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ONCE had an opportunity, while traveling upon the Amazon, to observe some of the effects of a remarkable phenomenon which occurs at the northern mouth of that river in connection with the spring tides. It is known to the Indians and Brazilians as the pororóca, and is, I believe, generally supposed to be caused in the same manner as the "bore" of the Hoogly branch of the Ganges, of the Brahmapootra, and of the Indus, I regret very much that, like Condamine, who passed through this region in 1740, I could not observe this phenomenon in actual operation; but the gentleman whose guest I was at the time, and upon whose boat I was a passenger, was fairly horrified at my suggesting such a thing, while his boatmen united in a fervent "God forbid that we should ever see the pororóca!" and ever afterward doubted my sanity. I give some of the results of my observations, however, as collateral evidence, and in order that those who in the future visit this particular part of the Amazon Valley, concerning which so little is known, may be able to see and establish as far as possible the rate of destruction and building up here being carried on.

I was upon a trip from Macapá—a small town on the northern bank of the Amazon, and about one hundred miles from its mouth—down the river to the ocean, and thence up the Rio Araguarý as far as the last might be navigable. The one inhabited place on the Araguarý is a very small military colony, called the Colonia Militar Pedro Segundo. At Macapá I became acquainted with the then director of this colony, Lieutenant Pedro Alexandrino Tavares, and was invited by him to visit the Araguarý.

The trip from Macapá was by a small sail-boat down the Amazon to the ocean, and thence up the Araguarý. Our departure was so timed that we should reach that part of the region disturbed by the pororóca exactly at the time of the month when there would be the least probability of its being met with—that is, at the time of the neap tides. The voyage down the river was in the face of the wind, and it was only five days after leaving