2/6 Mr. Wm. Thomson and Mr. F. Lewis on 



dyed cloth, which, he said, were produced by the same manu- 

 facturer, and proofed by two different proofers. He said he 

 had heated part of them to 1 50° Fah. f Dr a week, and they 

 had not become injured in any way. Both pieces were 

 analysed and found to contain — 



Percentage of 

 Copper Oxide. 



India rubber water-proofed cloth (a) o* 1 90 



» ,) ip) o-io8 



— ^- — cloth before proofing {c) "370 



The oily and greasy matter in cloth before 



proofing amounted to 4*200 % 



Wishing rapidly to arrive at a conclusion as to the 

 influence of the copper oxide on the rubber, we heated 

 pieces of both at the temperature of boiling water for 12 

 hours along with two other pieces which were 2 and 5 

 years old respectively, and at the end of that time the 

 rubber on the cloth containing copper was in the one 

 damaged and in the other destroyed, whilst that on the 

 two free from copper was quite sound. 



We might give still another instance in which some 

 black, brown and white check proofed cloth, the rubber on 

 which had become oxidised and hard, was analysed by one 

 of us and found to contain 0*24 per cent of copper oxide : 

 he afterwards obtained some unproofed cloth of the same 

 kind, which he divided into three parts, one he left in its 

 original condition, from one he extracted oily and greasy 

 matters, and from the third he removed the copper as well 

 as the oily and greasy matters ; the three were joined 

 together and covered with a continuous sheet of pure Para 

 india-rubber by one proofer, and a second portion of these 

 three pieces, joined end to end, was covered with a continuous 

 sheet of ordinary rubber composition, containing lampblack, 

 zinc oxide, and other mineral compounds, by another 

 proofer. On heating these for 14 days in the incubator at 



