272 Prof. G. Quincke on the Capillary 



common surface in such a manner that the capillary tension on 

 them is constant and attains the maximum value which is pos- 

 sible for the common limiting surface of the two bodies. 



If this arrangement be changed, by the force of crystalliza- 

 tion for instance, the fibrous structure changes into a crystal- 

 line one, and the solidity must become much smaller. 



In drawing wire, hollow cylinders of metal of differing density 

 glide over each other. The heat developed by the drawing con- 

 tributes to render the metal particles more readily displaced, so 

 that on the common surface of two such hollow cylinders the 

 capillary tension is a maximum. The tenacity of hard-drawn 

 wires must be greater than that of annealed ones. In physical 

 mixtures of heterogeneous substances (alloys, steel) wire-drawing 

 must favour the formation of capillary surfaces more even than 

 in the case of homogeneous metals ; so that in these the decrease 

 of the capillarity- constant is most marked. All this agrees with 

 observation. 



The great tenacity of bodies which are built up of thin systems of 

 tubes, like bones, the tenacity of organic substances which consist 

 of individual cells with large capillary surface, are explained by this 

 capillary tension. If these solids have been originally formed 

 from soft masses, on their solidifying there has been a constant 

 tension in the entire capillary surface as great as was possible 

 under the given circumstances. The changes which this tension 

 of the surface subsequently undergoes in consequence of altera- 

 tions in temperature or of the form of the surface, will in general 

 be small in comparison with the whole value on solidification. 



The alteration in the measures used for geodetic purposes, 

 which have recently been demonstrated by M. Bseyer*, may 

 partially arise from the usual prismatic form, which agrees so 

 little with a surface of equilibrium. In spheres, solid as well 

 as hollow, there is little reason to apprehend changes of this kind. 



The difficulty of assuming forces near the surface of solids 

 which depend on the form of the surface, in opposition to tradi- 

 tional ideas, is not in fact so great as might at first sight appear. 

 Displacements of the molecules of what are called solids have 

 long been known. The plasticity of icef, the phenomena of re- 

 gelation J, the experiments of M. Tresca on the efflux of solids §, 

 the different deportment of the same substance according as it is 

 in the crystalline or the colloid condition, indicate a more or 

 less prominent community of properties in solids and liquids. 



A rigidly theoretical treatment of the capillary phenomena of 

 solids is rendered more difficult by the circumstance that the 



* Berliner Monatsberichte, 186/, p. 1. 



t Forbes, Phil. Trans. 1846, p. 143. Tvndall, Phil. Trans. 1857, p. 327. 



t Faraday, Phil. Mag. vol. xvii. p. 162 (185.9) , vol.xxi. p. 146. 



§ Comptes Rendus, vol. lix. p. 754 (1864) ; vol. lx. pp. 398 & 1226 (1865). 



