第4章 THE BED OF THE ATLANTIC 大西洋的海床

(To be read before a Map.)

If the waters of the Atlantic could be drawn off, so as to expose to view the great trough which separates the Old World from the New, a scene would present itself of the grandest and most imposing character. The very ribs of the solid Earth, and the foundations of the hills, destitute of the garniture of vegetation, would be brought to light. We should have unrolled before us a vast panorama of mountains and valleys, of tablelands and plains, of deep gorges and lofty peaks, rivalling in grandeur and in variety the continents of the upper world.

Comparatively little is yet known of the bed of the South Atlantic; but the basin of the North Atlantic has been extensively surveyed by the English and American Navies. Let us suppose this vast basin to be emptied of its waters; and, with the aid of the charts which have been constructed, let us in imagination traverse these deep places of the Earth and learn what we can of their secrets. Remembering that what we have to explore is really a vast system of table-lands, mountains, and valleys, let us first endeavour to grasp its broad outstanding features.

In the northern part of the basin there stretches across the Atlantic from Newfoundland to Ireland a great submarine plain, known in recent years as Telegraph Plateau. About one hundred miles from the coast of Ireland this plateau, rising as a broad terrace, reaches to within a hundred fathoms of the surface of the ocean. On this terrace stand the British Islands, the climate of which is materially affected by their being thus removed from the influence of the colder waters in the depths of the Atlantic. About midway between these islands and Iceland, it has been found that icy cold water is constantly flowing towards the Equator, at a considerable depth beneath the surface, to supply the place of the warm surface-water moving northward from the Equator. At the depth of three-quarters of a mile, the temperature of this great polar current is two degrees below the freezing point. The British terrace raises these isles out of this cold stream, and thus none but the warmer upper waters flow around the British coasts.

From the middle of Telegraph Plateau an immense submarine continent, nearly as extensive as South America, stretches first southward and then towards the west, occupying the whole central area of the North Atlantic basin.

On either side of this central continent there is a broad and deep valley. These valleys converge as they go southward, and meet in mid-ocean between the Cape Verd and the West India Islands. Of these valleys, the western is much deeper than the eastern. Its deepest parts are found midway between the Bermudas and the Azores, and off the island of Porto Rico, where the sounding-line has been carried deeper than anywhere else in the ocean. It is the deepest part of the Atlantic.

Could we transport ourselves to that point, we should stand on what is perhaps the very lowest part of the Earth's crust. We should be at least five miles below the ordinary level of the sea, surrounded on all sides by great mountains. On the north the Bermudas would be seen as lofty mountain-peaks, rising half as high again as the summits of the Alps or the Andes. On the north-east we should see the Azores as the culminating points of the central continent. Pico, their highest point, would appear, from the general level, as a mountain 400 feet higher than Mont Blanc; but from our imaginary standpoint in the lowest depths of the Atlantic, it would be six and a half miles in height — a mile higher than the highest peak of the Himalaya, the loftiest mountain on the globe.

Each of these great ocean valleys rises in a series of terraces to the sides of the Old and New Worlds respectively. The course of the western valley, which lies off the United States and the West India Islands, has been traced as far south as to the Equator. The terraces of the eastern valley rise from the depths of the ocean to the western coasts of Europe and Africa. Off the coast of Africa they rise into a series of lofty and rugged summits, which we call Madeira, the Cape Verd, and the Canary Isles; and the whole system culminates in the Peak of Teneriffe in the last-named group. That peak is two miles and one-third above the level of the sea. The lowest point yet sounded in the bed of the Atlantic is five miles and a third below that level. The whole mountain system of the Atlantic basin, therefore, extends to upwards of seven miles in vertical height, or higher than any of the mountains of the globe are above the level of the sea.

By bringing up specimens from the depth of the Atlantic, and studying them under the microscope, it has been ascertained that the bed of the ocean is covered with very minute shells, which lie on the bottom as lightly as gossamer. The microscope has not detected a single particle of sand or gravel among these little mites of shells. This fact proves that quiet reigns in the depths of the sea: that as in the air ocean there is a region of perpetual calm, “above the clouds;” so in the ocean of waters there is a region where perpetual calm prevails, beneath the troubled waves. There is not motion enough to abrade these very delicate organisms, nor current enough to sweep them about, or to mix with them a grain of the finest sand.

It may be that the myriads of animalcules which make the sea glow with life are secreting from it solid matter which is destined to fill up the cavities below. They furnish the atoms of which mountains are formed and plains are spread out. Our marl-beds, the clay in our river-bottoms, large portions of many of the great basins of the Earth, even flinty rocks, are composed of the remains of just such minute animals as those which have been fished up from a depth of three miles below the sea-level. These creatures, therefore, when living, may have been preparing the ingredients for the fruitful soil of a land that some earthquake or upheaval, in ages far away in the future, may yet raise up from the bottom of the sea for the use of man.

Words

ascertained,found.

cavities,hollow places.

converge,draw near to each other.

culminating,crowning.

destined,appointed.

detected,discovered.

garniture,embellishment.

gossamer,cobweb.

ingredients,elements.

organisms,structures.

panorama,comprehensive view.

perpetual,constant.

separates,keeps apart.

submarine,under the sea.

summits,peaks.

surveyed,examined.

temperature,degree of heat.

transport,convey.

Questions

Of what does the bed of the ocean consist? What part of the Atlantic has been surveyed? By whom? What plain stretches across the northern part of the basin? On what do the British Isles stand? What effect has this on their climate? Why? What extends southward from the middle of Telegraph Plateau? What is there on either side of the central continent? Where is the deepest part of the Atlantic? If we could stand there, how far should we be below the sea-level? By what should we be surrounded? What would the Bermudas appear to be? And the Azores? Where does the whole Atlantic mountain system culminate? What is its extent in vertical height? With what is the bed of the ocean covered? What shows that quiet reigns in the depths of the sea? Of what are the animalcules found in the bed of the ocean the elements?

请参照地图阅读此文

如果大西洋的水可以被抽干，来显现出分隔开新世界与旧世界的一条巨大海槽，一幅宏伟壮观的景象会展现在我们面前。坚硬地球的山脊，山脉的形成，植被装饰的贫乏，会被一一发现。在我们面前展现出的是一幅巨大的关于山脉和山谷、高原和平原、深邃峡谷和巍峨山峰的全景，竞相展现着它们的宏伟和上层世界的多样性。

相比之下，人们对南大西洋的海床知之甚少。但英国和美国海军已经对北大西洋盆地进行了广泛勘测。我们可以假设这片广阔的盆地没有水，在已经构制的航海图的帮助下，我们的想象可以穿越这片地球上最深的海域，去了解我们可以得知的秘密。须谨记我们要探索的的确是一片广阔的高原、山脉和山谷，我们首先可以尝试的是，掌握它们众多的显著特征。

在这片盆地的北部区域，横跨大西洋，从纽芬兰岛到爱尔兰岛，绵延着一片宽广的海底盆地，近年来被称作“电报高原”。在距爱尔兰海岸大约100英里处，这片高原如一片宽广的梯田升起，一直到达距海面不足100英寸之内。不列颠群岛矗立其上，而不列颠群岛的气候深受这些梯田的影响，而免受大西洋底部冰冷海水的影响。大约在这些岛屿和冰岛的正中，人们发现寒冷的冰水在海面以下极深的深度，不停地向北流向赤道，供给这片区域温暖的海面水，向北部的赤道流淌。在大约四分之三英里的深度，水的温度低于冰点两度。不列颠梯田因为寒流升高影响到这些小岛，以致只有这种温暖的上层水流围绕不列颠海岸流淌。

一片几乎和南美洲一样广阔的巨大的海底陆地，从电报高原的中央首先向南延伸，之后向西，占据了北大西洋盆地的整个中心地区。

在中央陆地的周围，有宽广且深邃的山谷，它们向南部延伸时同时汇聚集，在佛得角和西印度群岛中央处聚于一处。这些山谷的东部比西部深得多。它最深的地方位于百慕大和亚速尔群岛之间，而在波多黎各岛的外围，攀升至比海洋中其他任何地方都更深的部位，这就是大西洋最深的地方。

如果我们能够到达这一点，我们即将位于地壳最低点，也就是在平均海洋高度下至少5英里处，且四周都包围着高山。在北部，百慕大是一片巍峨的山峰，高至如阿尔卑斯和安第斯山制高点一半的高度。在东北部，我们会看到亚速尔群岛是整个中央陆地的最高点。从海洋的一般高度出发，最高点皮科，相当于比勃朗峰还要高400英寸的山。而从我们想象中的站立点出发，在大西洋的最深处，它会有6.5英里高。这比全球最巍峨的山峰——喜马拉雅山的最高峰——还要高出一英里。

这些广阔的海洋山谷都沿梯田状分别攀升至新旧世界的边缘。西部山谷的攀升轨迹沿着美国和西印度群岛的外围，一直向南延伸至赤道。东部山谷的梯田从海底攀升，一直到欧洲和非洲的西海岸。在非洲海岸边缘，它们形成了巍峨崎岖的制高点，也就是马德拉、佛得角和加那利群岛。而这整个一片山谷达到特内里费峰这一最高点时，位于海平面的英里之上。而大西洋海床的最低点，在海平面之下英里处。因此大西洋盆地的整个山区在垂直高度向上延伸了7英里。或者可以说，这比地球上海平面之上的所有山峰都要高。

通过从大西洋底部采取的样本，并在显微镜下对它们进行的研究，我们能确定大西洋海床遍布了微小的贝壳。它们像游丝一样微小，停留在海洋底部。显微镜没有在这些贝壳中发现任何颗粒物或者砾石。由此可以得知，宁静统治了整个海洋底部，这里是一片如云端之上由宁静统治的区域。海水中，在汹涌的波涛之下，四处都笼罩着这种永久的宁静。没有任何动态能够腐蚀这些微妙的微生物，也没有任何波涛让它们随波逐流，或者任何细沙能够将它们混杂。

也许正是这无数的微生物使海洋变得生机盎然，而它们隐匿于那些注定要充斥着海底空洞的坚硬物质。它们提供了构成山脉和延展平原的原子。正是这些在海平面之下3英里处可以找到的微生物，构成了我们海床的泥灰，河流的黏土，还有地球广阔盆地的绝大份额，甚至是坚硬的岩石。因此当这些生物还有生命时，就已经做好了准备成为地球肥沃土壤的成分，在将来的许多年之后，甚至会引发地震或者地壳隆起。也正是它们，可能会从海洋底部升起，为人类所用。