52 



power used, and you hear immediately the beats of the 

 elock registering themselves at each station. In order to 

 distinguish the beginning of the minute the fifty-eighth 

 second is omitted. In addition to this omission in the 

 Harvard Observatory system, the clock omits twenty-six 

 seconds immediately preceding of each five minutes. For 

 a single signal it is customary to resort to the time ball, 

 or to the time gun, both of which require considerable 

 mechanism which shall act automatically from the clock. 

 I think we can illustrate the first of these methods by 

 means of the simple ball you see suspended before you. 

 It should be electrically released the instant the second 

 hand of the clock reaches the beginning of the minute. 

 In regard to the gun, the Astronomer Royal for Scotland 

 observes, "You would do well, if you can, to pull the 

 trigger of a time-gun, for there are no means under 

 Heaven equal to a gun, for speaking to human nature and 

 obliging it to attend." 



We have extemporized also a gun in an adjoining yard, 

 which in the cause of science the clock should discharge 

 at the instant of the commencement of the next minute. 

 We have left untouched great divisions in the art of 

 measuring and disseminating time, but a regard for the 

 subject of my lecture reminds me I must close. Much 

 of the pleasure in the experiments of the evening is 

 owing to the generous help of Mr. R. W. Willson, of 

 the Department of Physics, and Mr. Winslow Upton, of 

 the Observatory of Harvard University. Are we not 

 reminded, in our efforts to measure an hour, that, "Time 

 is the measure of all things, but is itself immeasurable, 

 and the grand discloser of all things, but is itself undis- 

 closed?" 



