TERRESTRIAL REFRACTION. 23 



the spout of a tea-kettle, was applied to one of them; 

 when it moved, from left to right, with violent con- 

 vulsive motions, (so rapid as hardly to admit of 

 counting them) 6 revolutions ; the 2d, 6 ; and the 

 3d, 6i ; when they remained quiescent. 



Now, we have seen above (exp. IV.) that a stem, 



of this length, and number of twists, revolved in that 

 n. ^ R. 



case 6+300°; and, in the present, nearly 6+180 (on 

 a mean of three). The application of steam, there- 

 fore, if we consider the small difference of the two 

 results, may be conceived to have affected the stem, 

 only in as much as it moistened it. 



Several other experiments were also tried, but be- 

 ing of the same nature as the foregoing, and the re- 

 sults nearly similar, they need not be particular- 

 ized. 



€4 



