range; and whoever will examine their banks carefully will do an important work for science. Indeed, very little is known accurately of the geology of Brazil. On the geological maps almost the whole country is represented as consisting of granite. If this be correct, it is very inconsistent with what we know of the geological structure of other continents, where the stratified rocks are in much larger proportions.” Upon this followed some account of the different kinds of valley formation and of terraces. “Do the old terraces above the rivers of South America correspond to the river terraces on any of our rivers,—those of the Connecticut, for instance,—showing that their waters had formerly a much greater depth and covered a much wider bottom? There must of course have been a cause for this great accumulation of water in ancient periods. I account for it in the northern half of the hemisphere by the melting of vast masses of ice in the glacial period, causing immense freshets. There is no trustworthy account of the river terraces in Brazil. Bates, however, describes flat-topped hills between Santarem and Pará in the narrow part of the valley, near Almeyrim, rising 800 feet above the present level of the Amazons. If this part of the valley were flooded in old times, banks might have been formed of which these hills are a remnant. But because such a theory might account for the facts it does not follow that the theory is true. Our work must be to study the facts, to see, among other things, of what these hills are built, whether of rock or of loose materials. No one has told us anything as yet of their geological constitution.”[7] To-day we have seen numbers of flying-fish from the deck, and were astonished at the grace and beauty of their motion, which we had supposed to be rather a leap than actual flight. And flight indeed it is not, their pectoral fins acting as sails rather than wings, and carrying them along on the wind. They skim over the water in this way to a great distance. Captain Bradbury told us he had followed one with his glass and lost sight of it at a considerable distance, without seeing it dip into the water again. Mr. Agassiz has great delight in watching them.[8] Having never before sailed in tropical seas, he enjoys every day some new pleasure.