394 Lord Rayleigh on the Tension of Water 



after rinsing was filled with water drawn from a tap in con- 

 nexion with a cistern supplied mainly by rain water, and 

 placed in position. On expansion of the brass hoop the 

 number of waves included between the measuring points was 

 estimated to be 13*7, 13'8 by the two observers. A piece 

 of paper was then greased with oleic acid, and with this a 

 platinum wire, previously cleaned by ignition, was wiped. 

 On introduction of part of the wire into the water contained 

 within the hoop, the number of waves rose to 15*4, 15*3. 

 Upon this surface camphor scrapings were found to be quite 

 dead, so that the mark had been overshot. 



The dish was then refilled. Upon expansion the number 

 of waves upon the clean surface was 13*7, 13*7. On con- 

 tamination with a little oleic acid, 14*8, 14*8. Camphor was 

 now moderately active. More oleic was added. Readings 

 were now 15*4, 15*4, and camphor was quite dead. 



The point to be fixed evidently lay between 14*8 and 15*4. 

 A fresh surface was taken, and on addition of a little oleic the 

 readings were 14*8, 14*8. Camphor was then tried and found 

 moderately active. Reading still 14*8. A little more oleic 

 added ; readings 15*1, 15*1 ; camphor scrapings were now 

 " nearly dead." More oleic ; 15*2, 15*2 ; camphor " very 

 nearly dead." More oleic; 15'4, 15*4; "not absolutely 

 dead." More oleic ; 15*5, 15*5 ; camphor " absolutely dead." 

 The temperature of the water was 63° F. 



On a previous occasion (July 29) accordant results had 

 been obtained. Clean water 13*7, 13^7. Oleic added ; 15*0, 

 15*0; camphor nearly dead. More oleic; 15"2, 15'25 : 

 camphor Very nearly dead. Oleic; 15*55, 15*6 ; camphor 

 dead. On both days the distance over which the waves were 

 measured was 9*20 centim. 



It may be well to exhibit in full the calculation for the 

 clean water : — 



log 9-2 = -9638 logg = 2*9917 



log 13-7 = 1-1367 W\ =1-8271 



log X = 1-8271 



1-8271 



3 



logX 3 =1-4813 



log 42*12= 1-6245 



1-6245 



2-6459 

 log 4tt 2 = 1-5962 



log 11-2 = 1-0497 



2-7303 

 log 2tt = -7981 





log 85-5 = 1-9322 



Finally, T = 85-5-11-2 = 74-3. 



