

ARTICLES 227 



of their results, with carbon disulphide as the liquid and 

 r =0-0129 cm., they obtained : 



At / = 19-4° C. at / =46-i°C. 



,, h = 4'2i cm. „ h = 3-80 cm. 



h = 4-20 cm. ,, h = 3*795 cm. 



h = 4-20 cm. ,, h = 3'8o cm. 



mean h = 4-203 cm. mean h = 3798 cm. 



,, d ^ 1-264 cm. ,, d = I "223 cm. 



T = i grdh. 



T = 33-6 dynes per sq. cm. Ta = 29-4 dynes per sq. cm. 



They then used these values to calculate dT (MvY 



dt, 

 Ti {Mldi)i = 33-6 (76/1 -264)* = 515 ergs. 

 r, (A/"/(f,)« = 29-4 (76/1-223)5= 461 ergs. 



then *i^' = 5-5 " 46i ^ ^ ^ ,.„,. 

 at 46-1 — 19-4 26*7 



The defect of the apparatus consists in the fact that the outer 

 tube is not sufficiently wide to ensure that there is no capillary 

 rise there, thus making the result too low. More theoretically 

 perfect is the apparatus used by Richards and Coombs. The 

 capillaries were carefully selected according to the method al- 

 ready described : in one form the diameters of the narrow and 

 wide tubes were 0-20198 and 3-8 cm. respectively, and in the 

 second 0-01936 and 3-8 cm. ; the volume of liquid required for the 

 first tube was 36 c.c, but this was reduced to 12 c.c. in another 

 form by means of the sinker. A reference mark was etched 

 near the centre of the capillary. Particular care should be 

 taken, when using apparatus containing stopcocks, to make 

 certain that these are thoroughly clean ; they can only be 

 lubricated with the liquid in the tube, and, so as to prevent the 

 entrance of water, the outside of the tap is covered with a film 

 of paraffin before the apparatus is placed in the bath. The 

 method used to observe the position of the meniscus with accu- 

 racy was to set the apparatus vertical with a plumb-line in the 

 thermostat (which had parallel plate-glass sides). A black 

 metal screen having a rectangular hole in it, with the horizontal 

 edge quite straight, was lowered into the thermostat so as to 

 lie just behind the apparatus, and was then adjusted so that the 

 straight edge was just horizontal, and when viewed through the 

 cathetometer, appeared to make a tangent with the lowest point 

 of the meniscus. The upper edge of the meniscus could also 

 be determined when desired by gradually raising the plate, 

 whereby the line of the straight edge at first appears broken, 



