1909.] Elasticity of Rubber Balloons and Holloiv Viscera. 487 



was the same as that of the air admitted at atmospheric pressure. f With the 

 exception of the early stages of inflation and last stages of deflation, when 

 the radius approached the initial value, the halloon could be regarded 

 as a true sphere. As, further, the greatest pressure within the balloon was 

 always a negligible fraction of the prevailing atmospheric, I have not 

 thought it necessary to make any calculated correction as to the volume of 

 the contained air. 



When experiments were performed on a hollow viscus, some water was 

 placed in the partially immersed flask, and a few drops placed in the interior 

 of the viscus itself so that the air within and without should be saturated 

 with water vapour. 



Experiments on Balloons. 

 When air was admitted in measured increments to a fresh balloon, and 

 the reading taken a definite time (three minutes) after entrance of each 

 increment, it was found that the pressure rose quickly to a maximum and 

 then on continued inflation fell slowly. This is typically exemplified in the 

 experiment illustrated graphically in fig. 2. 



Z40 



1 2. 3 4 5 6 7 8 9 



Radius in centimetres 

 Fig. 2. 



It will be seen from this experiment that, over a considerable range, two 

 values of radius can be given for each value of pressure. This can be 

 demonstrated as a class experiment in the following way : Two balloons of 



2 N 2 



