(4.) Parallel for parallel, the southern hemisphere from the equator to 40° or 45° S., is the cooler. This fact is consistent with the supposition that the heat that is rendered latent and abstracted from that hemisphere by its vapours is set free by their condensation in this. Upon no other hypothesis than by these supposed crossings can this fact he reconciled, for the amount of heat annually received from the sun by the two hemispheres is, as astronomers have shown, precisely the same.[1]
(5.) Well-conducted observations made with the hydrometer[2] (§ 285) for every parallel of latitude in the Atlantic Ocean from 40° S. to 40° N., show that, parallel for parallel, and notwithstanding the difference of temperature, the specific gravity of sea-water is greater in the southern than it is in the northern hemisphere. This difference as to the average condition of the
- ↑ The amount of solar heat annually impressed upon the two hemispheres is identically the same; yet within certain latitudes the southern hemisphere is, paralled for parallel, the cooler. How does it become so? If it be the cooler by radiation, then it must be made so by radiating more heat than it receives; such a process would be cumulative in its effects, and were it so, the southern hemisphere would be gradually growing cooler. There is no evidence that it is so growing, and the inference that it is seems inadmissible. In fact, the southern hemisphere radiates less heat than the northern, though it receives as much from the sun. And it radiates more, for this reason: there is more land in the northern—land is a better radiator than water—therefore the northern radiates more heat than the southern hemisphere; the southern has more water and more clouds—clouds prevent radiation—therefore the southern hemisphere radiates less heat than the northern; still it is the cooler. How is this paradox to be reconciled but upon the supposition that the southern surplusage is stowed away in vapours, transported thence across the calm belts by the winds, and liberated by precipitation on our side of the equator?
- ↑ Rodgers, in the Vincennes. Maury's Sailing Directions, 8th ed., vol. i., p. 235.
1 to 1½ mm. large, mm. thick, and weighing 1½ milligrams. Our famous microscopist and naturahst, Professor P. Harting, at Utrecht, told me, after an exact inquiry, 'that this vegetable fragment issued from a leaf of the family Monocotyledon, probably not from a palm-tree, but from a Padanacege or Scitaminese—consequently, from trees belonging to the tropical regions. Now I am sure it comes from the tropics. I am greatly surprised to perceive that a piece of leaf of this dimension could run off a distance of more than 1200 geographical miles in the upper regions of the atmosphere; for the nearest coast-lines of the two continents, America and Africa, lay at the said distance from the place where this vegetable fragment was caught, by the carefulness of Capt. S. Stapert, one of the most zealous co-operators. There can be no doubt that it comes from South America, because the direction of the trade-winds on the west coast of Africa is too northerly to bring this fragment to the finding-place in 20° N. and 38° W."—Letter from Lieut. Andrau, of the Dutch Navy, dated Utrecht, Jan. 2, 1860.
