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WITH DRY HEAT. 209 



SO far as my experience has gone, that porosity is 

 produced from three causes — defect in packing, 

 the bad quality of the rubber, or excessive heat 

 with hydrogen ; and I believe it will be generally 

 found that these are the principal causes of defect. 

 As touching my apparatus, I would observe, that 

 there is only sufficient moisture to prevent singe- 

 ing, and not sufficient to produce the sulphurous 

 hydrogen gas which causes the porosity of the 

 rubber. Where the generation of that gas is pre- 

 vented, whether by this patent or by any other 

 process, the process of vulcanization is extremely 

 simple ; but the statement that was first promul- 

 gated, that high pressure only was necessary, I 

 pronounce to be a fallacy. There is only one way 

 of producing pressure, in even a high-pressure or 

 a steam apparatus of any kind, and that is by 

 attaching a spring as I have done here [exhibiting 

 his improved patent flask]. Here is a small 

 cap, and by attaching a spring we then have a 

 gradual pressure during the fusion of the rubber. 

 You take one of my flasks, and we thus have a 

 pressure which can be regulated by a screw. Now 

 one would really think that a heat of 300°, or even 

 350°, in this apparatus, would soften this spring, 

 but as it is not sufficient to singe paper, it 

 certainly will not destroy the temper of the 

 spring. In the early stages of the process of 

 vulcanizing, you have an immense pressure while 

 the rubber is yet partially fluid ; and when the 



