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FiG. 319.

Fio. 319. A brass block (enlarged) in which the seven instrument points have been struck, all
with the two-tenths pound mallet, falling 33.56 inches. The prosjressive increase in depth reading fron\
the larger to the smaller is only moderately well shown. The depth is .14 millimeters for the largest
instrument, increasing to 1.25 millimeters for the smallest.