THE AMAZON VALLEY. 
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I unfortunately lost my thermometers, or had intended 
keeping a regular series of observations on the waters of 
the higher parts of the rivers I ascended. 
The extreme variation of the barometer at Para for 
three years was only three-tenths of an inch (see diagram, 
Plate IV.). 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 con- 
ceive that a diminution of temperature of five or ten de- 
grees, which is as much as ever takes place, can pro- 
duce 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, asto- 
nished at a substance falling from the clouds quite new 
to them, and which was so remarkably cold. The per- 
son who told me was a Portuguese, and his information 
can be perfectly relied on. 
