310 A. M. Mayer on measuring Electrical Conductivities. 
ped; which would have taken place if it had been coiled 
in the direction from d to A. Th 
taken off the chuck, and on holding it up to the light the 
copper wire is distinctly seen through the translucent covering 
of the wire and the paraffined paper cover of the spiral. The in- 
sulation thus obtained is very perfect and the coils are firmly 
cemented together. The terminals are now led radially from 
the spirals, and are tightly bound together as described above. 
To still further strengthen the spirals, both they and their ter- 
minals are covered with a firm layer of shellac varnish. 
I have thus minutely described the process of making these 
spirals for they are of inestimable value in many electrical 
researches ; having been used in my recent investigations in 
electro-magnetism, and will be again used and referred to in a 
n this position the magnet caused a deflection of 52/5 in the 
needles of the galvanometer and they were brought back into 
the meridian by means of the damping-magnet. 
The deflections of the needles were read off by the beautiful 
