VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 287 



with little letters) the cork had added to it three quarters of the weight of the 

 antimony which the hand before had sustained, and made it sink so as to be 

 almost covered, and raised the water to ik, adding 3 ounces to its weight. 

 Suspending this vessel of water to the balance, and a counterpoise at the other 

 end, on cutting the string, the vessel of water was raised up, and the equili- 

 brium was not restored till the antimony came to the bottom. 



By observing that as the cork (being freed from the weight of the antimony) 

 rose, and that during the fall of the body, the water sunk to hh, it appears that 

 this is, in effect, the same experiment as the former, and concludes no more. 

 As to the real cause of the variation of the barometer, namely, the accumula- 

 tion of the air by winds over the place where the barometer rises; and part of 

 the air being blown away where the Mercury in the barometer sinks, see Doctor 

 Halley*s account of it in the Phil. Trans. N^ 181. 



In making the first experiment before the Royal Society, of a piece of lead 

 suspended by a thread, while it was wholly covered with water in the large 

 tube in which it hung, whose length was 4 feet, it was observable, not only 

 that the end of the balance (to which the tube of water with the lead in it was 

 fixed) did not rise when the thread was cut, to let the lead fall from the top to 

 the bottom of the tube, as it must have done according to Mr. Leibnitz's 

 principle ; but that the said end of the balance began to descend from the time 

 that the lead began to fall. Therefore, to be assured that it was not the 

 plummet's rubbing against the sides of the tube in its fall, which caused that 

 phenomenon, I hung to the balance a long glass of 3 inches diameter, instead 

 of the tube, and making the experiment as before, it succeeded in the same 

 manner : the end of the balance which carried the vessel of water sunk as soon 

 as the thread of the plummet was cut ; though this glass was not above half so 

 long as the tube. 



When by holding the string I drew the lead upwards and downwards in the 

 water, there was no sensible alteration of the equilibrium. Neither was it 

 altered by cutting the string of a stone plummet, because of the shortness of 

 the glass, and the little excess of specific gravity in the stone : for the greater 

 the difference is between the body used in this experiment and water, as well 

 as the larger the body itself is, the better the experiment will succeed. 



Hence it appears, that when a body, specifically heavier than a fluid, is by 

 any cause whatever detained in any place of the said fluid, it adds as much to 

 the weight of the whole fluid as an equal bulk of the said fluid amounts to : 

 and when the said body, by the action of its excess of specific gravity above 

 the fluid, descends with an accelerated motion ; so long as that motion is acce- 

 lerated, the resistance of the fluid, which is as the square of the velocity, takes 



