PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION, 651 



lighter color, and therefore of receiving quite brilliant tints. 

 The lighter color arises from the fact of rubber being less ex- 

 posed to the atmosphere during the process, which exposure, in 

 Goodyear's process, turns the product almost black ; and to 

 make it lighter, zinc white, or some other kind of white material, 

 is required to be added. Mr. S. exhibited some very beautiful 

 specimens of colored rubber made by this new process, and, 

 among others, a globe containing a map of the world, which, the 

 President said, Goodyear, after much experimenting, was unable 

 to produce. Mr. S. also exhibited some milk of the rubber 

 tree, ammonia being added to it to preserve it in a liquid state. 

 The milk in the bottle was perfectly white. 



The President stated the fact that india-rubber car-springs 

 were passing out of use. It was found that the jolting of the 

 car caused the india-rubber at last to lose its elasticity. 



Mr. Churchill exhibited some pieces of vulcanized rubber 

 which had been subjected by him to mechanical tension, and the 

 action of steam for the space of about three hours. The result 

 was that the rubber was perfectly brittle. 



SELF-ADJUSTING SUBMISSIVE SPRING. 



J. M. Forrest, of Virginia, exhibited and explained a carriage 

 spring with the above title, which he had patented. It consists 

 of several leaves of steel, like the elliptic-spring, but the form is 

 entirely different. The advantages claimed over the elliptic 

 spring are these : — First, there is only one hole drilled through 

 the leaves, which is necessary to fasten it, with the addition of 

 two clasps, to the axletree. Second, there is no welding, and 

 therefore it is less troublesome to the manufacturer. Third, the 

 spring divides the weight equally on the axletree, thereby ren- 

 dering the axletree less liable to break. Fourth, it is self-adjust- 

 ing, springing its entire length with a light weight. Fifth, it is 

 rendered submissive by a cross bar attached by hinges to the 

 end of each spring. Sixth, it weighs much less than the elliptic 

 spring, and therefore costs less. Mr. Forrest stated that he had 

 in a carriage with a spring weighing only fourteen pounds, driven 

 the horse, and written a letter at the same time. He regretted 

 to say that he had come north in order to get the springs made, 

 and he did not succeed in finding a man who could make what 

 he wanted till he got to New Haven, where he found a very inge- 

 nious Dutchman that did it. 



