304 LIFE OF SIR JOHN LUBBOCK 



CH. 



Royal, on the subject. Sir Robert, however, 

 replies negatively, in an interesting letter : 



Observatory, Co. Dublin, 

 24 Sept. 1890. 



Dear Sir — I am much obliged for your kind letter. 



As to the date of the Ice Age I do not think the 

 astronomical data can help us much. The formula that 

 Croll used does not admit of such an extreme application 

 or " extrapolation." 



But I have lately been studying with the greatest 

 profit and delight Wright's Ice Age in North America, a 

 book which Cronkey recommended to me. He points 

 out that the Niagara Gorge has been cut since the ice, 

 and that Lake Erie was formed by the ice. The time 

 required to cut seven miles from Lake Ontario to 

 Niagara seems to be the most reliable method of measur- 

 ing the date of the Ice Age. At a foot a year (Ly ell's 

 estimate, I believe) this means 35,000 years, but Wright 

 gives good grounds for his opinion that it may not be 

 more than 7000 ! 



As the facts which my little book is intended to set 

 forth are (in the main) beyond a question, I thought it 

 wiser to avoid matters about which there could be much 

 uncertainty. I am half inclined, however, to attempt a 

 summary of Wright's views, and if I do so I will trespass 

 on your kindness to look over what I say. A few years 

 ago I spent a week at Niagara, and the novelty of 

 Wright's views makes me long to go there again. This 

 year I was in Norway and the contrast between the 

 Fiords before the Ice and Niagara Gorge since is very 

 striking. 



Wright's book has interested me quite as much as 

 Geikie's Great Ice Age, and that is saying a great deal. 



The arrangement of my pages will show you that 

 when I began I did not intend to trouble you with so 

 long a letter. Pray excuse it — and believe me, yours 

 truly, Robert S. Ball. 



Sir John Lubbock. 



The following is worthy of quotation for the 

 interest of its subject-matter, though the " map " 

 which it is its principal purpose to suggest is not 

 shown. 



