In the United States the peninsula of Florida is an evidence of the land produced by the labor of the coral polyp. Florida has now ceased to increase toward the east, for on this side it touches the deep waters of the gulf, and the polyps can live only in shallow water. The peninsula increases only on its southern and western coasts. The cut at the end of this chapter represents the appearance of coral islands as they first rise to the surface, before the gathering soil provides the conditions for covering them with the luxuriant vegetation of the tropics.
The cut at the head of this chapter, of an aquarium, represents a new appliance of modern times, which is a most valuable aid in our obtaining a knowledge of the habits of the animals living in the sea. In fresh water, as well as in salt, the mutual relations of the vegetable and animal life serve to keep the water from becoming stagnant. The plants secrete the carbonic acid gas, which the animals give to the water by breathing, and in so doing free the oxygen which the animals require. In keeping therefore an aquarium, the desired point is to provide such a natural proportion of vegetable and animal life as shall preserve this balance. In many of the larger museums of Europe, large aquariums have been built, and an opportunity thus afforded for the study of the various animal forms, the habits of the vegetable growths, and their relations. Some of these structures are so arranged that they surround a room which receives its light only through the water in the aquaria, and thus the spectator, without disturbing the fish, can watch them feeding and performing all their actions.
From this arrangement of the aquaria, as the light passes from the water to the eye, the spectator is not disturbed in his vision, as he is by trying to look into the water from above, by the refraction of the light. A great deal that has been learned in modern times concerning the growth of the vegetation of the sea, of the habits of the animals, of their manner of life, their food and their growth, has been obtained from the chance of observation afforded by the various aquaria. Beside the positive benefits which have thus resulted from the public aquaria, those in smaller form afford for the lover of natural history a new and interesting way of carrying on his studies. In this way also the habits of observation are formed in the young, and it is fair to believe that the spirit of inquiry thus excited will tend to increase the knowledge of the phenomena of life, and its relations to the conditions of existence.
It has been by this course that the race itself has risen from barbarism to its present degree of civilization, and with the new appliances of modern times, it is evidently impossible to limit the probabilities of advance in the future.
A few facts about the extent of our commerce will show the difference of the spirit with which the ocean is regarded in modern times, compared with that prevailing in antiquity; and the different use we have learned to make of it, from the time when the exchanges of the world were confined to a few coasters, who hardly ventured out of the sight of land. To give even the most condensed summary of the world's commerce to-day would require a series of volumes; but a few figures taken from our own will enable the reader to judge of that which is now going on all over the world, uniting the most distantly separated nations; enabling them to become acquainted with each other; and impressing them with the fact that by industry alone are the material comforts of life to be attained, and that the task before humanity is to become acquainted with the products of the world, with the forces of which it is the theatre, and learn to control them for our own benefit.
From the report of the Bureau of Statistics, for a portion of 1873, we learn that the imports and exports of the United States during eight months, ending with February, 1873, amounted to the following totals: Imported in American vessels, $104,891,248; imported in foreign vessels, $317,043,490; imported in land vehicles, $12,356,325. During the same period the domestic exports in American vessels amounted to a total of $108,246,698; in foreign vessels, $311,816,048; and in land vehicles, $5,282,949. At the same time the re-exportation of foreign products amounted in American vessels to $5,147,805; in foreign vessels to $10,938,300; and in land vehicles to $1,693,795.
The number and tonnage of American and foreign vessels engaged in the foreign trade, which entered and cleared during the twelve months ending with February, 1873, was as follows: American vessels, 10,928, carrying 3,597,474 tons; foreign vessels, 19,220, carrying 7,622,416 tons. The report of the Bureau for 1872, gives the following totals of the number of vessels and their tonnage engaged in the commerce of the United States. Upon the Atlantic and Gulf coasts, 21,940 vessels carrying 2,916,001,058 tons. On the Western rivers, 1,476 vessels carrying 354,938,052 tons. On the Northern lakes 5,339 vessels, carrying 726,105,051 tons. On the Pacific coast, 1,094 vessels carrying 161,987,050.
From the port of New York alone there are now thirteen lines of steamships plying to Europe. Of these the Anchor line has 15 steamers, with a tonnage of 36,127 tons; the Baltic Lloyds has 4 vessels of 9,200 tons; the Cardiff (a Welsh) line has three vessels of 8,000 tons; the Cunard has 23 vessels of 59,308 tons; the Holland (direct) line has two vessels of 4,000 tons; the General Transatlantic (a French line) has 5 vessels of 17,000 tons; the Hamburg has 15 vessels of 45,000 tons; the Inman line has 12 vessels of 34,811; the Liverpool and Great Western line has 7 vessels of 23,573 tons; the North German line has 20 vessels of 60,000 tons; the National line has 12 vessels of 50,062 tons; the State line has 3 vessels of 7,500 tons; and the White Star line has 6 vessels of 23,064 tons. Beside these ships, the thirteen companies are building from 30 to 40 more steamers to meet the demand for freight.
The ocean has thus become almost a steam ferry; almost every day a steamer leaves for Europe. With this knowledge of how far we have progressed in becoming acquainted with the ocean, it will be well to consider for a moment how much still remains for us to explore. In the middle ages, and even down to modern times, the maps of the world represented all unknown lands as inhabited by monsters; but every voyage made by discoverers has contracted the limits of these fables, until they have finally about disappeared. Still at the North Pole and in the Antarctic regions areas extending over a space of 2,900,000 and 8,700,000 square miles, respectively, have been, up to this time, unvisited. The icebergs and mountains of ice have kept them from our accurate investigations. The difficulties of such a sea are well shown in the adjoining illustration.
Discoveries have also to be made in the interiors of Africa, Asia, South America and Australia before the civilized portions of the race can claim a complete knowledge of the earth, their common dwelling-place. Every year, however, the portions unexplored grow smaller and smaller, so that we are justified in believing that eventually the whole world will be known to us, from actual observation.