Page:A narrative of travels on the Amazon and Rio Negro.djvu/113

 just in time for supper, and were heartily received by Senhor Calistro. After a few days more I left his hospitable roof, loaded with luxuries: eggs, tapioca, a roast pig, pine-apples, and sweets were sent to my canoe; and I bade adieu with regret to my kind host.

On our way down I again encountered the "piroróco" when I hardly expected it. We had gone in shore at a sugar estate to wait for the tide, when the agent told us we had better put out further into the stream, as the piroróco beat there. Though thinking he only wished to frighten us, we judged it prudent to do as he advised; and while we were expecting the tide to turn, a great wave came suddenly rushing along, and breaking on the place where our canoe had been at first moored. 'The wave having passed, the water was as quiet as before, but flowing up with great rapidity. As we proceeded down the river, we saw everywhere signs of its devastations in the uprooted trees which lined the shores all along, and the high mud-banks where the earth had been washed away. In winter, when the spring-tides are highest, the "piroróco" breaks with terrific force, and often sinks and dashes to pieces boats left incautiously in too shallow water. The ordinary explanations given of this phenomenon are evidently incorrect. Here there is no meeting of salt and fresh water, neither is the stream remarkably narrowed where it commences. I collected all the information I could respecting the depth of the river, and the shoals that occur in it. Where the bore first appears there is a shoal across the river, and below that, the stream is somewhat contracted. 'The tide flows up past Para with great velocity, and entering the Guama river comes to the narrow part of the channel. Here the body of tidal water will be deeper and flow faster, and coming suddenly on to the shoal will form a wave, in the same manner that in a swift brook a large stone at the bottom will cause an undulation, while a slow-flowing stream will keep its smooth surface. This wave will be of great size, and, as there is a large body of water in motion, will be propagated onwards unbroken. Wherever there are shallows, either in the bed or on the margin of the river, it will break, or as it passes over slight shoals will be increased, and, as the river narrows, will go on with greater rapidity. When the tides are low, they rise less rapidly, and at the commencement a much less body of