284 ANNUAL OF SCIENTIFIC DISCOVERY. 



PHYSICAL CHANGES IN THE CHARACTER OF THE NORTH 



AMERICAN CONTINENT. 



The following letter was directed to the Secretary of the New Tork His- 

 torical Society, by Professor Agassiz, in answer to an inquiry whether his 

 forthcoming work " Contributions to the Natural History of the United 

 States" would bear upon the civil history of our country. In reply Profess- 

 or Agassiz says : I hardly need remind you of the fact that the attention of 

 historians has but recently been called to the importance of considering the 

 physical character of the different parts of the world in connection with the 

 successive centuries of civilization and the primitive abode of the different 

 races of men. But there is one feature of this subject which has thus far been 

 entirely neglected. I allude to the character of the vegetation and the animal 

 creation in each natural area of the globe, which must at ah 1 times have 

 greatly influenced every where the progress of civilization, a picture of which 

 may in future be expected as a sort of frontispiece to the general history of 

 every great country. There are still other more general features yet little 

 known even to naturalists, which may in time add another charm to these 

 contemplations of the Kosmos the contrast between the different parts of the 

 world when compared with the previous conditions 01 our globe in successive 

 geological periods. For instance, Europe has a physical character now which 

 is not exemplified in any of the past ages of our earth,' while New Holland, 

 as it is now, reminds us of the condition of certain portions of Europe during 

 the middle geological ages (the Jurassic period in particular), and North 

 America recalls, both by its physical condition, its large lakes among others, 

 and its animals and plants, features prominent in Europe during the tertiary 

 times ; and I need only allude to the opossum, the snapping-turtle, the bull-frog, 

 the large salamanders, etc., the hickories, the swamp-cedar, the white gum- 

 tree, etc. all found in the tertiaries of Europe, and now entirely extinct there 

 to show the resemblance. Moreover, North America nourishes now a 

 number of fishes, and other animals, such as the king-crab, no representatives 

 of which are found alive in any other part of the globe, though they were 

 largely distributed over Europe in several geological periods. This character 

 of the North American fish fauna is so peculiar that, in alluding to it, I have 

 often been tempted to apply to it the epithet of old-fashioned. Two of these 

 curious fishes occur even in the State of New York the gar-pike and the so- 

 called mud -fish and the others are scattered over other parts of the country. 

 I shall, of course introduce a full account of these remarkable relics of past ages 

 in my new proposed work, for they throw as much light upon the physical 

 condition of former periods in the history of our globe, as the ruins of Egypt 

 and Nineveh would furnish upon the history of those periods in the life of 

 mankind, could they be restored to their former splendor before our gaze, and 

 studied in the full animation of their greatest prosperity, as we may investi- 

 gate our living animals. May I not add to all this that there are features in 

 the embryonic growth of animals which signify, as it were, the natural growth 

 of mankind ? So true is it that while civilization has gradually estranged 



