Our knowledge of the sea a hundred years ago was confined to the two-dimensional shape of the sea surface and hazards of navigation presented by the irregularities in the depth of the shallow water close to the land.100年前我们只知道海洋是二维平面形的，及靠近陆地浅水区的深浅不一给航行带来危险。

The open sea was deep and mysterious,anyone who gave a passing thought to the bottom confines of the ocean probably assumed that the sea bed was flat.无边无际的海洋深邃而又神秘，凡是想过大海海底的人大概认为海底是平坦的。

Shortly after this (此后不久) the famous expedition (那次著名的考察)established a study of the sea-floor as a subject worthy of the most qualified physicists and geologists.把对海底的研究确立为一个值得一流物理学家和地质学家从事的研究课题。

A burst of activity associated with the laying of the submarine cables soon confirmed the "Challenge "'s observation that many parts of the ocean were 2 to 3 miles deep, and the existence of underwear features of considerable magnitude.铺设海底电缆的热潮很快证实了挑战者号的观察结果，海洋中很多地方深达两三英里，水下特征差异极大。

Today, enough soundings are available to enable a relief map of the Atlantic to be drawn and we know something of the great variety of the sea-bed's topography.现在已有足够的水深测量数据来绘制大西洋洋底的地形图，而且我们对海底地形的千变万化也有了一定的了解。

Since the ocean covers a great part of the earth's surface, it is quite reasonable to regard the sea floor as the basic form of a curst of the earth, with superimposed upon it, the continents, together with the islands and other features of the oceans.既然海洋覆盖了地球大部分表面，因此完全有理由把海床作为地壳的基本形式，上面附加着大陆、岛屿及海洋的其他的形态。

The continents form rugged tablelands which stand nearly 3miles above the floor of the open sea. From the shore line, out to a distance of somewhere from a few miles to a few hundred miles, runs the gentle slope of the continent shelf, geologically part of the continent. The real dividing line between continents and oceans occurs at the foot of the steeper slope.大陆是崎岖不平的高地，高出辽阔海洋海底近三英里。从海岸线向大海延伸几英里到几百英里的区域是大陆架的慢坡，从地质学上来说，它是大陆的一部分。大陆和海洋的真正分界线是在陡坡脚下。