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of brass, 5, is soldered in a hole in the center. In this short cylinder the 
central rod system, which can be made of two or more sections, is insulated 
by pouring melted sulphur into the cylinder while the rod is supported in 
proper position by a cork, Fig. 3, which extends a short distance into the 
cylinder. After a few hours the cork can be removed, leaving the sulphur 
plug. In melting the sulphur care must be used not to get the sulphur too 
110 Vt 
Fie, 5. 
hot or to burn it. The melted sulphur should be a clear amber liquid. If 
the sulphur takes the waxy condition it should be discarded. The leaf is 
attached to a narrow plate which is attached to the lower end of the rod. 
The leaf which is a narrow strip of Dutch foil should be attached to the plate 
so as to be straight and to swing freely bending at a point near the plate. 
The deflection of the leaf is observed through a small window at one 
