CAPILLARY ATTRACTION. 



143 



causes liquids to ascend above their level in capillary tubes. Fig. 129. 



It, however, is not strictly correct, as this force not only acts 



in elevating but in depressing liquids in tubes, and is at 



work wherever liquids are in connection with solid bodies. 



324. If a Uquid be poured into a vessel, as 

 water in glass, whose sides are of such a naturo 

 as to be wetted by it, the liquid will be elevated 

 above the general level of its sui'face at the 

 points where it touches the sides of the ves- 

 sel This is shown in Fig. 130. 



If, however, the liquid is poured into a 

 vessel whose sides are of such a nature that 

 they are not wetted by it, as in the case of 

 quicksilver in a glass vessel, then the liquid 

 will be depressed below the general level of its surface at the 



What will be 

 the condition 

 of the surface 

 of a liquid 

 which wets the 

 sides of the ves- 

 gel containing 

 iJ.' 



When the liq- 

 uid does not 

 wet the sides 

 of the vessel, 

 what will be 

 the condition 

 of its surface ? 



Fig. 130. 



Fig. 131. 



points where it comes in con- 

 tact with the sides of the ves- 

 sel. This is shown in Fig. 131. 

 325. If two plates of glass, 

 A and B, Fig. 132, be plunged 

 into water at their lower ex- 

 tremities, with their faces ver- 

 tical and parallel, and at a cer- 

 tain distance asunder, the water will rise at the points m and n, where it is in 



contact with the glass; but at 

 Fig. 13... all intermediate pomts, beyond 



a small distance from the plates, 

 the general level of the surfaces 

 E, C, and D, will correspond. 



If the two plates, A and B, 

 are brought near to each other, 

 as in Fig. 133, the two curves, 

 "~ — . m and n, will unite, so as to form 



a concave surface, and the water 

 at the same time between them will be raised above the general level, E and 

 D, of the water in the vesseL If the plates 

 be brought still nearer together, as in Fig. 134, 

 the water between them will rise still higher, 

 l.ie force which sustains the column being in- 

 creased as the distance between the plates is 

 diminished 



326. The heiglit to 



which water will rise in — • 



capillary tubes is ia proportion to the small- 

 ness of their diameters. 



To what is the 

 elevation of 

 water in capil- 

 lary tubes pro- 

 portioned ? 



