56 Prof. W. C. Unwin. [Nov. 18, 



a solution of sugar in water. Lastly, a series of experiments were 

 made with water at different temperatures. Altogether several 

 hundred observations of the resistance of the disks under different 

 conditions were recorded. 



The figure shows a section of the apparatus employed. DD is the disk, 

 the friction of which, when rotated in fluid, is to be measured. This 

 is keyed on a shaft, SS, which was driven from a hot-air engine by 

 means of a catgut belt. The disk is placed in a cast-iron cistern, CC, 



