and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated.

测出回声间隔的时间，便可算出该处海洋的深度。

and beyond six or seven they are worthless.

如果超过六七天，天气预报就没有了任何价值。

This is a pity, because noise abatement really is a good cause.and it is likely to be discredited if it gets to be associated with bad science.

要求减少噪音确实是件好事，但是如果与拙劣的科学掺杂在一起的话，就不会被人们所信任，这是很遗憾的。

From the Skeppsbron and surrounding islands the people watched this thing of beauty begin to spread her sails and catch the wind.

人们从斯开波斯布朗和周围的岛屿前来观看这艘美丽的战船扬帆起航，乘风前进。

He was, above all, a man who experimented:

他首先是个实验工作者，

a wave length (the horizontal distance between two wave crests),

波长（两个浪峰间的水平距离）