32 Proceedings of the American Philosophical Society. 



Mr. Peale exhibited specimens of medals obtained by the process of 

 Prof. Jacobi. He stated that Mr. Eckfeldt, of the Mint, had found the 

 specific gravity of the copper thus procured, to be as high as that of rolled 

 copper, that is, 8.95. 



Mr. Peale also exhibited a diaphragm of parchment, which had been 

 used in the battery employed in the process; and upon which metallic 

 copper had been precipitated. He farther exhibited specimens of metal- 

 lic silver, reduced, by a similar process, from the chloride of silver ; but 

 remarked, that it was not likely to lead to any useful analogous result, 

 owing to the silver being deposited in a granular state. 



April 3. — The committee, consisting of Dr. Patterson, Dr. Hare, and 

 Prof Bache, to whom was referred a paper entitled " On a new Principle 

 in regard to the Power of Fluids in Motion to produce Rupture of the 

 Vessels which contain them, and on the Distinction between Accumula- 

 tive and Instantaneous Pressures ; by Charles Bonnycastle, Professor of 

 Mathematics in the University of Virginia," reported in favor of its pub- 

 lication in the Transactions of the Society, which was ordered accord- 

 ingly. 



Mr. Bonnycastle's investigation was suggested by a paper read by Dr. 

 Hare, and printed in the Transactions of the Society, entitled " On the 

 Collapse of a Reservoir, whilst apparently subject within to great Pressure 

 from a Head of Water." Dr. Hare pointed out the circumstances at- 

 tendant upon this curious occurrence, and showed how the vessel might 

 have been momentarily relieved from the pressure of the water within, so 

 as to make that of the surrounding air efficient in producing the collapse. 

 The principal object of Mr. Bonnycastle's paper is to investigate the pre- 

 cise nature and degree of the forces brought into action in this and simi- 

 lar cases. 



The results at which Mr. Bonnycastle arrived, are stated by him as 

 follows : — 



1. It is convenient to distinguish between accumulative and instanta- 

 neous loads, or between those which are gradually increased until the 

 deflection due to the ultimate load is obtained, and those which commence 

 in full efficacy from the initial position of the support. 



2. Within the limits of perfect elasticity, instantaneous pressure pro- 

 duces twice the effect of that which is accumulative, whether the result 

 be to produce deflection or fracture. 



3. In regard to supports perfectly elastic in one direction, and perfectly 

 flexible in the other, instantaneous action, at right angles to the axis of 

 elasticity, produces a deflection which is to that of accumulative action 

 as ^74 to 1, whilst the tendencies to fracture are as 4 to 1. But should 

 any case occur when the law of elasticity follows an extremely high power 

 of the deflection, then the singular result will follow, that the deflections 

 are the same, whether the force be exerted from the initial state or the 



