166 



Professor TyndalPs further Researches 



are connected by a brass cross-piece, in which is the point of 

 suspension P ; and the position of the helices is shown to be 

 between the magnets. It will be seen that the astatic system is 

 a horizontal one, and not vertical, as in the ordinary galvano- 

 meter. The black circle in front of the magnet SN, fig. 2, is a 

 mirror, which is shown in section at M, fig. 4 ; to balance the 

 weight of this mirror, and adjust the magnets in a horizontal posi- 



Fig.l. 



Fig. 2. 



Fig. 3. 



I4|jM|^ I 



il 



Fig. 4. 



w 





iS' 



13^ 



tion, a brass washer, W, is caused to move along a screw, until a 

 point is attained at which its weight has brought both the magnets 

 into the same horizontal plane. There is also another adjustment, 

 which permits of the magnets being brought closer together or 

 separated more widely asunder. The motions of the compound 



