391. Reciprocating into rotary motion. The weighted racks, A, A1, are pivoted to the end of a piston-rod, and pins at the end of the said racks work in fixed guide-grooves, b, b, in such manner that one rack operates upon the cog-wheel in ascending and the other in descending, and so continuous rotary motion is produced. The elbow lever, C, and spring, d, are for carrying the pin of the right-hand rack over the upper angle in its guide-groove, b.