Whilst these “rivers in the ocean” are flowing more or less rapidly toward the Arctic regions, there are undercurrents moving slowly but irresistibly toward the equator, or at least in a direction to restore the equilibrium of waters. That these undercurrents come from the poles is already demonstrated by the thermometer. At certain depths under the equator the temperature is as low as 35° or 36° F. This low temperature could not be maintained unless supplied from the Polar regions. Fresh water freezes at 32° and salt water, that is sea water, at about 27°, according to the density. In many places north of England, Dr. Carpenter found the lower depths at a temperature of about 29°. He speaks of an ocean river 2,000 feet deep, colder than the freezing point of fresh water. Why could not this low temperature be maintained without supposing a supply from the Polar regions? The temperature of the earth’s crust twenty or thirty feet from the surface is quite uniform at 50° to 55° all over the temperate zones. At that depth—say thirty feet—it is not deep enough to be influenced by “the internal heat” of the earth, which we experience in going down into mines, or which shows itself in the hot water from very deep springs, and yet it is sufficiently covered so as not to be influenced by seasonable changes. The water would naturally take the temperature of the earth’s crust. This has been proven in the case of the Mediterranean Sea. This body of water is shut off from the general circulatory system by the Strait of Gibraltar, which is so shallow at its outlet that no communication between the deep water of the Mediterranean and the Atlantic can possibly take place. This great “middle earth sea” is at some places 11,000 to 12,000 feet deep. And yet Dr. Carpenter found the temperature in August and September 78° at the surface; and by going down with the thermometer the heat gradually diminished, until at the depth of 600 feet the temperature was 55°. From this point, curious as it may appear, there was no change in heat until the bottom was reached. Whatever was the temperature at 600 feet it was the same all the way down. He then ascertained that the temperature of the earth’s crust in that region was 54° and 55°.
This shows pretty clearly that depth of water alone does not produce the coldness found in the seas having connection with the Polar regions.
But there are other ways of demonstrating this lower cold current. At a meeting of the Geographical Society Dr. Carpenter exhibited in a simple and minute way these warm and cold currents. He had a trough constructed with plate glass sides, about six feet long, a foot deep, and the sides not more than one inch from each other. At one end of this trough a piece of ice was wedged in between the two sides. That represented the Polar area. At the other end heat was applied by a bar of metal laid on the upper surface of the water, and the end carried over the trough and heated with a spirit lamp—to represent the equatorial area. Then some coloring matter was put in the water; red at the warm end, and blue at the cold end. Now what took place? The water tinged with blue, put in at the surface of the Polar area, being subject to a cold atmospheric temperature immediately fell to the bottom. It then crept slowly along the bottom of the trough, and at the warm end it gradually rose toward the surface, and gradually returned along the surface to the point from which it started. The red followed the same course as the blue, but started from a different point. It crept along the surface from the Equatorial to the Polar end, and there fell to the bottom, just as the blue had done, and formed another stratum, creeping along the bottom and coming again to the surface. Each color made a distinct circulation during the half hour that the experiment was under observation.
Now this is an experiment that can be repeated in our parlors without going down to the Equator or up to the North pole; an additional proof that we often have the very thing at our doors that we travel thousands of miles to find.
Until the last four or five years the opinion prevailed that the ocean was barren of life at great depths. Continued researches, however, find that many forms and great profusion of life exists at a depth of two and three miles. This deep water life seems to be adapted to the low temperature near the freezing point of fresh water—and the forms are usually very small, requiring thousands to weigh a grain. There is an exuberance of that small animal known as globagerina—the little animal that secretes carbonate of lime for a covering, and makes pretty much all our chalk beds. The well known “White Cliffs of England” were made by this little animal, and in the deeper portions of the Atlantic it is still at work. Some day when the ocean’s bed is raised a few thousand feet these beds of chalk will appear and be exactly like the chalk of the cretaceous period, so much talked of and written about by geologists. Again, there are other animals dredged lately in larger quantities at a great depth, 3,000 and 4,000 feet, belonging to the sponges. These are busy in making flints—or such material as flints are composed of.
So we find in this large aquarium, the great sea, the same processes going on—the same material manufactured that took place in what is termed the older geological formation. Can we say that creation is complete? That the earth is finished, and, like a ship we read about the other day, to be disposed of for the old iron it contains? Not long since I visited a marble quarry, from which very curious and beautiful marble, resembling the onyx, was being taken. There were thick strata cropping out; and the air, and rain, and frost had disintegrated the exposed parts, so they looked as old as the earth. But just beneath, and in various places, were little springs of warm water, and as these bubbled out of the earth they deposited on cooling and exposure to the air, the same kind of marble—and there I saw going on the process of marble making that had continued doubtless for thousands of years.
On the shores, in the tide, pools and lagoons of Monterey bay we often gather little plants classed with the Algæ, or sea-moss, which we call diatoms. They are exceedingly small—some of them—so that we have to magnify them with the microscope several hundred diameters, in order to see how they are formed. Some kinds grow on the larger sea weeds, some on the rocks, and some appear to be free in the water, coming ashore in large quantities with the foam of the surf, and giving a greenish brown color to the sand of the shore. These diatoms are composed mainly of silex—flint. If we examine the rocks of our highest ridges and mountains and the cliffs of our shores in places, with the microscope, we shall find them largely composed of fragments of diatoms and spiculæ of sponges. And these are chiefly of the same species that we find alive to-day. Thus while the “chalk rocks” on our shores, the sand stones and harder rocks are melting away under the pounding waves of the sea, and being carried to the lower bottoms, fresh supplies of diatoms and sponges are mixed therewith, and we have a continuation, under our eyes, of what was begun thousands of years ago.
Let us for a moment consider this fluid we call water, especially sea water. Chemically speaking, pure water is one of the rarest things—that is, water absolutely free from all foreign matter, divested of everything save hydrogen and oxygen in the combining proportions, by weight one part of hydrogen to eight of oxygen; by volume, two of hydrogen to one of oxygen, we have pure water—an oxide of hydrogen. But absolutely pure water must be prepared in a vacuum, and it must never have contact with air of any kind. Pure water would be instantly fatal to any animal that had to breathe it with gills, as a fish, simply because it contains no oxygen in solution, which the animal can use to oxydize the blood in the gills. We in breathing air get oxygen by decomposing the air, but animals that breathe in water do not decompose the water, but take from it the free oxygen that is found mechanically mixed with the water. Pure water, being the standard of measurement of liquors and solids, is taken as one or one thousand. Sea water is 1,020, or near, whilst the water of the Dead Sea, or of lakes and seas with no outlet go as high as 1,225, or even to a point where they are saturated, or can not dissolve any more. Such is the case with the Great Salt Lake of Utah, and Mono Lake, of California. Water of this kind is not usually inhabited by any kind of gill breathing animals.
How did the sea become salt? By the washings out of the land, and the disintegration of the rocks by the elements, such as ice, wind, heat, rain, etc. The sun causes evaporation; so that the sea is being constantly lifted into the air and carried in the shape of clouds to the land, where it is drawn down and flows again into the sea. The solid matter carried down to the sea does not return. It remains in solution, or is deposited on the bottom. The clouds contain almost pure water. They distribute the visible ocean throughout the invisible air. The rocks and the trees, the animals and the air all receive their respective shares of water; and in the course of time it is returned to the sea. Were evaporation to continue at the present rate, it would require about 1,600 years before the ocean beds would become dry land. But in one way and another there is just as much water returned to the sea each year as is taken out. Not one drop is lost. The seas may change their beds—they may flow where the forest now stands, and their waters may cover our highest mountains, and their bottoms may rise many hundred feet above their present level, and still there will not be one drop more or less of the great body of water that now covers more than two-thirds of the earth’s surface. The sea will still claim its own. The water that floats to-day in the clouds may to-morrow course through some giant tree of the forest, or be taken up in forming a beautiful crystal, or aid in the bloom and fragrance of a flower, or be taken into the lungs of some animal and deprived of the oxygen that it holds in solution, or it may be converted into steam and propel a ship or a railroad train, or it may be buried under the earth in a bed of coal and only be set free some thousands of years hence. But like a wayward child it will return again to its mother—the sea.
“Tho’ the mills of God grind slowly,