198 On Capillary ASl'ion. 



If a capillary tube be infcrted through another tube, and 

 both dipped in water, it will rife not only in the capillary 

 bore, but in the interlace between the two tubes. Even 

 though the diameter of the outer' tube be conliderable, the 

 water muft form a fenfible elevation in the intermediate ring; 

 and this elevation will be determined by comparing the ex- 

 tent of the oppofite furfaces of glafs with the intercluded fpace 

 on which their attion is fpent. The abfolute afcent in the 

 capillary bore continues the fame; but, if we eftimate it from 

 the external protuberant ring of water, it will appear evi- 

 dently diminifhed. Conceive the outer tube to be fitted with 

 a bottom, and the whole to be removed from the bafin : the 

 effect will ftill remain the fame, and confcquentlv the appa- 

 rent altitude of the fluid in the capillary bore will he dimi- 

 nifhed. Let J denote this bore, d" the diameter of the tube, 

 and J" the width of the outer tube, or rather that of the cif- 

 tern in w hich the capillary is plunged : then it may be cafily 

 invelVigated, from the principles already explained, that the 



heiirht to which the water will rife is = — - (—- ; 



' ,,, _ ,J in inches. 



Tf the tube has its lower orifice not too wide, on removing 

 it from the ciflern in which it was immerfed, a drop of water 

 will adhere, and the column in the capillary bore will remain 

 at the fame height. Its fufpeufion, we have feen, is pro- 

 duced by the lateral adhefion of the internal film, to which 

 a cylinder of water attaches itfelf. If the drop at the extre- 

 mity be diminifhed by any caufe, fuch as the contaft of 

 bibulous paper, the column will fubfide; for the tendency 

 of the water to agglobulate then counterafts, in fome degree, 

 its capillary extenlion in the tube. Cover a horizontal piac-e 

 of glafs with a fine film of water, and bring the tube with 

 its charge to touch it, the water will immediately defcrt the 

 cylindrical cavity and fpread over the film. 1 he attraction 

 which the vertical column of water, joined to its weight, bears 

 to the cxpanfive horizontal film, overcomes its adhefion to 

 the narrow film that lines the infide of the tube. We here 

 contemplate th.' extreme cafe ; but it fliould be remarked in 

 general that the mutual attraction of the particles ot water or 

 other fluids muft, to a certain decree, diminifli their afccut 

 in capillary tubes, fince that force tends to agglomerate the 

 parts, and confequently oppofes any ramifications or fila- 

 mentous prolongations of the fluid. This refillancCj it might 

 7 ^be 



