PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 907 



of erection would be accomplished by building on shore upon 

 scnft'olding, the trmsed chcnn, floating it to the intended site upon 

 pontoons, and raising it to its position by means of hydraulic presses, 

 precisely as was done with the Britannia bridge, and needs no 

 elucidation as to its feasibilty. In this work a torty horse engine 

 applied the power through a pipe ^ inch bore, into a cylinder 20 

 inches in diameter, having a ram 18 1 inches in diameter. I esti- 

 mate the cost in gold of the proposed bridge complete, with abut- 

 ments and pier, at $750,000. 



In the foregoing remarks our subject was necessarily handled 

 in a very sketchy manner, necessitated by the limits of my paper. 

 I aimed at being brief, and, in so doing, I may not have l^een as 

 clear in some points as you may have desired. In touching upon 

 existing examples, I have only done so in order that you may see 

 what has been done and, taking comfort thereby, we can better 

 comprehend what ma}^ be done. If I have been the means of 

 developing a few points for the intelligent consideration of the 

 subject now before the i)ublic, I am satisfied, and in retiring, I 

 beg leave to thank you for your kind attention to me this evening. 



At the conclusion of this paper the Association adjourned. 



American Institute Polytechnic Association, 



Ajjril 4, 18 G(). 



Prof. S. D. Tillman Chairman. T. D. Stetson, Esq., Sec'y. 



The following notes on new discoveries and inventions were 

 presented by the chairman : 



Coal Near Mobile. 

 The newspapers of Moljile, Ala., announce the discovery of val- 

 uable veins of coal within a convenient distance to that city. 



To Prevent the Fading of Photographs. 

 It is well known that the spontaneous decomposition of the 

 h^'posulphites used in fixing the photographic picture is one of 

 the chief causes of fading. Several processes have been proposed 

 for remedy i.ng the evil but none seem to have answered the purpose. 

 Reccntl}^ Messrs. Tichborne and Robinson, of Dublin, Ireland, 

 have devised a process to eliminate the hyposulphite without pro- 

 ducing any counterbalancing injury. It consists in washing the 

 print in a bath composed of a mixture of baryta and perchloric 



