aK 
a 
7 
of Magnetical and Meteorological Instruments. 325 
wide, and a quarter of an inch in thickness: it is suspended with 
the broad side vertical, in a brass stirrup carrying a divided circle 
(a) by which the position of detorsion of the thread is made to 
coincide with the meridian, and two keepers (4, b) capable of 
of about sixteen inches focus; it can be set to any required height 
on the stem (d) and be made to form any required angle with 
the axis of the magnet. The whole suspended weight amounts 
bly in different hygrometric states of the atmosphere, thereby disturbing the adjust- 
ment of light sufficiently in some cases to make it ineffective. fine metallic 
Suspension, as was originally used by M. Gauss, for his declinometer, if very long, 
Would probably be preferable to silk. 
