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A bone crusher was a device for crushing animal bones. Bones obtained during slaughter were cleaned, boiled in water and dried for several months. After that, they were suitable for crushing with the special machine into a relatively dry gritty powder which was used as fertilizer.
The machine, shown in the picture, is powered by a water wheel. It contains eight S-shaped pairs of cams that raise the crushers alternately and let them fall into material to be crushed. The simple transmission increases the rotation speed of the crusher wheel to 21 rpm from the water wheel speed of about 7 rpm.
Bone meal was used since about 1790 as a welcome supplement to the ordinary farmyard manure. From about 1880 it was supplanted by chemical fertilizers.
Similar machines
A similar machine (the stamp mill) is used to crush ore in mining situations.