Vol. 70.] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxxiii 



and effect of the Glacial Epoch which some geologists had permitted them- 

 selves to make.' 



Turning his attention to the age and histoiy of the Earth, he 

 proceeded to investigate the frictional resistance experienced by 

 a tidal wave, and formed some important conclusions as to the 

 rigidity of the Earth as a whole, and as to the cumulative effect of 

 attractive forces acting on the parts of the Earth nearer to and 

 farther from the disturbing body. 



While unable, with existing evidence, to form an estimate having 

 any pretension to accuracy as to the present rate of tidal friction, 

 yet he was able to infer a gradual increase in the length of the day, 

 of the month, and of the obliquity of the ecliptic with a gradual 

 recession of the Moon from the Earth. He further calculated that 

 at a distance of time of not less than 54 million years, the Moon's 

 centre would have been only about 6000 miles distant from the 

 Earth's surface, while the day and the month would be of equal 

 duration, estimated at 5 hours 36 minutes. The further inference 

 followed that the Earth and the Moon had once formed a single 

 mass. Such a mass, gaining in rapidity of rotation as it contracted, 

 had split into two, and, according to his investigations of the 

 motions which would follow upon such a rupture, must have 

 developed a system bearing a strong resemblance to our own. 



Darwin then turned his attention more especially to the stresses 

 caused in the interior of the Earth by the weight of continents and 

 mountains, and found reason to believe that resistance to these 

 stresses implied a strength of material at least equal to that of 

 granite. 



Alfred B-ussel Wallace was born on January 8th, 1823. At 

 an early age he was attracted to the study of botany, but later on 

 became engrossed in entomology. This led to a journey to the 

 Amazon and Bio Negro, on the return from which his ship, with 

 all his collection, was destroyed by fire in mid-ocean, and his health 

 was temporarily shattered by exposure for ten days in an open boat. 

 Tn 1854, after his recovery, he visited the tropics, and made the 

 observations in Borneo, Sumatra, Java, the Celebes, New Guinea, 

 and Singapore which enabled him to produce his classic work on 

 the ' Geographical Distribution of Animals ' and his more popular 

 account of ' Island Life.' 



During these years Charles Darwin had been engaged in collecting 

 the facts on which his theory of natural selection was based. So 

 far back as 1844 he had outlined his views to Lyell and Hooker, 

 and had been urged by Lvell to publish them, lest he should be 



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