of the mountain is
perfectly pure and respirable. The pestilential vapours themselves would
appear to be nothing more than carbonic acid gas. The people attached to
the embassy told us that when there is any wind, the vapours are scarcely
perceptible, but that they are very dangerous when the weather is calm
and serene. Carbonic acid gas being, as the reader is aware, heavier
than the atmospheric air, necessarily condenses on the surface of the
ground, and remains fixed there until some great agitation of the air
sets it in movement, disperses it in the atmosphere, and neutralizes its
effects. When we crossed the Bourhan-Bota, the weather was rather calm
than otherwise. We remarked, that when we were lying on the ground,
respiration was much more difficult; when, on the contrary, we raised
ourselves on horseback, the influence of the gas was scarcely felt. The
presence of the carbonic acid rendered it very difficult to light a fire;
the argols burned without flame, and threw out great quantities of smoke.
As to the manner in which the gas is formed, or as to whence it comes, we
can give no sort of idea. We will merely add, for the benefit of those
who are fond of seeking explanations of things in their names, that
Bourhan-Bota means Kitchen of Bourhan; Bourhan being a synonyme of
Buddha.

During the night we passed on the other side of the mountain, there fell
a frightful quantity of snow. Our companions, who had not ventured to
ascend the entire mountain at once, rejoined us in the morning; they
informed us that they had effected the ascent of the upper portion of the
mountain easily enough, the snow having dispersed the vapour.

The passage of the Bourhan-Bota was but a sort of apprenticeship. A few
days after, Mount Chuga put our strength and courage to a still more
formidable test. The day's march being long and laborious, the cannon
shot, our signal for departure, was heard at one o'clock in the morning.
We made our tea with melted snow, ate a good meal of tsamba, seasoned
with a clove of garlic, cut up into small bits, and started. When the
huge caravan first set itself in motion, the sky was clear, and a
brilliant moon lit up the great carpet of snow with which the whole
country was covered. Mount Chuga being not very steep in the direction
where we approached it, we were able to attain the summit by sunrise.
Almost immediately afterwards, however, the sky became thickly overcast
with clouds, and th