VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 437 



this subject, are easily explicable. For on a careful examination, it will be 

 found in them all, that some parts of the water quit the contact of the other 

 water, and join themselves to the glass. 



Prop. 6. The Particles of Quicksilver are more strongly attracted by each 

 other, than by Glass. Exper. 1. — If a small tube as ab, fig. 5, open at both 

 ends, be dipped into a glass vessel filled with mercury, and be held close to the 

 side of the vessel, that the rise of the mercury within it may appear ; the mer- 

 cury will partly enter into the tube, but will stand within it at some depth, as 

 CE, below the surface of the quicksilver in the vessel, cd ; and this depth will 

 always be reciprocally as the diameter of the tube. 



In this experiment a column of quicksilver of the height ce endeavours to 

 force the mercury higher into the tube; and as glass has been already proved to 

 attract quicksilver, the attraction of the annular surface on the inside of the 

 tube, which is contiguous to the upper part of the mercury, will also conspire 

 to further its ascent. What opposes the ascent of the quicksilver, is the power 

 by which that part of it, which endeavours to rise into the glass, is drawn back 

 by the attraction of the other mercury, with which it is in contact laterally; and 

 this not only balances the attraction of the glass, but also the weight of the 

 column of mercury of the height ce, and consequently this attraction is con- 

 siderably stronger than the attraction of the glass. 



The cause therefore that suspends the weight of the column of mercury ce, 

 being the difference between the attraction of the annular surface of the tube 

 at E, and that of an equal surface of the quicksilver in the cistern, from which 

 the mercury that endeavours to rise into the tube, must recede, in order to 

 unite itself to such an annulus of the glass, will always be proportional to that 

 annular surface, or to the diameter of the tube. And since the column sustained 

 must be proportional to the cause that suspends it, that column must also be as 

 the diameter of the tube. But the column suspended is as the square of the 

 diameter of the tube and the height ce conjointly ; from which it follows, that 

 the height ce must be as the diameter of the tube reciprocally, as it is found to 

 be by experiment. 



The experiment of the ascent of water above the level in a capillary tube is 

 just the reverse of this. 



Exper. 2. — Quicksilver being poured into the inverted siphon acb, fig. Q 

 having one of its legs ac narrower than the other cb ; the height ce, at which 

 the mercury stands in the wider leg cb, is greater than the height cd, at which 

 it stands in the narrower leg ca. On the contrary, water stands higher in the 

 narrower leg, than in the wider. 



Exper. 3. — abcd, fig. 7, represents a rectangular plane of glass, being one 



