now found 

 that the waves apparently decreased as we approach the fork. 

 This proved that, contrary to expectations, the effect of the 

 meniscus makes itself felt two or three centimetres from the 

 fork. Two typical curves showing this effect are given in 

 figs. 2 & 3 ; the abscissae denote distances from the plate, and 

 the ordinates represent the apparent wave-lengths magnified 

 ten times. The numbers denote centimetres. 



