614 



Scientific Proceedings. Royal Dublin Society. 



When the values of b are plotted against the area, as in fig. 2, a straight 

 line graph is obtained which intersects the axis of x in a point lying to the 

 left of the origin. Hence the absorption is not directly proportional to the 

 area of the bubble. This appears to be due to the fact that the conditions 

 which apply to the cylindrical portion of the bubble do not hold for the 

 hemispherical head. The rate at which the water streams past the head of 

 the bubble is much less than that at which it passes down the cylindrical 

 portion of it ; hence the absorption due to the head of the bubble is greater 

 than might be expected from its area. These two effects are differentiated 

 by measuring the rate of absorption for a number of different bubbles ; 



20 30 40 50 ( 



Fig. 2. — Area in sq. cm. 



Values of b plotted against area of bubble. 



because, since the effect of the head of the bubble is the same in each case, 

 the variation in absorption must be due to variation in the area of the 

 cylindrical portion. Hence the graph shows the rate at which the value 

 of b increases with increasing cylindrical area. By producing the graph 

 until it cuts the «-axis we obtain a constant correction for the head of the 

 bubble, which, when added to the calculated area of the bubble, gives the 

 effective area when the absorption is uniform all over the surface. 



The value of the intercept on the ai-axis is 15 sq. cm. ; hence this amount 

 must be added to the area of each bubble. 



