New York Weather Bureau. 421 



rate of one turn in 6 minutes. Its contact piece is in circuit with 

 one pole of an electric battery, the other pole being grounded; and 

 the contact piece of (a) is also grounded throiugh the wind-vane 

 axis. Hence, when the contact piece of (b), in its steady rotation, 

 passes lOver the quadrant corresponding to that upon which the 

 wind-vane contact is resting, a current is allowed to pass through 

 (b) and i s connecting wire to (a) and thence to the ground. This 

 current ictuates an electro-magnet in the register, thus pressing 

 a pen agains' the cylinder until its contact piece, by rotation, 

 passes off from the quadrant corresponding to the wind direction, 

 when it is released. The pen falls vertically the length of the 

 cylinder once in 24 homrs, and, in the manner explained above, 

 at every revolution of the cylinder, leaves a trace upon that part 

 of its circumference which corresponds to the direction of the wind 

 at the time. 



The register, as thus described, records the wind direction only 

 to four points; but by broadening the contact piece of (a) so that 

 it can bear upon portions of two quadrants at the same time,, as, 

 for example, upon the north and west quadrants, for a northwest 

 wind, both north and west are recorded upon the cylinder, and 

 such a tracing is read northwest. 



As previously stated, the wires of the velocity register pass 

 through the hollow axis of the vane; and at the lower extremity 

 of the latter are connected through mercui'y cups with wires run- 

 ning to the Engineering building. At every hundredth revolution 

 of the anemometer, corresponding to 100 meters of wind, a circuit 

 is made through an electro-magnet of the register; and this turns 

 the proper recording cylinder through one one-thousandth part of 

 a complete revolution. The recording pen (which is attached to 

 the same carriage with that of the direction register), traverses 

 the length of the cylinder in 24 hours, and thus leaves upon the 

 tracing sheet a spiral line, every complete turn indicating 100 

 kilometers of wind. 



In addition to the hundredth meter contact, the anemometer is 

 also provided with a second contact, which is made at every revo- 



