1^2 ADHESION OF BODIES TO FLUIDS. 



pose to their separation, equal to the weight of a cylinder of 



water, the base of which is the surface of the disk, and its 



altitude the height to which water would rise between two 



parallel planes of glass, as distant from each other as the 



the're^stimce interval that separates the disks. Mr. Guy ton de Morveau 



much greater made an experiment of this kind with two disks of glass, the 



than it should diameter of which was 81-21 millimetres [3*18 inches], and 

 have been by . L J 



theory, he found their resistance to separation 250*6 grammes 



_[3870*5 grs.]. According to the preceding theorem, the re- 

 sistance would be only 155*78 grammes [240C grs.]. The 



from rmstak- difference of about one third between these two results, 



nig their dis- T i • i •• r» i • 



tance, arose, no doubt, either from the estimation ot the interval 



that separates the disks, which requires great nicety in such 

 or inequalities small intervals ; or to the inequalities of the surfaces of the 

 of their surface, disks, which it is difficult to render accurately plane. 

 Theory of ^ ne su^tentation of small bodies on the surface of fluids 



small bodies depends on this general principle : " The diminution of 

 flukS 1 ^ ° n -weight of a hof h merging in a fluid, that sinks around it 

 by capillary action, is the weight of a volume of fluid equal 

 to that of the part of the body beneath the level, added to 

 the weight of the volume of fluid displaced by capillary ac- 

 tion. If this action raise the fluid above the level, the di- 

 minution of weight of the body is the weight of a volume 

 of the fluid equal to the part of the body below the level, 

 minus the weight of the fluid raised by capillary attrao 

 tion." 

 Diminution of This principle embraces the known hydrostatical prin- 

 weight of bo- ciple of the diminution of weight of a body plunging 

 into a fluid : it is sxtffieient to omit what relates to capillary 

 action, which totally disappears, when the body is com- 

 pletely in the fluid below the level of its surface. 

 Demonstra- To demonstrate the principle just laid down, let us sup- 



not) of this p OSe a vertical tube large enough to include the body itself, 

 {irmciule. ' , , . ° , . . , 



and all the body ot fluid that it sensibly raises, or the space. 



it leaves empty by capillary action. Let us conceive this 

 tube, after having penetrated into the fluid, to bend hori- 

 zontally, and afterward rise vertically, preserving the same 

 ■diameter throughout its whole extent. It is clear, that, in 

 the case of an equilibrium, the weights in the two vertical 

 branches of the tube must be equal. The weight of the 



body 



