Sentence:  He has considerably improved upon the planing machine, in his “<WSD>Jim Crow</WSD>” machine, so called because the cutter reverses itself and works both ways, and in fact adapts itself to any position to do its work. 
Meaning of the word marked with <WSD> tags:  A double-action planing tool invented by (Joseph Whitworth), in which the blade ‘jumps' to face the other way on the back-stroke.