402 



Mr. T. Proctor Hall on New Methods of 



dust &c. are more easily seen, but it requires careful washing 

 with a soft brush. 



Under favourable conditions — a fresh clean surface, con- 

 stant temperature, no dust, no disturbing vapours — a high 

 degree of accuracy is attainable by this method. The fol- 

 lowing are selected from my results when these conditions 

 were most nearly fulfilled. 



1. Platinum plate, 13*495 centim. long, '0045 centim. thick, 

 in 99'8 per cent, alcohol. Error of setting, calculated, 

 •02 dyne. 



w. 



T (dynes). 



Temp. 



•6210 



22-548 



18-22 



•62095 



22-543 



18-25 



•6209 



22-537 



18-29 



•6209 



22-537 



18-31 



The temperature-correction for 0°'l is — *008 dyne. 



2. Mica plate, H'3180 centim. long, *0007 centim. thick, 

 in common alcohol at 17 o, 20 0. 

 •003 dyne. 



Calculated error of setting, 



w. 



T (dynes). 



•55301 

 •55307 

 •55306 



23-949 

 23950 

 23-950 



3. Mica plate, H'42285 centim. long, '0004 centim. thick, 

 in common alcohol. Calculated error of setting, *002 dyne. 



w. 



T (dynes). 



Temp. 



•56360 

 •56363 

 •56363 



24183 

 24-184 

 24-184 



16-20 

 16-24 

 16-26 



c. 



It has been already stated that, in order to form a true film 

 between the liquid and the bar m of the frame (fig. 1), this 

 bar must be from five to ten millimetres above the level 

 surface. Even when the bar is excessively thin a distinct 



