iNTROfiUCTlOK* XXxl 



ings very near to each other, he was ena- 

 bled to form a proper plan for accomplifh- 

 ing the obje^ of his wifhes, and by means 

 of gunpowder he broke to pieces, tinder the 

 water^ that part of the bank which ob- 

 ftru£ted the paffage of veflHs* 



No rock can refift the expanfive force of 

 an elaftic fluid, when the engineer who 

 employs it knows, by holes difpofed at fuit- 

 able di (lances, to interrupt the communica- 

 tion of motioa in fuch a manner as to 

 render the force proportional to the mafe. 

 It is really aftonifhing that gunpowder is fo 

 little ufed for extirpating rocks under water, 

 a$ there is no force greater or lefs expenfive 

 when it is dirfeed by intelligeDt men* 



Had M. de Tromelin been acquainted 

 with the iogcmous method devifed by M* 

 Coulomb, a celebrated academician, for la- 

 bouring under water, that able officer would* 

 doubtlefs, have made ufe of it; and this 



grand 



