Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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I Have Seen The Thermometer
Rise, On The Slope Of The Volcano Of Antisana, In The Kingdom Of
Quito, To 19 Degrees, When We Were 2837 Toises High.
M.
Labillardiere has seen it, on the edge of the crater of the peak of
Teneriffe, at 18.7 degrees, though he had used every possible
precaution to avoid the effect of accidental causes.
On the summit of the Peak, we beheld with admiration the azure
colour of the sky. Its intensity at the zenith appeared to
correspond to 41 degrees of the cyanometer. We know, by Saussure's
experiment, that this intensity increases with the rarity of the
air, and that the same instrument marked at the same period 39
degrees at the priory of Chamouni, and 40 degrees at the top of
Mont Blanc. This last mountain is 540 toises higher than the
volcano of Teneriffe; and if, notwithstanding this difference, the
sky is observed there to be of a less deep blue, we must attribute
this phenomenon to the dryness of the African air, and the
proximity of the torrid zone.
We collected on the brink of the crater, some air which we meant to
analyse on our voyage to America. The phial remained so well
corked, that on opening it ten days after, the water rushed in with
impetuosity. Several experiments, made by means of nitrous gas in
the narrow tube of Fontana's eudiometer, seemed to prove that the
air of the crater contained 0.09 degrees less oxygen than the air
of the sea; but I have little confidence in this result obtained by
means which we now consider as very inexact.
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