in Free, Surfaces of Liquids 



145 



a peculiarity of homogeneous liquids, free from any foreign 

 mixture, or whether substances coming from the atmosphere 

 or from the sides of the vessel into the free surface cooperate. 

 As water and salt-solutions generally possess but little different 

 and proportionally high capillary-constants*, the possibility 

 is given of an outspreading of substances possessing less 

 tension. 



The investigation of free water-surfaces which, not only 

 during the experiments, but also previously, have been pro- 

 tected from all contact with the air might be extraordinarily 

 difficult; at all events the arrangements necessary for it were 

 wanting to me. 



The precautions employed by me — filtering the water 

 (heated to boiling) into a narrow-necked flask, covering the 

 glass vessel during the experiment with wet filtering-paper — 

 had almost no influence at all upon the numerical values ob- 

 obtained. Also water from the conduit did not show any 

 essential difference from distilled water. I tried still another 

 means in order to ascertain the action of the contact of the air 

 or of the particles suspended in it. If that is the chief reason 

 for the peculiar behaviour of the water, the action must in- 

 crease with the time which has elapsed since the free surface 

 was formed. Respecting this I made the following experi- 

 ments. As quickly as possible after pouring the liquid into 

 the vessel the state of the free surface was examined; after a 

 longer time the examination was repeated. Finally it was 

 attempted by mechanical means (stirring with a clean plati- 

 num plate, shortly before heated to incandescence) to remove 

 foreign bodies from the surface. Some of these experiments 

 are collected in the following table. The numbers given are, 



as before, the quotients ^ The brass plate, as well as the 



brass cylinder, were placed so that their upper extremity 

 exactly touched the free surface. 



Table VI. 



Eectangular plate : 



Rectangular plate : 



Cylinder : distance 



distance betwen the 



distance between the 



between the sides 



sides 20 mm. 



sides 15 mm. 



15 mm. 



h. m. 





h. m. 





h. m. 





1 20 



2045 



11 7 



2649 



9 30 



3388 



2 45 



2132 



12 5 



2744 



10 45 



3360 



After stirring 



1909 



After 24 hours 

 Stirred 



00 



2539 



Stirred 



3374 



* Quincke, Pogg. Ann. clx. p. 337-375, 560-588 (1877). 

 Phil. Mag. S. 5. Vol. 11. No. 66. Feb. 1881. L 



