I cannot say good by to Teffé without a word in commemoration of one class of its inhabitants who have interfered very seriously with our comfort. There is a tiny creature called the Mocuim, scarcely visible except for its bright vermilion color, which swarms all over the grass and low growth here. It penetrates under the skin so that one would suppose a red rash had broken out over the body, and causes excessive itching, ending sometimes in troublesome sores. On returning from a walk it is necessary to bathe in alcohol and water, in order to allay the heat and irritation produced by these little wretches. Mosquitoes are annoying, piums are vexatious, but for concentrated misery commend me to the Mocuim. _October 23d._—We left Teffé on Saturday evening on board the Icamiaba, which now seems quite like a home to us; we have passed so many pleasant hours in her comfortable quarters since we left Pará. We are just on the verge of the rainy season here, and almost every evening during the past week has brought a thunder-storm. The evening before leaving Teffé we had one of the most beautiful storms we have seen on the Amazons. It came sweeping up from the east; these squalls always come from the east, and therefore the Indians say “the path of the sun is the path of the storm.” The upper, lighter layer of cloud, travelling faster than the dark, lurid mass below, hung over it with its white, fleecy edge, like an avalanche of snow just about to fall. We were all sitting at the doorstep watching its swift approach, and Mr. Agassiz said that this tropical storm was the most accurate representation of an avalanche on the upper Alps he had ever seen. It seems sometimes as if Nature played upon herself, reproducing the same appearances under the most dissimilar circumstances. It is curious to mark the change in the river. When we reached Teffé it was rapidly falling at the rate of about a foot a day. It was easy to measure its retreat by the effect of the occasional rains on the beach. The shower of one day, for instance, would gully the sand to the water’s edge, and the next day we would find the water about a foot below the terminus of all the cracks and ruts thus caused, their abrupt close showing the line at which they met the water the previous day. Ten days or a fortnight before we left, and during which we had heavy rains at the close of every day, continuing frequently through the night, those oscillations in the river began, which the people here call “repiquete,” and which, on the Upper Amazons, precede the regular rise of the water during the winter. The first repiquete occurs in Teffé toward the end of October, accompanied by almost daily rains. After a week or so the water falls again; in ten or twelve days it begins once more to ascend, and sinks again after the same period. In some seasons there is a third rise and fall, but usually the third repiquete begins the permanent annual rise of the river. On board the steamer we were