Prime meridian

June, 1879.]

Prime Meridian.

417

Reversal of M o t i o n W i t h o u t . G e a r s or Belts.--In 1853, MM. Claparade, Roux and Delille attempted to produce opposite revolutions in two parallel arbors by means of a Watts parallelogram, but these experiments were not satisfactory. Charles Bourdon has lately intro