The wires used were of good commercial lead and well drawn.

The special difficulty in experimenting with lead is due to its softness, involving initial lack of uniformity in section, which is increased on stretching. That the variability of the section of the wire might be allowed for in the computation of specific resistance, etc., the diameter was measured at the ends, at two points respectively one inch from each end, and at eight other points dividing the rest of the length of the wire into equal parts. The ends of the wire were soldered into copper pieces to prevent serious thinning near the ends when it was stretched.