347 



was liiglily facilitated, by putting a half transparent and dilFusel}' 

 illuminated screen behind the inanometertube, on which screen black 

 lines were drawn under an inclination of about 25° with the horizon 

 in snch a way, that their mirror-images in the mercury-suj'faces 

 were visible thereupon as a bundle of very line and easily discern- 

 ible dark lines. After the application of a certain excessive pressure 

 to both manometers, two observei-s read simultaneously both instru- 

 ments ; the manometers were connected with each other by a short, 

 very wide tube, sufficiently protected against temperature-oscillations. 

 As an example of this calibration, the following series of obser- 

 vations may be i-eproduced here in detail : 



A rise of the octane over 1 m.m. is therefore equivalent to an 

 excessive pressure of 0,0561 + 0,0003 m.m. mercury (=174,8^0,4 

 Dynes). 



After it was found, that our measurements of the free surface- 

 energy of purest water, were in so complete agreement with those of 

 VoLKMANN, Brunner, Worlev, amoug others, we afterwards repeated 

 this calibration in most cases by the accurate determination of x lor 

 pure water, at three or more temperatures. The factor of enlargement 

 F of the manometer appeared after all to be only slowly variable : 

 in Octobre 1913 e.g. it was: 17,91 in February 1914: 17,86; in 

 June 1914 : 18,10; etc. 



§ 12. The molten salts to be studied were in most cases placed 

 into crucibles of iridium-free platinum ; for the organic liquids we 

 used vessels of glass of the shape indicated in fig. 7. A cylindrical 

 glass tube P with rounded bottom possesses a narrower neck at 

 A; a wider glass cup A is fixed round it. A tube G, closed with 

 a stopper K, which is firmly fixed round the platinum capillary tube, 

 possesses a collateral tube B, which ends into a drying tube G, which 

 communicates with the free atmosphere at Z, and which is filled with 



