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we muft allow that whatever be the force of gravity wherewith' 

 the uppermolt plate prtiles upon the fecond, the fecond prefTes 

 bn the third with a double force, and the third upon the fourth 

 with a triple force, and fo on; fo that the plate which is next 

 the orifice is preifed downward by the joint gravities of the 

 feveral plates which lie above it, and likewife by the force of its 

 own gra^^ity, inafmuch as there is no other- plate beneath it 

 whereon to reft; confequently from its own gravity, and that of 

 the feveral plates above it, it does all at once receive as many 

 equal impreiTions from gravity, as it would fuccefTivcly in falling 

 down the height of the water ; and of courfe muft pafs through 

 the orifice with the fame velocity that it would acquire in falling 

 down that height., 



This dembnftratiori appears to be defe£tive in this refped^ 

 that it does not take into account the time in which the 

 force accelerating the difchargc of the water ads; for it is evi- 

 dent, that the greater the velocity with which the loweft plate 

 of water is difcharged through tlie orifice the fhorter will be 

 the time during which it is accelerated by the preffure of the 

 incumbent flaid. By negleding this circumftance, it would 

 follow, from Doctor Helflmm's feafoning, that the velocity fliould 

 be in the diredt fimple, not fubdnplicate ratio of the height of 

 t4ie fluid, the velocity generated being, ceteris faribus^ as the 

 accelerating force, that is, as the height of the column of water 

 ftanding diredly above the orifice. If, indeed, this time be taken 

 into confideration, the inference will be legitimate. Thus the 

 velocity generated in the iffuins; plate of water will be as the 

 accelerating force^and the time of its adion conjointly, the plat«, 

 that is, the quantity of matter moved, being given ; but the time 



