PlateIV.Graph: Mean Atmospheric Pressure at Para for 3 years.F. Reeve, imp.
PlateIV.
F. Reeve, imp.
The extreme variation of the barometer at Pará for three years was only three-tenths of an inch (see diagram,PlateIV.). The mean height, with all the necessary corrections, would seem to be almost exactly thirty inches; I have however already given my reasons for believing that there is a considerable difference in the pressure of the atmosphere in the interior of the country. In the month of May some very cold days are said to occur annually on the Upper Amazon and Rio Negro; but I never experienced anything of the kind very remarkable myself. Many intelligent persons have assured me that they sometimes are so severe that the inhabitants suffer much, and, what is much more extraordinary, the fishes in the rivers die of it. Allowing this to be the fact, I am quite unable to account for it, as it is difficult to conceive that a diminution of temperature of five or ten degrees, which is as much as ever takes place, can produce any effect upon them.
I have an authentic account of hail having once fallen on the Upper Amazon, a remarkable occurrence at a place only three degrees south of the equator, and about two hundred feet above the level of the sea. The children were out at play, and brought it to their parents, astonished at a substance falling from the clouds quite new to them, and which was so remarkably cold. The person who told me was a Portuguese, and his information can be perfectly relied on.