250 LOUIS AGASSIZ. 



lie married Miss Elizabeth Gary, of Boston, a lady of great intelligeuce, 

 who becauie the inseparable companion of his travels and of his work. 



The exploration of America was a vast field opened to him, and he 

 devoted to this work a very important part of his time. In 1848 he un- 

 dertook the charge of a scientific expedition to Lake Superior. Seven- 

 teen persons started on this exploration in a country the geography 

 and natural history of which were still very little known. The zoology, 

 the botany, the general cliaracter of the country and the indigenous in- 

 habitants, the influence even of the x)rogress of civilization upon the 

 aspect of the countrj", upon the character of the fauna and of the flora, 

 all were observed, recorded, discussed ; nothing of importance escaped 

 the eager and masteily eye of the chief of the expedition.* 



The history of the journey was made by Mr. Cabot; the shells, insects, 

 and birds collected were studied by various collaborators. Agassiz de- 

 voted especial attention to the general characteristics of the vegetation, 

 in order that he might compare it with that of the Jura and the Alps; 

 to the fishes, the study of which wherever he went always captivated 

 him; to some new reptiles, and finally to the phenomena of erratic 

 bovvlders in this region, which his knowledge of the glacial district of 

 Europe permitted him to prove belonged to a remarkable extension of 

 the same system. 



The Americans have devoted for a long time especial attention to the 

 study of the shores of their continent. The department of the govern- 

 ment occupied with what is called the United States Coast Survey is 

 now known all over the world on account of the great importance of 

 the work it has accomplished. It united to a geographical knowl- 

 edge of the coast a scientific study of the neighboring region, often 

 j)ursued under great difficulties. Agassiz from the first was interested 

 in this species of investigation. In 1850 he was commissioned by Dr. 

 Baclie, director of the survey, to study the coral reefs of Florida. He 

 examined upon the spot the development of the Polyp, which had cre- 

 ated around this peninsula four concentric banks, the formation of 

 which he found had been successive. According to the mode of increase 

 of these animals, he could calculate safely within the limits of truth 

 that these reefs had been at least thirty thousand years in forming. 

 The outer reef, still in process of development, is constituted of the liv- 

 ing coral. The animals belong to various types, each of which is limited 

 to a certain depth beyond which it cannot exist. The deepest are the 

 Astrseans, next the Meandrines; at the surface are the Madrepores, not 

 more than two or three yards below the surface of the water and cover- 

 ing vast spaces with their beautiful growth. Other animals become 

 attracted to the coral branches. The sea breaks oft" the coral and throws 

 the fragments upon the reef, which is little by little covered with soil, 



* Louis Agassiz. ''Lake Superior, its pliysical cliaracter, yegetatiou, and animals, 

 compared witli tliose of otlier and similar regions. 1850." 



