The plate in all cases projects over the edges of the test piece, and in no case should the length of the latter be less than four times the width of the plate.
_Measuring the deformation_: The compression is measured by means of a deflectometer (see Fig.

35), which, after the first increment of load is applied, is adjusted (by means of a small set screw) to read zero.

The actual downward motion of the movable head (corresponding to the compression of the specimen) is multiplied ten times on the scale from which the readings are made.
_Log of the test_: The load is applied continuously and at uniform speed (see SPEED OF TESTING MACHINE, above), until well beyond the elastic limit.

The compression readings are taken at regular load increments and entered on the cross-section paper in the usual way.

Usually there is no real maximum load in this case, as the strength continually increases as the fibres are crushed more compactly together.
_Calculating the results_: Ordinarily only the fibre stress at the elastic limit (c) is computed.