From an after-investigation, I am led to believe that the cause of this phenomenon arises from the fact that the trade-winds are dammed up by the Andes, and that the atmosphere in those parts is, from this cause, compressed, and consequently heavier than it is farther from the mountains, though over a less elevated portion of the earth. The discovery of this fact has led me to place little reliance in the indications of the barometer for elevation at the eastern foot of the Andes. It is reasonable, however, to suppose that this cause would no longer operate at Egas, nearly one thousand miles below the mouth of the Huallaga.
I shall, therefore, give the height of Egas above the level of the sea, from the temperature of boiling water, (208°.2,) at two thousand and fifty-two feet. Egas is about eighteen hundred miles from the sea; this would give the river a descent of a little more than a foot per mile, which would about give it its current of two and a half miles per hour.
December 29.—We drifted with the current, and a little paddling on the part of the crew, until 10 p. m., when we made fast to a tree on the right bank.
December 30.—We started at 5 a. m. At 3 p. m., where the river was quite a mile wide, I found but thirty feet in mid-channel; and about two hundred yards on our right hand was a patch of grass, with trees grounded on it. At 6 p. m., I judged from the appearance of the shores on each side (bold, red cliffs) that we had all the width of the river. It was only about a mile wide, and I thought it would be very deep; but I found only sixty feet. I could not try the current for the violence of the wind. At seven arrived at the mouth of the Lake Coari, one hundred and fifteen miles from Egas, and made fast to a schooner at anchor near the right bank.
This schooner seemed to have no particular owner or captain, but to be manned by a company of adventurers; for all appeared on an equality. They were from Obidos, upwards of two months; and twenty-eight days from Barra, which place we reached from here in five. They were travelling at their leisure, but complained much of the strength of the current and the want of strength of the easterly winds. I heard the same complaints at Egas, but I have found the winds quite fresh from the eastward, and the current, compared with that above, slight. But there is a wonderful difference in the estimation of a current, or the strength of a wind, when voyaging with and against them.
The fault of the vessels navigating the Amazon is the breadth of beam and want of sail. I am confident that a clipper-built vessel, sloop, or rather ketch-rigged, with a large mainsail, topsail, topgallant-sail, and studding sails—the last three fitted to set going up before the wind, and to strike, masts and all, so as to beat down with the current under mainsail, jib, and jigger—would make good passages between Pará and Egas. The vessels used now on the river are built broad and flat-bottomed, to warp along shore when the wind is light or contrary. Their sails are much too small, and are generally made of thin, bad material.
December 31.—We pulled into the Lake of Coari; but being told that it would take nearly all day to reach the village of Coari, and that it was an insignificant place, where I would get neither supplies nor information, I decided not to go.
It may seem strange that just out of Egas I should need supplies, but all I could purchase there were half a dozen fowls, four turtles, and some farinha; and upon opening the baskets of farinha, it was found to be so old and sour that, though the Indians could eat it, I could not; and thus we had no bread, nor even the substitute for it—plantains and farinha; and had to eat our meat with some dried peas that we fortunately found at Egas.
The entrance to the Lake of Coari is about four hundred yards wide, and half a mile long. It expands, particularly on the right hand, suddenly into the lake, which at once shows itself six or seven miles wide, having a large island extending apparently nearly across it. The entrance has forty-two feet of depth in the middle, and, being faced by an island at both mouths, (the one into the lake, the other into the river,) appears land-locked, and makes a beautiful harbor. The banks are very low, of a thin, sandy soil, covered with bushes; and the right bank is perforated with small channels, running into the Amazon. The water of the lake is beautifully clear, and of a brown color; it runs into the Amazon at the rate of three-fourths of a mile per hour.
We pulled up the right bank of the lake about a mile, and stopped at a little settlement of ten or twelve houses, but could get nothing. The people seemed afraid of us, and shut their doors in our faces. The lieutenant, or principal man of the place, said that if we would give him money, he would send out and get us some fowls and plantains; but as he was a little drunk at this hour, (seven in the morning,) I would not trust him. We breakfasted, and sailed at 11.