TRANSACTIONS OF THE SECTION. 



181 



Table I. 



First Series of Experiments on Absorption, under a pressure of 20,000 lbs. per 



square inch, reduced to 100 hours' exposure, and 10 inches area. 



Reduced results. 



Insulator. 



2 • 



■ c 



fc 



"5 £ 



p 



3 3 



8 ° 



3,— 



c„ ...a 



India-rubber 



India-rubber with carbon 



Wray's compound 



Gutta percha 



20,000 

 20,000 

 20,000 

 20,000 



8-720 

 8-720 

 o-720 



8 



•720 



100 

 100 

 100 

 100 



10 

 10 

 10 

 10 



0-177 

 0055 

 0-072 

 0044 



The temperature in all these experiments was low, sometimes several degrees 

 below the freezing-point. In the first experiment with Wray's compound, the 

 cylinder when opened was found to be filled with loose ice. 



In the next series the whole of the specimens were placed in the same cylinder, 

 and remained under pressure during the same period, and under the same condi- 

 tions. 



Table II. 

 Experiments on Absorption, under a pressure of 6000 lbs., and at the ordinary 



temperature. 

 Reduced results. 



The order of merit in resisting absorption, as derived from this series of experi- 

 ments, is — 



1. Vulcanized india-rubber. 5. Wray's compound. 



6. Carbonized mdia-rv 



2. Chatterton's compound. 



3. Gutta percha. 



4. Masticated india-rubber. 



6. Carbonized india-rubber. 



7. India-rubber not masticated. 



The next series of experiments was made under greater pressure, but in the 

 same manner and for the same period of immersion. 



