LETTER TO MR. PE1RCE. 695 



over the whole continent from north to south. 

 Among the facts already known from the 

 southern hemisphere are the so-called rivers 

 of stone in the Falkland Islands, which at- 

 tracted the attention of Darwin during his 

 cruise with Captain Fitzroy, and which have 

 remained an enigma to this day. I believe it 

 will not be difficult to explain their origin in 

 the light of the glacial theory, and I fancy 

 they may turn out to be ground moraines sim- 

 ilar to the ' horsebacks ' in Maine. 



" You may ask what this question of drift 

 has to do with deep-sea dredging ? The con- 

 nection is closer than may at first appear. If 

 drift is not of glacial origin, but is the pro- 

 duct of marine currents, its formation at once 

 becomes a matter for the Coast Survey to in- 

 vestigate. But I believe it will be found in 

 the end, that so far from being accumulated 

 by the sea, the drift of the Patagonian low- 

 lands has been worn av/ay by the sea to its 

 present outline, like the northern shores of 

 South America and Brazil." . . . 



This is not the place for a detailed account 

 of the voyage of the Hassler, but enough may 

 be told to show something of Agassiz's own 

 share in it. A journal of scientific and per- 

 sonal experience, kept by Mrs. Agassiz under 



