364 PHILOSOPHICAL TRANSACTIONS. [aNNO I676-7. 



was contiguous to the water, than at the lower, that rested on the surface of the 

 oil of tartar. 



Having made these trials to alter, by another contiguous fluid than the air, 

 the concave superficies of water and some aqueous liquors, I proceeded to try 

 whether a change would not likewise be made on the convex figure of the sur- 

 face of quicksilver included in the like slender glasses; and accordingly having 

 taken one that was much longer, but of the like bore with the former, we put ^ 

 into it a small quantity of quicksilver, and having observed how the upper su- 

 perficies swelled in the middle above the level of the parts where it touched 

 the glass, we poured some water upon it, and found a manifest and considerable 

 depression of the surface, though the protuberance was not quite suppressed. 



This phenomenon having been for greater security several times repeated, I 

 thought fit to try, what variation would be made by the greater or less height 

 of the water incumbent on the mercury. And sometimes it seemed that when 

 the aqueous cylinder was much longer, the depression of the mercurial surface 

 was somewhat greater. But this did not so constantly happen, but we often 

 observed, that though a very little water sufficed by its contact to make, in the 

 judgment of the eye, a manifest abatement of the protuberance of the quick- 

 silver, yet it had not the same effect on that ponderous fluid that it had when, 

 being increased almost as high as the length of the pipe would permit, a greater 

 weight of it was incumbent on the mercury. 



Because the common atmospherical air we breathe is a fluid body abounding 

 with grosser particles, and is by divers philosophers probably supposed to be 

 much more dense and heavy than the aethereal substance, that makes the other 

 part of the atmosphere; I thought fit to try for their sakes, whether the super- 

 ficial figure of liquors would be altered by having the contiguous air withdrawn 

 from about them, and so being left to be touched by the purer ether without 

 it; and accordingly having conveyed into one of our pneumatical receivers a 

 couple of such slender pipes as have been already described, one of them fur- 

 nished with common water, and the other with quicksilver, we caused the com- 

 mon air to be pumped out, without observing any sensible change in the con- 

 cave figure of the water, but as for the quicksilver I knew not what to conclude 

 about it. For having repeated the trial twice or thrice, the mercury sometimes 

 seemed manifestly to swell and be more protuberant on the exhaustion of the 

 receiver, than when it was put in. But that which yet kept me doubtful was, 

 that I observed, that on the withdrawing of the air's pressure on the quicksilver, 

 there appeared in it some little bubbles, which I feared we had not been able 

 altogether to free it from, and which might be suspected to have some interest 

 in the phenomenon. I shall only add, that we conveyed into our receiver a 



