Page:Popular Science Monthly Volume 53.djvu/333

Rh of the wind vane and is provided with four cams, each of which extends over three eighths of the circumference and the central points of which are a quarter of a circle apart. Four contact levers, having rollers in their ends, hear on these cams; and, when raised



by the cams, the levers touch contact springs having a wire from each that runs to one of four magnets beside the "triple register." The levers and magnets are all connected with batteries. The magnets act on armatures that are carried by levers, one for each magnet, which have pens that make a dot on the paper of the cylinder every time the magnet acts. One or two contact levers are always elevated by the cams to make a contact. The cams are so arranged that only one cam acts when the vane is directed to a cardinal point of the compass; but, when it is between two such points, two of the cams are acting. Thus the eight principal directions of the wind are indicated by the four pens. The clock breaks the circuit of the vane except for an instant each minute, so that the pen in action makes a dot each minute.

The velocity of the wind is registered by an instrument consisting of a vertical shaft which carries four horizontal arms having sheet-metal cups on their ends. The wind acts more strongly on the open faces than on the backs of these cups, and causes them to revolve the shaft. Through gearing connected with the shaft, pins on an index close an electric circuit for every mile the wind travels, and the current through a magnet of the triple register causes a sidewise