656 PLATEAU ON THE PH^ENOMENA OF A FREE LIQUID MASS 



The intensities of the configuring forces corresponding to dif- 

 ferent liquids may be compared numerically for the same curva- 

 tures. In fact, let us first bear in mind that the pressure cor- 

 responding to one element of the superficial layer and reduced 

 to unity of the surface, is expressed by (§ 4), 



Now, the value of the part P of this pressure being the same 

 for all the elements of the superficial layer, and the pressures 

 being transmitted throughout the mass, this part P will always 

 be destroyed, whether equilibrium exists in the liquid figure 

 or not ; so that the active part of the pressure, that which con- 

 stitutes the configuring force, will have for its measure simply 



— (-n+-ny ). Hence it is evident that when the curvatures are 



equal, the intensity of the configuring force arising from one ele- 

 ment of the superficial layer is proportional to the coefficient A. 

 Now this coefficient is the same as that which enters into the 

 known expression of the elevation or depression of a liquid in a 

 capillary tube, consequently the measures relating to this eleva- 

 tion or depression will give us, in the case of each liquid, the 

 value of the coefficient in question. Hence we may also say 

 that the proportion of the normal length of the divisions to the 

 diameter of the cylinder will be greater as the liquid is more 

 viscid and as the value of A which corresponds to the latter di- 

 minishes. For instance, oil is much more viscid than mercury ; 

 on the other hand, it would be easy to show that the value of A 

 is much less for the first than for the second of these two liquids ; 

 lastly, this value must be much diminished in regard to our 

 figure of oil by the presence of the surrounding alcoholic liquid, 

 the mutual attraction of the molecules of the two liquids in con- 

 tact diminishing the intensities of the pressures (§ 8). This is 

 why the proportion belonging to a cylinder of oil formed in the 

 alcoholic mixture considerably exceeds that belonging to a cylin- 

 der of mercury resting upon a plate of glass, notwithstanding 

 the slight external resistance to which the latter is subjected. 



60. It followi from this discussion concerning the resistances, 

 that the smallest value which the proportion of the normal length 

 of the divisions to the diameter of the cylinder could be sup- 

 posed to have, corresponds to that case in which there is simul- 

 taneously complete absence of external resistance and of vis- 



