HYDROSTATICS. 191 



281. The reason why the water between the two 

 narrow plates of glass rises only to half the height 

 it does in a capillary tube, of a diameter equal to 

 the distance of the plates, is, that the quantity of 

 the attracting surface does not go all round, but is 

 nearly halved. 



a. The same holds of the tubes, inserted the one within 

 the other. Any small column of the water between 

 them, is supported by the attraction of the glass on- 

 ly on two sides. 



282. The adhesion of bodies to the surfaces of 

 fluids, is an effect of the same forces which produce 

 the phenomena of capillary tubes. 



a. This was first remarked by Dr YOUNG, Phil. Trans. 

 1805, and Lectures on Natural Philosophy, vol. n. 

 p. 652. The figure of the drops of a fluid support- 

 ed by a solid, or adhering to it, is connected with 

 the same phenomena. SEGNER treated of this sub- 

 ject, Comment. Soc. Reg. Gotting. torn. i. (1751) 

 p. 301. He considers the surface of the drops as 

 one formed like the catenarian curve, or like the 

 surface of a sail exposed to the wind ; and he as- 

 sumes the tension over all this surface to be the 

 same. LA PLACE remarks, that this supposition is 

 erroneous* 



b. The theory of LA PLACE, so far as the attraction 

 of the tube is concerned, has a great affinity to that 



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