length; no doubt coming down to make their chrysalids in the sand. We returned to the steamer at ten o’clock; and, after breakfast, finding our anchorage-ground somewhat rough as the tide came in, we went a little higher up, and entered the Bahia do Sul. Here again we went on shore to see the net drawn, this time more successfully. We should have had a delightful walk on the beach again, had it not been for hosts of minute flies which hovered about us, and had a power of stinging quite disproportionate to their size. On returning we met with an unforeseen difficulty. The tide had been falling during our walk, and the canoe could not approach the beach within several yards. The gentlemen plunged in, and walked out over knees in water; while the boatmen made a chair of their arms and carried me through the surf. _March 5th._—Our excursion in the harbor closed with a visit to the small island of Tatuatuba, distant about six miles from Pará. In order to examine the shores, we made the circuit of the island on foot. Here again the same geological structure presented itself; and there was one spot in particular where the sharp, vertical cut of the bank facing the beach presented an admirable section of the formations so characteristic of the Amazonian Valley; the red, sandy clay of the upper deposit filling in all the undulations and inequalities of the sandstone below, the surface of which was remarkably irregular. The sea is making great encroachments on the shore of this island. Senhor Figueiredo, who lives here with his family and by whom we were received with much hospitality, told us that during the last eighteen or twenty years, the beach had receded considerably in some places; the high-water line being many yards beyond its former limit. The result of this excursion has shown that, with the exception of some low mud-islands nearly level with the water, all the harbor islands lying in the mouth of the Amazons are, geologically speaking, parts of the Amazonian Valley, having the same structure. They were, no doubt, formerly continuous with the shore, but are separated now, partly by the fresh waters cutting their way through the land to the ocean, partly by the progress of the sea itself.