ARTICLE XL 



On a new Principle in regard to the Power of Fluids in Motion to produce Rup- 

 ture of the Vessels which contain them ; and on the Distinction hetween accu- 

 mulative and instantaneous Pressure. By Charles Bonnycastle, Professor of 

 Mathematics in the JJ7iiversity of Virginia. Read November 15, 1840. 



In a paper published by Dr. Hare in the Transactions of the American Phi- 

 losophical Society, of which paper he was polite enough to send me a copy, is 

 a description of a singular phenomenon that was observed in the destruction of 

 an air-vessel, under circumstances which at first appear to contradict the known 

 laws that regulate the motion and pressure of fluids. 



The subject of the paper is " The collapse of a reservoir whilst apparently 

 subject within to great pressure from a head of water;" and in treating it, Dr. 

 Hare points out the attendant circumstances, and ingeniously shows how the 

 vessel may have been momentarily relieved from the pressure of the water 

 within, so as to make the pressure of the surrounding air efficient in producing 

 the collapse. He does not, however, push his inquiries to a point essential to 

 the full explanation. An investigation into the nature and degree of the forces 

 brought into action leads to results, according, indeed, with the theory of resi- 

 lience, but presenting, in the laws of instantaneous pressure, and in the effects 

 of that pressure when produced by an abrupt check given to a fluid in motion, 

 a branch of the subject in some degree intermediate between statics and dyna- 

 mics, and which has not yet been fully developed. 



At the period when I first deduced the results contained in this paper, very 

 little attention had been paid to any of the class of phenomena to which they 

 belong; something further has since been done in England, but I have not seen 



VII. — 2 D 



