ON A NEW VELOCITY RECORDER. 287 



this scale, the secondary changes of speed inside of each hour are 

 fairly indicated by the varying inclination of the strokes. The 

 driving shaft T S is placed vertically and coupled directly to a 

 Robinson's wind gauge by a vertical wire, which makes one 

 revolution to thirty of the cups. The wire may be of any length 

 so that the gauge may be on a pole on a tall building, and the 

 recorder under cover in the building below. As ordinary winds 

 seldom exceed thirty miles per hour, yet are stated to occasionally 

 exceed one hundred, the -pen gear is modified so as to give a 

 varying scale. Thus at to 5 m.p.h. the scale is about five miles 

 per inch, diminishing to half that between 20 and 30 m.p.h., and 

 so on, the extreme motion being to record 100 m.p.h. By this 

 device ordinary winds are recorded on a very open scale, and yet 

 exceptional gales can be included in a band of the moderate width 

 of five inches. This is accomplished by separating the pen-lever OM 

 from the sector N, and coupling them by a link* the relative 

 centres being so arranged that the angular velocity ratio changes 

 continuously and evenly from about two to one at 1 m.p.h., to 

 equality at about 25 m.p.h. and vanishing at 100 m.p.h. 



The diagrams from these instruments are difficult to reproduce 

 by printing, particularly those shaded diagrams produced by very 

 close ruling. Figs. 1 to 4 illustrate some records produced with 

 fairly wide time scales. 



Fig. 1 (a and b) are modified records of the velocity imparted to 

 -a Morse telegraph ribbon by a clock mainspring, a when controlled 

 by a Siemen's frictional governor, and b when controlled by a 

 plain rectangular fan or fly (1 *3" x -85"). In the former case a the 

 speed of the roller over which the ribbon runs commences at 

 about sixty revolutions per minute and steadily falls to zero, the 

 whole run lasting only about seventeen and a half minutes. With 

 the frictional governor the period of one unwinding of the spring 

 is extended to forty-five minutes, and the roller speed is fairly 



* See Eankine— " Machinery and Millwork/' page 312, article 273. 



