﻿382 M. G. Quincke on the Capillary Phenomena 



and the common surface of liquids o and u are then to be found 

 nearly in the same place of the capillary tube. h will then =0, 

 and 



u ou cos <o ou + ct cos (o — r,h u -^ (18) 



For the case in which G) ou =a) U) the phenomenon would be the 

 same as with the elevation of a liquid in a capillary tube, if the 

 capillary constant a of the one liquid were replaced by 



«cm + <* = a. 

 A very thin layer of liquid 2 upon a meniscus may considerably 

 modify and diminish the elevation of liquid 1 when 



If oil be placed on water, then, according to Table X. § 10, 



a 2 = 8*253 milligrammes, a J2 -|-a 2 = 5*856 milligrammes; 



thus a great depression of the liquid in the capillary tube must 

 take place when the oil is poured on, as Thomas Young* was the 

 first to observe. 



20. I made the experiments in a manner similar to that de- 

 scribed in §§4 and 16. Out of the purest thick glass tubing 

 glass threads of a suitable thickness were drawn by help of a 

 blowpipe-lamp. In the capillary tube thus prepared, open at 

 both ends, I allowed a column of liquid o to rise somewhat 

 higher than h was intended to be. The capillary tube with the 

 upper end closed was passed through two caoutchouc rings and 

 thus fastened to a strip of pure plate-glass from 100 to 200 

 imllims. in length and 10 millims. in breadth, which had a scale 

 of millimetres etched upon it. The glass thread forming the ca- 

 pillary tube was scratched by a knife at its lower end and broken 

 off so that the bottom opening coincided with the zero-point 

 of the scale, and thus the height h could be determined in the 

 non-immersed part of the tube. This precaution was necessary 

 in those cases in which the meniscus of the common surface of 

 liquids o and u could not be observed by optical means. 



When the lower end of the glass thread, together with the scale, 

 was immersed in the liquid u, without the caoutchouc rings 

 coming into contact with the liquid, and the upper closed end of 

 the capillary tube broken off, then the liquid o rose in the tube, 

 the liquid u followed, and h and h u could be read off with a ho- 

 rizontal telescope on the vertical scale. 



After that the fine glass tube was cut through in the place of 

 the upper meniscus, and the inner diameter 2r of the sectional 

 surface determined (in the way described in § 4) with a micro- 

 scope and an ocular micrometer. I did not determine the dia- 



* Young's Works, vol. i. p. 463 (1855). Encycl. Brit. " Cohesion," 

 sect. 2(1816). 



