﻿374 M. G. Quincke on the Capillar]/ Phenomena 



vacuum, as I expressly observed at the time, contains vapours 

 of grease*. 



The condensation of vapour on the surface of mercury appears 

 to go on with tolerable rapidity; and in spaces containing vapour 

 of oil of turpentine, K and K— & are found to be unusually small. 

 In like manner the vapour of petroleum and even the grease 

 from the hair and body have considerable influence on the form of 

 the drops of mercury. 



Thus it may easily happen that liquid 3 may be placed on a 

 drop of mercury which is already coated with an extremely thin 

 layer of a liquid 4; then a will be 



Now, accordingly as this value is greater or less than a 13 + a 3 , a 

 may be found by observation greater or less than the theory of 

 § 11 requires. As the value a 13 + a 3 for mercury and water as 

 substances 1 and 3 of Table X. § 10 is very great, but for mer- 

 cury and oil of turpentine is very small, for water placed as sub- 

 stance 3 on~ the apparently pure surface of mercury a must be 

 found too small, and for oil of turpentine as substance 3 too 

 large. Besides, a 14 and a 43 depend on the greater or less thick- 

 nesses of the films of substance 4, which is often less than twice 

 the radius of the sphere of action, and is completely beyond ex- 

 amination, so that the difference between the observed and the 

 -calculated values must turn out sometimes greater and sometimes 

 less (compare § 27) . 



Experiment confirms all these conclusions, often in an unde- 

 sirable manner, as the form of a drop of mercury in air is often 

 changed by a trace of liquid which was by no means supposed 

 to be in the atmosphere. 



On placing petroleum upon flat drops of mercury I likewise 

 found in four experiments a always greater than the theory (ac- 

 cording to the determinations of Table X. for o* ]3 + a 3 ) had led 

 me to expect. 



The influence of the vapour adsorbed or condensed on the free 

 surface of the drops naturally manifests itself more plainly in air 

 than in the air-bubbles described in the experiments of § 12, 

 which are protected from impurities by the surrounding liquids. 



14. Instead of placing a liquid 3 on the free surface of a liquid 

 1 or 2 bounded by air, it may be placed on the common surface 

 of two liquids 1 and 2, which was presupposed as the most ge- 

 neral case in the theoretical considerations of § 11. 



On flat drops of olive-oil or bisulphide of carbon in water, 

 which were obtained according to the method described in § 7, 

 oil of turpentine was placed, and on flat drops of mercury in water 

 olive-oil, oil of turpentine, or petroleum was placed. 

 * Pogg. Ann. vol. cv. pp. 33, 43 (1858). 



