112 Captain Kater on the best kind of steel 
Experiment g. 
Needles soft, and then the ends hardened 
Directive 
at a red heat. 
force. 
Small rhombus 
477 
Large rhombus - 
4h5 
Pierced rhombus 
450 
Here we may remark, that though the needles were appar- 
ently in the same state, except being re-carbonized, as in the 
last experiment, they had suffered considerable deterioration. 
The needles were now covered with a mixture well known 
to workmen to prevent decarbonization : this had been before 
neglected, but was used in all the subsequent experiments. 
They were hardened at a bright red heat, and afterwards 
tempered throughout rather beyond a blue colour. The large 
rhombus and the parallelogram were accidentally broken. 
Experiment 10 
Hardened at a blight red, and then tem- 
Directive 
pered beyond a blue. 
force. 
Small rhombus 
660 
Pierced rhombus 
£77 
From these last experiments I believe little can be ga- 
thered, except that the needles became less susceptible of 
directive force from repeated exposure to heat, and that this 
effect was not occasioned by a decarbonization of the steel. 
The small rhombus of saw blade, perhaps, from being the 
thickest, suffered less than those made of clock-spring. 
