•24 MR. BROOKE ON THE AUTOMATIC REGISTRATION OF MAGNETOMETERS. 
Description of the Plate. 
Figs. 1 and 2. Plan and elevation of the bifilar compensator, half the actual size, a a 
the magnet, h the clamp which attaches the glass rod to the magnet, c c the 
zinc tubes enclosing the glass rod. dd the adjusting clamps, consisting of 
two parts ; the outer encircles the zinc tube, the inner passes, and nearly fills 
the interval, between the tube and glass rod. They are capable of sliding for 
adjustment when the screws are loosened ; when tightened, the rod and 
tubes are held together, ee screws for adjusting the distance between the 
hooks /i// ; these should be withdrawn, when the clamps d are fixed, oo, 
fig. 2, are the ends of the clamping pieces interposed between the tubes and 
the rod. 
Fig. 3. The brass collar to which the hook is attached seen in section, full size. The 
glass rod f rests on a roller g, that there may be no jerking in the expan- 
sion and contraction of the tube ; ii two screws for fixing the collar while 
the scale and temperature coefficients are determined ; when these are 
tightened the clamps d and screws e should be relaxed. 
Fig. 4. Plan of the balanced magnet compensator, kk the magnet. 1 1 the thermo- 
meter tube held in two Ys by a spring m tightened by a screw, nn the 
clamp that attaches the magnet to the frame in which the agate knife- 
edges are fixed. 
