the Laws of Magnetic Forces. 283 



long, and about half an inch in depth *. The magnet and scale 

 which pass through this opening rest in a corresponding band y 

 below ; this lower band being fixed to the brass plane. Each 

 band has two small screws, the milled heads of which are seen 

 projecting at V and y : these are to retain the magnet and scale 

 firmly in their place by slight pressure. When small magnets 

 are used, they are easily secured in their situation against the 

 scale my, by a slight pressure of the screw V. The magnet and 

 scale being fixed, we are enabled, by turning the head of the ver- 

 tical screw at S, to raise or depress them through any required 

 interval within the range of the screw, and so adjust the distance 

 between the upper pole of the magnet and the lower pole of the 

 suspended body x, with great accuracy. 



1 1 . Besides these means of adjustment, there are one or more 

 detached bands of brass, Fig. 3., somewhat similar to the fixed 

 bands already described, which are occasionally applied to any 

 part of the divided scale, so as to fix a magnet, or a mass of iron, at 

 any required distance from each other, as shewn in Figs. 5. & 12., 

 or otherwise allow of pressure being made about the centre of the 

 bar, as at H, Fig. 1., by which means it can be elevated on the 

 scale if necessary. These bands also serve to sustain a magnet 

 or a mass of iron in an horizontal position, as in Fig. 11., there 

 being two spaces, h h, Fig. 3., through the sides. 



12. When it is required to examine the force of a magnet in a 

 vertical position, it is placed in the situation just described (10.), 

 and then transferred immediately under the suspended body #, 

 there being a portion of the circular base B', Fig. 1 ., removed 



* The spaces are sufficiently large to receive one or more magnetic bars of a con- 

 venient size, the interval, when only one is employed, being filled up by a piece of 

 wood placed behind the scale, to keep it steady. The scale extends about three 

 inches above the magnet, and through its whole extent below : it can therefore be 

 raised between the magnet and wood to any further altitude required. 



VOL. XI. PART II. N n 



