Allisn — The Insulating Properties of Erinoid. 



335 



more absorption of water than the black erinoid excepting at the initial stage, 

 shown by the curves, when the decrease is roughly the same in both cases. 

 The rate of decrease is seen to be comparatively large for the first 8 hours, 

 and much smaller after an immersion of 70 hours. 



Time in Hours. 



Fiq. 1. — Percentage decrease of resistance with time due to absorption of water. Curve A is 

 for red erinoid ; Curve B for black erinoid. 



At the end of immersion, the part of the sample tube projecting above the 

 surface of the water was found to be unchanged iu dimensions excepting close 

 to the surface of the water where its outer diameter had increased to an 

 appreciable degree which extended throughout the immersed length. This 

 swelling was more pronounced in the red than in the black erinoid. 



A test was also made on a tube of white erinoid. Its resistance in 

 megohms was found at several different temperatures in the dry state with 

 mercury inside and outside the tube. After immersion in water for 72 hours 

 the tube was taken out, carefully dried by rubbing it with dry cloths for 



