1002 



SCIENCE. 



[N. S. Vol. XI. No. 287. 



does not always itself recognize, that pure 

 science is fundamentallj' the creature and 

 servant of the material needs of mankind, 

 and it thus stands for what might be called 

 the human side of science. Edward Or- 

 toa, throughout his career as teacher and 

 investigator, was conspicuous for his atten- 

 tion to the human side of science. His 

 most abstract work was consciously for the 

 benefit of the community, and he ever 

 sought opportunity to make its results di- 

 rectly available. In promoting the inter- 

 ests of the people of his adopted state he in- 

 cidentally accomplished much for a larger 

 community by helping it to an appreciation 

 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 pres- 

 idents and vice-presidents, retiring or other- 

 wise, when called upon to address assem- 

 blies whose fields of scientific interest are 

 somewhat diverse — for the reason, I imag- 

 ine, 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 extension of familiar phj'sical 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 j'ou no 

 estimates. 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 venera- 

 ble that their origins are lost in the obscur- 

 ity of legendary myth. These are the 

 clepsydra and the taper. In the clepsydra 

 advantage 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 later forms, in 

 which sand takes the place of water. 

 The taper depends for its value as a time 

 piece on the approximate uniformity of 

 combustion when the area of fuel exposed 

 to the air is definitely regulated. It sur- 

 vives chieflj- in the prayer stick and safety 

 fuse, but the graduated candle is perhaps 

 still used to regulate monastic vigils. 



The pendulum, a comparatively modern 

 invention, excelling the clepsydra and 

 taper in precision, has altogether sup- 

 planted them as the servant of civilization. 

 Its accuracy results from the remarkable 

 property that the period in which it com- 

 pletes an oscillation is almost exactly the 

 same, whatever the arc through which it 

 swings. It regulates the movements not 

 only of our clocks, watches and chronom- 

 eters, but of barographs, thermographs and 

 a great variety of other machines for re- 

 cording events and changes in their proper 

 order and relation in respect to time. 



