Now, I do not hesitate to confess that the thermal condition of the North Pacific revealed by these observations, was altogether contrary to my anticipations. I had supposed that the virtual seclusion of its basin from the influence of Arctic cold, and the vast distance of its northern part from the Antarctic area, would have combined to give to its sea-bed a temperature above that of the other great ocean-bottoms. And no reason had occurred to me, why the surface-stratum should contain so small a measure of heat. And yet, on reasoning out the problem, I came to see that, anomalous as it may seem, the want of communication between the North Pacific and the Arctic basins, in the presence of a perfectly free communication with the Antarctic, is a reason why the upper stratum of the former should be rather colder than warmer. For we may consider the entire Pacific and Antarctic basin in the light of a long trough, at the south end of which Polar cold is applied to the surface; while Equatorial heat is applied to the surface at, say, one-third of the length of the trough from the north end. Now, in the southern division of the trough, the circulation will go on as in the former case (p. 4); the water chilled by Polar cold descending and flowing along the floor of the trough, and being replaced by the surface-inflow of warmer water from the Equatorial region. But as the Polar bottom-flow will not meet any similar flow from the opposite end of the trough, only a portion of it will rise to the surface under the Equator, the remainder continuing to flow to the northern end of the trough, thus keeping its temperature down nearly to the Antarctic standard. On the other hand, the South-Polar surface-indraught will not only extend to the Equator, but, in the absence of any corresponding indraught towards the North Pole, will act backwards (as it were) upon the upper stratum of the North Pacific, giving it a southward movement towards the Equator, instead of the northward movement from the Equator, which is so remarkable a feature of the North Atlantic. To replace this, the cold under-stratum of the North Pacific will be continually rising towards the surface; and thus the powerful action of the sun's summer heat between the parallels of 30° and 50°, will be constantly antagonized by that of the winter cold of the Antarctic area at a distance of eight thousand miles or more. But if a subsidence of the land bordering Behring's Strait were to take place to such an extent as to open a broad and deep channel between the North Pacific and the Arctic basin, the outflow of Polar water that would then go on from the latter into the former, would produce a movement of the upper stratum in the contrary direction; thus drawing a surface-flow of Equatorial water towards the Aleutian Islands, and raising the temperature of the land-border on either side.
Thus we see the great importance of this general oceanic circulation in regulating the distribution of temperature, alike at the surface and over the bottom, of those vast marine areas, which, in the aggregate, cover little less than three-fourths of the whole superficies of our globe. And it is by this distribution of temperature, that the distribution of animal life is mainly dominated. But as I showed on a former occasion (vol. xxii. p. 391), its influence in providing the inhabitants of the abyssal waters with both food and oxygen is not one whit less important; the condition of a deep inland sea (such as the Mediterranean), which is virtually cut off from its influence, being one of such stagnation, as to be incompatible with the existence of animal life at any great distance beneath the surface. There is no reason to suppose that animal life could exist on the ocean-bottom at depths far exceeding that of the barren sea-bed of the Mediterranean, if it were not for the vertical movement produced by opposition of temperature; which, by bringing up every drop of ocean-water, in its turn, from the deepest abysses to the surface, purifies it from the carbonic acid and other products of animal decomposition with which it has come to be charged, imparts to it a vivifying dose of oxygen, and mingles with it those products of vegetable life, which serve, when carried down to the ocean-depths, for the nutrition of the animals that swarm upon their bottom, and contribute, by the accumulation of their calcareous exuviæ, to form the components of future continents.
THE DILEMMA.
CHAPTER XXIV.
The residency at Mustaphabad, which was now to become the scene of an eventful episode in the history of the Great Mutiny, stood, as has already been explained, in a park of about fifty acres, sur-
