For transverse tests, a well-rounded knife edge is screwed into the weight in place of the flat head.
Knife edges for supporting the ends of the specimen to be tested, are securely bolted to the base of the machine.
The record of the behavior of the specimen at time of impact is traced upon a revolving drum by a pencil fixed in the striking head.

(See Fig.

41.) When a drop is made the pencil comes in contact with the drum and is held in place by a spring.

The drum is revolved very slowly, either automatically or by hand.

The speed of the drum can be recorded by a pencil in the end of a tuning fork which gives a known number of vibrations per second.
[Illustration: FIG.