350 Hydrostatics. 



Fi 22-7 ( 2> ) ^ t ^ le two Bodies are f sucn a nature as not to suffer the 

 fluid to adhere to them, as is the case with balls of iron used in 

 connection with mercury, the same phenomena will be observed. 



^ " ' (3.) But if one of the bodies is susceptible of an adhesion of 

 the fluid, and the other not, as two balls of cork, for example, 

 one of which has been carbonized by the flame of a lamp; the 

 effect will be the reverse of that above stated ; that is, the bodies 

 will seem to repel each other, when brought very near together, 

 and with forces similar to those with which in the former case 

 they tended to unite. 



Moreover, a single ball will approach to, or recede from, the 

 side of the vessel, as it would approach to or recede from another 

 ball, according as the substance of the vessel and that of the 

 ball are similar or dissimilar as to their disposition to cause an 

 adhesion of the fluid. 



465. Tn these experiments the approach and recession of 

 the floating bodies are not the effect of a real attraction or repul- 

 sion between the bodies ; for, if the bodies, instead of being plac- 

 ed upon the surface of a Jiquid, be suspended by long, slender 

 threads, nothing of the kind is to be perceived. We must there- 

 fore look for some other cause to which to refer these appearan- 

 ces. 



Fig.229. If two plates of glass AB, CD, be suspended in water paral- 

 lel to each other, and at such a distance, that the point H, where 

 the two curves of elevated fluid meet, sha^ll be on a level with 

 the common surface, the plates will remain in equilibrium But 

 on being brought so near to each other, that the point H shall 

 be above the common level of the surface, the mass of fluid thus 

 raised will have the effect of a chain attached at its extremities 

 to the plates, in drawing the plates toward each other. The 

 approach of the balls to each other under similar circumstances, 

 is to be referred to the same cause. 



When the point H is below the general level, on account of 

 a want of adhesion in the parts of the fluid to the plates, the 

 pressure of the plates inward toward each other not being coun- 

 terbalanced by the pressure in the opposite direction, they must 

 approach each other, and with a greater or less force, according 



