340 POPULAR SCIENCE MONTHLY. 



stract work was consciously for the benefit of the community, and he 

 ever sought opportunity to make its results directly available. In pro- 

 moting the interests of the people of his adopted State he incidentally 

 accomplished much for a larger community by helping it to an apprecia- 

 tion of the essential beneficence of the scientific study of nature and 

 man. As an individual he was a diligent and successful laborer in the 

 field which the association cultivates, and when the association selected 

 him as its standard-bearer it made choice of one who was peculiarly its 

 representative. 



The subject to which I shall invite your attention this evening is by 

 no means novel, but might better be called perennial or recurrent; for 

 the problem of our earth's age seems to bear repeated solution without 

 loss of vigor or prestige. It has been a marked favorite, moreover, with 

 presidents and vice-presidents, retiring or otherwise, when called upon 

 to address assemblies whose fields of scientific interest are somewhat 

 diverse — for the reason, I imagine, that while the specialist claims the 

 problem as his peculiar theme of study, he feels that other denizens of 

 the planet in question may not lack interest in the early lore of their 

 estate. 



The difficulty of the problem inheres in the fact that it not only 

 transcends direct observation, but demands the extrapolation or exten- 

 sion of familiar physical laws and processes far beyond the ordinary 

 range of qualifying conditions. From whatever side it is approached, 

 the way must be paved by postulates, and the resulting views are so 

 discrepant that impartial onlookers have come to be suspicious of these 

 convenient and inviting stepping stones. 



That vain expectation may not be aroused, I admit at the outset 

 that I have not solved the problem and shall submit to you no esti- 

 mates. My immediate interest is in the preliminary question of the 

 available methods of approach, and it leads to the consideration of the 

 ways, or the classes of ways, in which the measurement of time has 

 been accomplished or attempted. 



Of the artificial devices employed in practical horology there are 

 two so venerable that their origins are lost in the obscurity of legendary 

 myth. These are the clepsydra and the taper. In the clepsydra advan- 

 tage is taken of the approximately uniform rate at which water escapes 

 through a small orifice, and time is measured by gaging the loss of 

 water from a discharging vessel or the gain in a receiving vessel. The 

 hour-glass is one of its latest forms, in which sand takes the place of 

 water. The taper depends for its value as a timepiece on the approxi- 

 mate uniformity of combustion when the area of fuel exposed to the 

 air is definitely regulated. It survives chiefly in the prayer stick and 

 safety fuse, but the graduated candle is perhaps still used to regulate 

 monastic vigils. 



