OF CRYSTALS AND OTHER BAD CONDUCTORS. 
509 
On account of the low conductivity of paraffin, standard resistance coils with 
temperature coefficients ought not to be embedded in paraffin, as the B.A. standard is. 
Cork is the worst conductor experimented on. 
Almost all the substances experimented on are insulators electrically. Although 
tables of their electrical conductivities are available, the values given seem to depend 
more on the condition of the surface of the body experimented on than on its material, 
and, on this account, it is of little use to make any comparisons between the electrical 
and the thermal conductivities of these substances. 
The above experiments were carried on in the Physical Laboratory of the Owens 
College. 
