638 PHILOSOPHICAL TRANSACTIONS. . [aNNO 1723. 



the said garden the preceding year, which are all to be specifically distinct from 

 each other, until the number of 2000 plants be completed. 



Accordingly the company lately presented to the R. S. by the hands of Mr. 

 Rand, and Mr. Meres, 50 specimens of plants, for the last year 1722; which 

 specimens, together with those that are to follow them in subsequent years, 

 will, by order of the R. S. be carefully preserved for the satisfaction of such 

 curious persons, as may desire to have recourse to them. Then follows the 

 catalogue. 



Animadversions on some Experiments relating to the Force of moving Bodies ; 

 with two new Experiments on the same Subject. By the ReV' Dr. Desaguliers, 

 F.R.S. N°376, p. 285. 



In the preceding N° I demonstrated, by reason and experiments, that the 

 momentum, or force of moving bodies, is always proportionable to their mass 

 multiplied into their velocity ; which is the opinion of most mathematicians 

 and philosophers. I now come to consider the experiments that have led some 

 ingenious men into an error, in regard to this proposition. Poleni gives an 

 account of his experiments relating to this matter, in these words : " I took a 

 vessel, that had in it congealed tallow 6 inches deep, and fixed it to a level 

 floor, in such manner, that the surface of the tallow, which was flat, should 

 every where be equally distant from the floor. I had caused to be made two 

 balls of equal size, the one of lead, the other of brass, the last of which was 

 a little hollow in the middle, that it might weigh but 1 lb. while the other 

 weighed 2. Suspending these balls from the ceiling by threads, in such a man- 

 ner, that the lighter ball hung over the surface of the tallow, from twice the 

 height that the heavier ball did ; I cut the threads, and the balls falling per- 

 pendicularly on the tallow, by their fall made pits in it, that were precisely 

 equal : the ball of 1 lb. from the beginning of its fall, till it came to rest, going 

 through a space expressed by the number 2, produced an effect equal to that 

 which the 2lb. ball produced, in falling through a space expressed by the num- 

 ber one. It follows therefore, that we may look upon it as a settled truth, 

 that the active forces (vires vivas) of falling bodies, are equal, when their pro- 

 per weights are in a reciprocal ratio of the spaces which the said bodies describe 

 by their fall. And because these spaces are in the same ratio, as the squares of 

 the numbers expressing the velocities ; it appears by the experiment, that the 

 active force (vim vivam) of the falling body, is that which is made up of the 

 body itself, multiplied into the space described in the fall, or into the square of 

 the number that expresses the velocity of the body, at the end of the motion. 

 This experiment I made several times, changing the balls, the distances, and 



