228 CIRCUMNUTATION. [CH. VIII 



movement. The head of the observer is moved until the 

 globule of sealing-wax is exactly in the centre of the 

 paper triangle, and a dot is made on the glass in line 



Fig. 43. Exp. 258. From Poiver of Movement. 



with these two points. The dot should be made with a 

 piece of hard wood cut to a sharp point like a pencil, and 

 dipped in Indian ink or moistened with water-colour. It 

 is best to hold the pointer as close as possible to the 

 glass until the observer has made up his mind where 



