406 



Scientific Proceedings, Royal Dublin Society. 



quantity of moisture present, as indicated by the hygrometer, was approxi- 

 mately constant throughout each test. 



Three plates, one of red fibre, a second of red erinoid, and a third of blue 

 erinoid, were first tested. These were of equal size, 5'5 by 5'95 by - 5 cm., 

 and their surfaces were prepared in the same way. The surface of each plate 

 exposed to the- moist air was therefore 77 sq. cms. 



After the samples were heated for 144 hours at 70° C. in an air-oven they 

 were weighed, and the respective weights for red erinoid, blue erinoid, and 

 red fibre were found to be 26-95, 25'72, and 26-3 grammes. 



They were then immersed together in moist air, and taken out at intervals, 

 and weighed. During the test the two thermometers of the hygrometer 

 indicated a nearly constant difference of 0-3 C, and the reading of the dry 

 bulb thermometer varied only between 18° C. and 19° C. 



The results which were obtained are given in Table 1, and the corresponding 

 graphs in Fig. ] . 



Table 1. 



Table 1 and Fig. 1 show that red fibre is much more hygroscopic than 

 erinoid, and red erinoid somewhat more so than blue erinoid. Ked erinoid 

 was also previously found to absorb more water, when directly immersed in 

 it, than other varieties of erinoid. 1 From Fig. 1 and the initial weights, 

 previously given, of the samples, it follows that the percentage gain in 



1 Sclent. Proc. Roy. Dubl. Soc, 1918, vol. xv. (N.S.), No. 29, p. 332. 



