Observations on Tron and Steel. 121 
the steel be too hot when immersed in water, the 
grain will be of a rough and coarse texture; but 
if of a proper degree of heat, it will be perfectly 
fine. Saws and some other articles are quenched 
in oil. | 
Steel is tempered by again subjecting it to the 
action of the fire. _ The instrument to be tempered 
we will suppose to be a razor made of cast steel. 
First rub it upon a grit stone until it is bright; then 
put the back upon the fire, and in a short time the 
edge will become of a light straw colour, whilst the 
back is blue.‘ The straw colour denotes a proper 
temper either for a razor, graver, or penknife, 
Spring knives require a dark brown; Scissars, a 
light brown, or straw, colour 3 forks or table knives, 
a blue. The blue colour marks the proper temper 
for swords, watch-springs, or any thing requiring 
elasticity. The springs for penknives are covered 
over with oil before they are exposed to the fire to 
temper, 3 
VOL, Vv. 2 
