1886.] Magnetisation in the Length of Iron Wires. 



259 



an axial hole drilled through it, which is tapped to receive a screwed 

 brass rod terminating in a stirrup S. The bottom of the stirrup is 

 formed like a knife-edge with the edge uppermost, and beneath it is 

 fixed a hook H, from which weights may be suspended. A second 

 perforated stopper B is fitted to the upper end of the tube ; the hole 

 through this is left smooth and freely admits a brass rod, which is 

 suspended by means of a pin at P from a thick brass plate attached to 

 the mahogany table T. The height of P can be varied within small 

 limits by means of a fine screw adjustment, not shown. The table T 

 is attached to the base-board F of the instrument by three stout legs, 

 only one of which, L, appears in the diagram. The wire under ex- 

 periment, X, is clamped at its two ends between slits in the ends of the 

 brass rods P and S, and thus supports the coil in an upright position. 

 By turning the screwed plug A the position of the wire X may be so 

 adjusted that its middle point shall coincide with that of the axis of 

 the coil.* The knife-edge of the stirrup acts upon the brass lever R, 

 one end of which abuts upon a fixed fulcrum D, while the other 



* Exact coincidence is not essential. 



