143 - 
pieces beneath our feet. Tue atmofohe- 
ric air and the humid lands (all thefe vol- 
canoesare in adecompojed porphyry,) ap- 
pear the great agents of thele combuitions, 
of thefe fubterraneous fermentations. Hi- 
herto it was believed at Quito, that 2470 
toiles was the greateit height where men 
could refit the rarefaGiion of the air. In 
the month of March-180z, we {pent fome 
days in the vait plains which furreund the 
volcano of Antifana at 2107 toifes, where 
the cattle, when puriued, often vomit 
blood. The 16th of March we difcerned 
a path on.the fnow, a gentle flupe, on 
which we mounted to the height of 2773 
tolfes.. The air.contained 0,008 of car- 
bonic-acid, 0,218 of oxigen, and 0,774 
of azote. The thermometer cf Reaumur 
was only at 15° 3 it was not in the leatt 
cold, yet we bled at lips and eyes. The 
fite did not permit us to make an experi- 
ment with the compals of Borda, but ina 
grotto at 24.67 toifes. The intenfity of 
magnetic power was greater at that height 
tian at Quito, in theratio of 230 to 218. 
But it ts not to be forgot, that often the 
number of ofcillaticns increafes when the 
inclination diminifhes, and that this inten« 
iity is increafed by the ma{s of the moun- 
tain whofe porphyries affect the magnetic- 
needle. 
in the expedition I made on the 23d of 
June 1802, to the Chimborazo, we have 
experienced that with patience one may 
fupport a (till greater rarefaétion of air.— 
We reached to a greater height than La 
ondamine (on the Corazon,) by 500 
toifes. We carried infiruments on the 
himborazo to 3031 toifes ; feeing the, 
mercury defcend in the barometer to 13 
inches 11, 2 lines ; the thermometer be- 
4ng 1° 3’ below zero. We bled ill at our 
lips. Our Indians forfook us as ufual.— 
Citizen Bompland and M. Montufon, fon 
of the Marquis of Selvalegre at Quito, 
were the only people who perfifted : we all 
felt an uneafinefs, acebility, an inclination 
to vomit, which certainly proceeds from 
the defect of oxygen in thefe regions more 
than from the rarified air. T found only 
0.20 of oxygen at this immeafe height.— 
A horrid fiflure prevented us from 1each- 
ing to the very fummitot Chimborazo, 
from which we were only 206 toifes. You 
know that the height of this coloffal mafs 
is fill uncertain. La Condamine meafur- 
ed it from a great diftance. He allows it 
nearly 3220 toifes. Don George Juan 
gives it 3380. ‘This difference does not 
proceed from the various altitudes which 
thefe aftronomers adopt for the fignal of 
Carabouron. J meafured in the plain of 
. 
Proceedings of Learned Societies. 
[Sept. t, 
Taffiaa bafe of 1702 metres, (forgive 
me for fpeaking fometimes of toifes and 
fometimes of metres, according to the dif- 
ference of the intruments Tuie : you may 
be fure that in publifling my operations 
J fhall reduce the whole to the metre and 
to the centigrade thermometer). . Two 
geodefical operations give me Chimborazo 
3267 toifes above the fea: but the calcu- 
lation mutt be rectified by the diftance of 
the feGtant from the artificial horizon, and 
other.circumftances. 
The volcano Tongouragoa has dimi- 
nifh«d much tince the time of La Conda- 
mine ; inflead of 2620 toifes, I find it oi- 
ly 25313 and I hope this difference does 
not proceed from an error in my opera- 
tions ; fince in my meafures of Cayambo, 
Antifana, Cotopaxi, and Lilinga, I do not 
differ more than ro or 15 toiles from the 
retult of La Condamine and Bouguer.— 
All the inhabitants of thefe miterable 
countries fay that Tongouragoa 1s percep- 
tibly lower, while Cotopaxi, which has 
had fo violent explofions, is as high as in 
1744, and even fomewhat higher, unilefs 
that arife from an error on my fide. But 
the rocky fummit of Cotopaxi fhews that 
it is a chimney which refifts and preferves 
itsfigure. The operations we have made 
in the Andes of Quito, from January to - 
July, brought the innabitants the fad news 
that the crater of Pichincha, which La 
Condamine {aw full of fmow, burns anew 5 
and that Chimborazo, whom they thoughe 
fo peaceable and harmlefs, has been a vol- 
cano, and perhaps one day will be fo 
again. We have burnt rock and pumice- 
fone at the height of 3031 toifes. Woe 
to mankind. if the volcanic-fire (for we 
may fay that the flat of Quito has been 
one volcano with feveral tops;) breaks 
forth through the Chimborazo. It has 
of:en been faid in print that this mountain 
is of granite ; but there is not one atom 
of that. Itis here and there porphyry in 
columns, encruftating vitrous field-fpath, 
horn-ftone, and olivin. The bed of porphy- 
ry is 1900 tones thick. I might mention 
to you on this occafion a polar porphyry, 
which, analogous to the ferpentine I have 
defcribed in the ournal de Phyfique, has 
poies without attra€tion: J might quote 
to you other faéts relating to the great 
law of the ftratas, and their enormous 
thicknefs near the equator : but it would 
be too much in a letter whichmay be loft; 
aad I will treat cf that fome other time, — 
I only add, that befides the elephants’- 
teeth which we have fent to Citizen Cu- 
vier from the flats of Santa Fé, of 1350 
toifes in height, we keep for him — 
- ill 
