The hoisting-mechanism is all controlled by a single operating lever, shown on the side of the column, whereby the striking weight may be raised, lowered, or stopped at the will of the operator.

There is an automatic safety device for stopping the machine when the weight reaches the top.
[Footnote 59: For description of U.S.Forest Service automatic and autographic impact testing machine, see Proc.Am.Soc.

for Testing Materials, Vol.

VIII, 1908, pp.

538-540.] [Illustration: FIG.