They swarmed around us, and by the light of the fire, the blanket bags in which the men sought to protect themselves, seemed literally black with their crawling and stinging persecutors. Woe to the unhappy wretch who had left unclosed the least hole in his bag; the persevering mosquitoes surely found it out, and as surely drove the luckless occupant out of his retreat. I noticed one man dressed as if in the frozen north, hold his bag over the fire till it was quite full of smoke, and then get into it, a companion securing the mouth over his head at the apparent risk of suffocation; he obtained three hours of what he gratefully termed comfortable sleep, but when he emerged from his shelter, where he had been stewed up with the thermometer at 87 degrees, his appearance may be easily imagined. Our hands were in constant requisition to keep the tormentors from the face and ears, which often received a hearty whack, aimed in the fruitless irritation of the moment at our assailants, and which sometimes ended in adding headache to the list of annoyances. Strike as you please, the ceaseless humming of the invincible mosquito close to your ear seems to mock his unhappy victim! One poor fellow, whose patience was quite exhausted, fairly jumped into the river to escape further persecution. We had the wind from South-West to South-East during the afternoon, but at 6 P.M. it veered round to North-North-West. While getting the observations for time and latitude, some of us were compelled to remain quiet, an opportunity our tiny assailants instantly availed themselves of, covering our faces and hands. To listen quietly to their hum, and feel their long stings darting into your flesh, might put the patience of Job himself to a severe trial. ASCENT OF THE FITZROY. March 10.