421 



§ 4. The rather a[)|)reciciltle ditlerences of our resulis with lesjiect 

 to the variations of ft and ■/ witli the temperature, with those of 

 other investigators, who have principally worked after the method 

 of capillary ascensions, have suggested to us to investigate in detail, if 

 perhaps in our way of working certain factors could be present, 

 which may cause systematical errors in any direction ? 



First it was noted, that besides the particular shape of the mentioned 

 curves, also the absolute values of /, determined by us and already 

 by Fecstel, were generally somewhat higher, than those obtained 

 with the same liquids by other experimenters and by other methods. 

 Of course it is very well possible, that e.g. the lower values published 

 by R\Ms.\Y and Shields, and obtained by them by means of the 

 method of capillary ascension, are caused by the fact, that the 

 moistening of the glass-walls in their capillary tubes has been not 

 so complete, as is supposed in the theory of the phenomenon. In that 

 case the angle of contact ff will play again a role ; and because the 

 height of ascension ceteris paribus is proportional to the cosinus of 

 the supplementary angle of 'f, there could thus really be found a 

 cause, which would make their results appear smal/er, than those 

 obtained in our work. 



But moreover we were able to prove on the other side, thai our 

 values for •/, calculated after Cantor's theory, must surely appear 

 somewhat higher, than they really are, because in praxi the 

 conditions are not completely fu Hilled, on which is based the 

 deduction of the final formula between H, di and r in Cantor's 

 theory. 



Let us start with the somewhat more summary deduction of his 

 formula by Feustei. ^). From this deduction as it is found in the 

 paper of this author, it can be seen, that the formula of Cantor 

 can have only validity in the special case that the angle <9, which 

 the tangent in every point of the sharp edge of the capillary tube 

 drawn in any azimuth to the rotation-surface of the small gasbubble, 

 makes with the horizontal surface of the liquid, — differs only slightly 

 from 90°; in that case 6* = 90° — ?,- wherein f has a very small 

 value. Some years ago prof. Lorentz was so kind as to draw my 

 attention to the fact, that this limiting supposition can be avoided, if 

 one makes a few simple substitutions in the two formulae of Feustel : 



2x ^ 1 



cos a = r . di. 



r (1 — cos Oy- 



and 



1) R. Feustel, Ann. d. Phys. loc. cit. 

 Proceedings Royal Acad. Amsterdam. Vol. XVII, 



