一百年前，我们对海洋的认知仅限于海面的二维形态，以及近岸浅水区深度参差不齐所带来的航行危险。
Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land.
辽阔的大海深邃而神秘，凡是偶尔想到海洋深处的人，大概都会认为海床是平坦的。
The open sea was deep and mysterious, and anyone who gave more than a passing thought to the bottom confines of the oceans probably assumed that the sea-bed was flat.
詹姆斯·克拉克·罗斯爵士于1839年已测出逾2400英寻的海深，但直到1869年，英国皇家军舰"豪猪号"奉命供皇家学会使用进行数次巡航考察，才在大西洋获得了一系列深海测深数据，并首次通过拖网作业采集到海底样本。
Sir James Clark Ross had obtained a sounding of over 2,400 fathoms in 1839, but it was not until 1869, when H.M.S. Porcupine was put at the disposal of the Royal Society for several cruises that a series of deep soundings was obtained in the Atlantic and the first samples were collected by dredging the bottom.
此后不久，著名的英国皇家军舰"挑战者号"探险队将海底研究确立为一门值得最杰出的物理学家和地质学家深入探究的学科。
Shortly after this the famous H.M.S. Challenger expedition established the study of the sea-floor as a subject worthy of the most qualified physicists and geologists.
随后一阵与铺设海底电缆相关的繁忙活动，很快就证实了"挑战者号"的观测结论——海洋许多区域的深度达两至三英里，并且水下存在规模相当可观的地形地貌。
A burst of activity associated with the laying of submarine cables soon confirmed the Challenger's observation that many parts of the ocean were two to three miles deep, and the existence of underwater features of considerable magnitude.
如今，现有的测深数据已经足够，可以绘制出大西洋的地形图，我们也对海床地形的丰富多样有了一定的了解。
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.
由于海洋覆盖了地球表面的大部分，因此完全有理由将海底视为地壳的基本形态，而大陆——连同海洋中的岛屿及其他地貌——则是叠加其上的次生构造。
Since the sea covers the greater part of the earth's surface, it is quite reasonable to regard the sea floor as the basic form of the crust of the earth, with superimposed upon it the continents, together with the islands and other features of the oceans.
大陆形成了起伏崎岖的高原地块，其海拔比开阔大洋的洋底几乎高出三英里。
The continents form rugged tablelands which stand nearly three miles above the floor of the open ocean.
从海岸线向外延伸，在距离几英里至数百英里不等的范围内，有一片坡度平缓的大陆架，从地质学角度看，它属于大陆的一部分。
From the shore line, out to a distance which may be anywhere from a few miles to a few hundred miles, runs the gentle slope of the continental shelf, geologically part of the continents.
大陆与大洋之间真正的分界线，出现在一段更陡峭的斜坡脚下。
The real dividing line between continents and oceans occurs at the foot of a steeper slope.
这段大陆坡通常始于约100英寻深度附近的某处，经过数百英里的水平距离，最终抵达真正的洋底——深度为2500至3500英寻。
This continental slope usually starts at a place somewhere near the 100-fathom mark and in the course of a few hundred miles reaches the true ocean floor at 2,500-3,500 fathoms.
这段斜坡的平均坡度约为1:30，但其中包含陡峭、甚至可能垂直的悬崖，以及平缓的覆有沉积物的阶地；在其下部，有一段漫长的渐缓收尾，这几乎可以确定是大量物质被侵蚀后从大陆体中被搬运至深水区所沉积的结果。
The slope averages about 1 in 30, but contains steep, probably vertical, cliffs, and gentle sediment-covered terraces, and near its lower reaches there is a long tailing-off which is almost certainly the result of material transported out to deep water after being eroded from the continental masses.