94 Prof. G. Quincke on the Constants of 



a fine point was inserted air-tight in the cork. When the bottle 

 was inverted, after the water had cooled down with the access of 

 the external air shut off, this point lay in the water immediately 

 below the lowest part of the upper surface of the fluid. The 

 meniscus was formed on a part of the glass wall which had 

 previously remained wet, and was observed with the microscope 

 of the cathetometer which I previously described*. One or two 

 seconds after the formation of the meniscus, the cross threads of 

 the microscope were directed upon its upper limiting surface. 

 This surface, lighted up from behind by a paper half white, half 

 black, so that the horizontal limit of the black and white lay at the 

 same height with it, appeared as a well-defined dark line. The 

 point lying in the water was mirrored in the water-surface 

 bounded by the space free from air. The cross threads were 

 set in the middle between the point and its image, and so the 

 position of the horizontal part of the fluid surface was determined. 

 The point seen through the water distinctly in the microscope 

 appeared in the middle of the bottle, while the wall of the me- 

 niscus was first seen distinctly sideways from the middle of the 

 bottle ; between the two determinations the microscope had there- 

 fore to be shifted on the plate of the cathetometer, which was 

 made accurately horizontal by a spirit-level. 



Previously to this boiling, the bottles as they came from the 

 glass-blower were purified partly with water and alcohol, partly 

 with hot concentrated sulphuric acid, and were then filled with 

 distilled water and allowed to stand aside for some hours. The 

 water used for the experiments was put in a little before the 

 boiling. The measurements were made as soon after the turning 

 upside down of the bottle as possible, as the elevation diminishes, 

 at first rapidly and then gradually, immediately after the formation 

 of the capillary meniscus. 



I may give here a series of determinations for different bottles 

 the diameters of which arc denoted by D, from which we may 

 infer the accuracy which it is possible to secure in such deter- 

 minations. 



US. 



11. 



III. 



IV. 



millims. 



millims. 



millims. 



millims. 



D = 52-7 



5.2-05 



50-3 



50-3 



Temp. 17°'l C. 



17°-5 



17° 



(17°?) 



millims. 



millims. 



millims. 



millims. 



1-015 



4-072 



4-00 L 



4-207 



4-176 



4-015 



4-105 



4-164 



4-110 



3-993 



4-180 



4-110 



4-155 



3-900 



4-160 



4-166 



.... 



.... 



4-146 



.... 



can . 4*114 



3-995 



4-119 



4161 



* Pogg. 



Ann. vol. cv 



p. 12(1858) 



. 



