NO. 6 AGE OF THE EARTH BECKER 3 



attention to the discrepancy between stratigraphical estimates and those 

 from sodium accumnlation in the ocean. If Mr. Walcott's estimate for 

 time since the base of the Cambrian bo doubled^ in accordance with the 

 opinions stated above, it gives 55 million years. 



The introduction into modern geology of estimates founded on chemical 

 denudation is due to T. Mellard Reade/ but Mr. J. Joly was the first to 

 show that sodium is the only element which can be trusted to afford good 

 estimates of the lapse of time involved in denudation. Adopting the 

 hypothesis that the sodium content of the ocean is derived at a constant 

 rate from that of the rocks, Mr. Joly, in 1899, arrived at an age of 

 between 80 and 90 million years, and this he increased by 10 million in 

 1900.^ In 1909 Mr. Sollas made a very searching inquiry into this sub- 

 ject, availing himself of much material published since Mr. Joly's papers, 

 and, on tlie same hypothesis of uniformity, placed the age of the ocean 

 between 80 million and 150 million years.' 



Very curiously, the great astronomer Edmund Halley nearly 200 years 

 ago devised a method of determining the age of the ocean from the 

 amount of salt which it contains.* He recognized that the means he pro- 

 posed for determining the annual increment of salt were impracticable 

 and, writing long before Lavoisier was born, could not have guessed that 

 analysis of river waters would become a simple matter. It is not strange 

 that Halley's paper was completely forgotten, but it is now of such in- 

 terest and is so inaccessible to a majority of geologists that an extract 

 from it will not be regarded as out of place here. 



A short Account of the Cause of the Salt7iess of the Ocean, and of the several 



Lakes that emit no Rivers; with a Proposal, t>y help thereof, to discover 



the Age of the World. 



There have been many attempts made and proposals offered, to ascertain 



from the appearances of nature, what may have been the antiquity of this 



globe of earth; on which, by the evidence of sacred writ, mankind has dwelt 



about 6000 years; or according to the Septuagint above 7000 This 



inquiry seeming to me well to deserve consideration, and worthy the thoushts 

 of the Royal Society, I shall take leave to propose an expedient for determining 

 the age of the world by a medium, as I take it, wholly new, and which in my 

 opinion seems to promise success, though the event can not be judged of till 

 after a long period of time; submitting the same to their better judgment. 

 What suggested this notion was an observation I had made, that all the lakes 

 in the world, properly so called, are found to be salt, some more some less than 

 the ocean sea, which in the present case may also be esteemed a lake; since by 

 that term I mean such standing waters as perpetually receive rivers running 

 into them, and have no exit or evacuation 



1 Proc. Liverpool Geol. Soc, vol. .3, 1S76, p. 211. 



2 Trans. Roy. Soc. Dublin, vol. 7, 1899. p. 23; and Brit. Assoc. Adv. Sci., 1900, p. 369. 



* Quart. Jour. Geol. Soc. London, vol. 65, 1909, p. CXII. 



* Phil. Trans., vol. 29, 1715, p. 296. See also Science, vol. 31, 1910, p. 459. 



