i?2 PLEAS A N7 WATS IN SCIENCE. 



ing to the astronomer, about which 1 must say a fev words . 

 I mean, the employment of electricity as a regulator of time. 

 Here again it is the principle of the system, rather than 

 details of construction, which I propose to describe. Sup- 

 pose we have a clock not only of excellent construction, 

 but under astronomical surveillance, so that when it is a 

 second or so in error it is set right again by the stars. Let 

 the pendulum of this clock beat seconds ; and at each beat 

 let a galvanic current be made and broken. This may be 

 done in many ways thus the pendulum may at each swing 

 tilt up a very light metallic hammer, which forms part of 

 the circuit when down ; or the end of the pendulum may 

 be covered with some non-conducting substance which 

 comes at each swing between two metallic springs in very 

 light contact, separating them and so breaking circuit; or 

 in many other ways the circuit may be broken. When the 

 circuit is made, let the current travel along a wire which 

 passes through a number of stations near or remote, travers- 

 ing at each the coils of a temporary magnet Then, at 

 each swing of the pendulum of the regulating clock, each 

 magnet is magnetized and demagnetized. Thus each, once 

 in a second, draws to itself, and then releases its armature, 

 which is thereupon pulled back by a spring. Let the arm- 

 ature, when drawn to the magnet, move a lever by which 

 one tooth of a wheel is carried forward Then the wheel 

 is turned at the rate of one tooth per second. This wheel 

 communicates motion to others in the usual way. In fact, 

 we have at each station a clock driven, not by a weight 

 or spring and with a pendulum which allows one tooth of 

 an escapement wheel to pass at each swing, but by the 

 distant regulating clock which turns a driving wheel at the 

 rate of one tooth per second, that is, one tooth for each 

 swing of the regulating clock's pendulum. Each clock, 

 then, keeps perfect time with the regulating clock. In 

 astronomy, where it is often of the utmost importance to 

 secure perfect synchronism of observation, or the power of 

 noting the exact difference of time between observations 



