44 J. H. Lane on an Automatic Comparison of Time. 
Secondly, a uniform automatic movement at A, made to inter- — 
rupt the light at regular minute periods of say one sixteenth ofa — 
second from the middle of one interruption to the middle of the — 
next. ‘ 
Thirdly, a uniform automatic movement at B, by which the — 
star of light is made optically to travel around a circle at the 
rate of one revolution in the same period of one sixteenth of a — 
second, the consequence of which is that the periodical inter: — 
ruption becomes visible to the eye as a break in the luminous 
circle produced by the motion of the star, and according as such _ 
break is seen upon one part or another of the circumference of 
the luminous circle, the relation of the movement at A to that 
A and B to each other, or of the quantity by which one may be 
in advance of the other in its motion. 
Fifthly, any of the known methods of effecting automatic com- 
Further, if the automatic movement at B, besides giving opti- 
cal motion to the star of light shown from A, is simultaneously 
made to produce periodical interruption of another intense light 
shown at B and seen ata third station, C, provided with a move- 
ment like that at B, the comparison from A to B may be ex- 
tended directly onward from B to C, and from C onward toa 
the probable error of a single comparison between the extremes : 
of a line of twenty stations may, I believe, be made smaller _ 
than the hundredth part of a second. — 
