238 NEWTON S PRINCIPIA. 



lighter ones, which fell slower. Every care was taken to 

 diminish these oscillations, but they could not be alto 

 gether prevented. 



From the top of St. Paul s, in June, 1710, two glass 

 globes were allowed to fall through the height of 220 

 English feet. One was full of quicksilver, the other con 

 tained air. The two globes rested on a wooden table, which 

 turned round iron hinges on one side, the other side being 

 supported by a wooden pin. The two globes were let fall 

 together by pulling out the pin by means of an iron wire 

 reaching from thence quite down to the ground, so that 

 the pin being removed, the table, which had then no sup 

 port but the iron hinges, fell downwards, and turning 

 round, the globes dropped off it. At the same instant 

 with the same pull of the iron wire that took out the pin, 

 a pendulum, oscillating seconds, was set in motion. The 

 wooden table was not found to turn so quickly on its hinges 

 as it ought to have done. Hence the times of descent 

 were prolonged 3&quot;. This must be taken into account, as 

 in that time the ball full of mercury would have described 

 37 feet. The difference between theory and experiment 

 was found to be very small. To mention one instance, one 

 globe of air fell 220 feet in 8.2&quot;; according to theory it 

 should have fallen in that time 225 feet 5 inches. The 

 resistances to the globes of mercury were found to be so 

 small in comparison with their weight, that they fell in 

 nearly the same time which they would have taken to fall 

 through the same height in vacuo. The differences could 

 not be observed with sufficient accuracy to furnish a test 

 of the theory, the difference being sensibly the same for 

 globes of all weights. 



In July, 1719, Dr. Desaguliers made some other 

 experiments of the same kind. The globes let fall were 

 formed of hogs bladders blown full of air. They were 



