were a new set obtained from Mr. Bown. I also had from him one ball of
each of each of the following sizes 3, 4, 5, 6, and 7 16ths of an inch
in diameter, as I was curious to know what weight they would suppport
without crushing. As as preliminary experiment, I placed a spare 5/16
ball between the crushing faces of the new testing machine at South
Kensington, and applied a gradually increasing force up to 7 tons 91/2
cwt., at which it showed no signs of distress. On removing it I found
that it had buried itself over an angle of about 60 deg. in the hard steel
faces, faces so hard that a file would not touch them. Those marks will
be a permanent record of the stuff of which the ball was made. The ball
itself is sealed in a tube, so that any one who is curious to see it can
do so. Finding that the crushing faces were not sufficiently hard, I
made two anvils of the best tool steel, and very carefully hardened
them. These, though they were impressed slightly, were sufficiently good
for the purpose. In the following table are the results of the crushing
experiments:

3/16 ball at 2 tons 13 cwt. did not break, but crushed on removing part
of the weight.

1/4 ball at 3 tons 15 cwt. did not break, but crushed on removing part of
the weight.

5/16 ball at 4 tons 9 cwt. broke.

3/8 ball at 8 tons 6 cwt. did not break, crushed under another 120 lb.

7/16 ball crushed before 3 tons, with which I was starting, had been
applied. Examination showed that the steel bar of which it was made had
been laminated.