. . .I have waited to write until I should have some facts sufficiently important to claim your attention. In truth, the study of the marine animals, which I am, for the first time, able to observe in their natural conditions of existence, has engrossed me almost exclusively since I came to the United States, and only incidentally, as it were, I have turned my attention to paleontology and geology. I must, however, except the glacial phenomena, a problem, the solution of which always interests me deeply. This great question, far from presenting itself more simply here, is complicated by peculiarities never brought to my notice in Europe. Happily for me, Mr. Desor, who had been in Scandinavia before joining me here, called my attention at once to certain points of resemblance between the phenomena there and those which I had seen in the neighborhood of Boston. Since then, we have made several excursions together, have visited Niagara, and, in short, have tried to collect all the special facts of glacial phenomena in America. . .You are, no doubt, aware that the whole rocky surface of the ground here is polished. I do not think that anywhere in the world there exist polished and rounded rocks in better preservation or on a larger scale. Here, as elsewhere, erratic debris are scattered over these surfaces, scratched pebbles impacted in mud, forming unstratified masses mixed with and covered by large erratic boulders, more or less furrowed or scratched, the upper ones being usually angular and without marks. The absence of moraines, properly so-called, in a country so little broken, is not surprising; I have, however, seen very distinct ones in some valleys of the White Mountains and in Vermont. Up to this time there had been nothing very new in the aspect of the phenomena as a whole; but on examining attentively the internal arrangement of all these materials, especially in the neighborhood of the sea, one soon becomes convinced that the ocean has partially covered and more or less remodeled them. In certain places there are patches of stratified sand interposed between masses of glacial drift-deposit; elsewhere, banks of sand and pebbles crown the irregularities of the glacial deposit, or fill in its depressions; in other localities the glacial pebbles may be washed and completely cleared of mud, retaining, however, their markings; or again, these markings may have disappeared, and the material is arranged in lines or ramparts, as it were, of diverse conformation, in which Mr. Desor recognized all the modifications of the "oesars" of Scandinavia. The disposition of the oesars, as seen here, is evidently due entirely to the action of the waves, and their frequency along the coast is a proof of this. In a late excursion with Captain Davis on board a government vessel I learned to understand the mode of formation of the submarine dikes bordering the coast at various distances, which would be oesars were they