600 PHILOSOPHICAL TRANSACTIONS. [aNNO 1722. 



incumbent column of water; for, it is impossible for the column of water to 

 press on the subjacent drop without being hindered in its descent by that drop; 

 but it is not hindered, because it does not endeavour to descend with greater 

 velocity than the lowest drop tends downwards by its own force of gravity; for 

 the column and drop descend equally; so that the drop will neither quit the 

 column, nor receive any force or pression from it. 



The Doctor therefore thinks Bernoulli's demonstration falls to the ground; 

 his mistake seems to be owing to his not adverting to the difference between a 

 body pressed on by an incumbent weight, when that weight is only urged by 

 the natural accelerating force of gravity, and a body impelled, or animated, as 

 he calls it, by the accelerating force of gravity, preternaturally increased: in 

 the latter case, the body will descend with a greater velocity than what can be 

 produced by the natural force of gravity, according to Bernoulli himself; but 

 in the former case, however, the body pressed upon, while it is at rest, may 

 be urged by the incumbent weight; yet as soon as it begins to descend, it will 

 do so entirely with the same degree of velocity, as if it were not pressed on by 

 any incumbent weight. 



To illustrate this by an example: suppose a solid column, consisting of 100 

 pieces of gold, laid upon each other, at rest on a table, and the lowest piece 

 pressed on by the weight of the rest; now if a hole be made in the table, 

 under the pieces, that the undermost may slip through ; as soon as it begins to 

 fall, it is immediately freed from the weight of the incumbent pieces; and then 

 the undermost piece, and all the rest will descend, with the same velocity as 

 if there were only that lowest piece on the table. 



If from the velocity with which, according to Bernoulli, water runs out at a 

 hole, and from the mass of water, as determined by that velocity running out 

 in any given time, any one would determine its motion, he would find it twice 

 greater than what could be produced by the force of gravity, from the weight 

 of the column of water inciKnbent on the hole. 



The Doctor recommends the two following experiments, in order with more 

 certainty to determine the controversy, either to be tried a-new, or at least 

 diligently considered; the one is Sir Isaac Newton's, described p. 305, Princip. 

 second edit. viz. From the mass of water, running out in a given time, to 

 find the velocity with which it passes through the hole; the other is Mariotte's, 

 in his book De Mouvement des Eaux, part 2, disc. 3, regl. i, and made with 

 a cylindrical pipe, open at both ends, its lower part turned upwards, and full of 

 water; whence it may be easily estimated, whether the first drops of effluent 

 water can rise to so great a height, as Bernoulli's demonstration requires. 



