147 
philosophy, was rejected — hut this abstract is already longer 
than usually allowed. 
“On the Electrical Resistance and its relation to the 
Tensile Strain and other mechanical properties of Iron and 
Steel Wire/’ by William H. Johnson, B.Sc. 
It has long been known that there is a great variation in 
the tensile strain of various qualities of iron and steel wire, 
depending on the mode of manufacture and purity of the 
material used, and it occurred to the writer that it would 
be interesting to examine if this difference in quality was 
accompanied by a corresponding alteration in the electrical 
resistance. 
If electricity is a mode of motion of the particles of 
matter, then, it is only reasonable to suppose that anything 
which constrains this motion will increase the electric resis- 
tance and vice versa. Thus an annealed wire should conduct 
electricity better than an 'i^^^iannealed and a hardened and 
tempered steel wire, whose particles are in a state of tension 
worse than a bright wire ; also from the analogy of copper 
wire any increase of impurities in the iron would probably 
augment the electrical resistance. The following experiments 
will be found to confirm these views. 
A series of preliminary experiments were made, beginning 
with a pure iron, smelted and worked throughout with 
charcoal and ending with a highly carbonized steel wire. 
The apparatus used was a Wheatstone bridge, with 
divided meter scale and reflecting galvanometer of low resis- 
tance. All the wires except the piano steel were drawn in 
the same way to No. 18J and then either hardened and tem- 
pered, or annealed and finished by drawing one hole to 
No. 20 = ‘038 inch. The length of wire tested electrically, 
varied from 8 to 3 meters ; care was taken to select such a 
length that the resistance was about I’Ohm., as then all four 
arms of the balance were equal. A thermometer was placed 
