EXPERIMENTAL RESEARCHES ON DRAWN STEEL. 
27 
apparatus would allow, and the results in the table subjoined are the mean values 
of the experiments, which, however, differed very little among themselves. The 
principal source of error lay in the measurement of the diameters of the wires, for 
in one or two cases the wires appeared to be conical in shape, and in two cases were 
slightly elliptical in cross-section. By measuring the diameter at many places along 
the length of the wires, and confirming the results by calculation of the diameter 
from determinations of the density, the average sectional area has been arrived at. 
The numerical results are given in the third column of Table IX.,and in Diagram VII.; 
Diagram VI1. 
they are 2 >lotted as a curve, the sectional areas of the wires, which may he taken as a 
scale of traction, being treated as abscissae. There is a small I'eduction of diameter 
on annealing and tempering which is due not to traction, hut presumaljly to the j^i’O- 
duction of a little oxidation, which would be rubbed off afterwards wlien tlie wire 
was cleaned. 
The effects of annealing or tempering upon the resistivity come out in the curve 
* The diameters of the wires are given in Tables IT and III., and are not repeated in Table IX. 
E 2 
