part of the heavens, yet we had a light shower of rain of more than an hour's continuance. The temperature of the dew-point by Daniell's hygrometer being 72°, that of the air 74°.
In addition to our almost daily experiments on the temperature of the ocean to the depth of six hundred fathoms, we had made several fruitless attempts to obtain soundings as we passed through the tropics. These repeated failures were principally occasioned by the want of a proper kind of line, but they served to point out to us that which was most suitable. I accordingly directed one to be made on board, three thousand six hundred fathoms, or rather more than four miles in length, fitted with swivels to prevent it unlaying in its descent, and strong enough to support a weight of seventy-six pounds.
1840.
Jan. 3.On the 3d of January, in latitude 27° 26′ S., longitude 17° 29′ W., the weather and all other circumstances being propitious, we succeeded in obtaining soundings with two thousand four hundred and twenty-five fathoms of line, a depression of the bed of the ocean beneath its surface very little short of the elevation of Mount Blanc above it.
