Bat 2（蝙蝠）

So was born the echo-sounding apparatus, now in general use in ships. Every solid object will reflect a sound, varying according to the size and nature of the object. A shoal of fish will do this. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish. With experience, and with improved apparatus, it is now possible not only to locate a shoal but to tell if it is herring, cod, or other well-known fish, by the pattern of its echo.
这样就产生了目前各种船舶上普遍应用的回声探测仪。任何固体者反射声音，反射的声音因物体的大小和性质的不同而不同。鱼群也反射声音。从测定海深到测定鱼群，这一进展比较容易。根据经验和改进了的仪器，不仅能够确定鱼群的位置，而且可以根据鱼群回声的特点分辨出是鲱鱼、鳕鱼，这是人们所熟悉的其他鱼。

It has been found that certain bats emit squeaks and by receiving the echoes, they can locate and steer clear of obstacles -- or locate flying insects on which they feed. This echo-location in bats is often compared with radar, the principle of which is similar.
人们发现，某些蝙蝠能发出尖叫声，并能通过回声来确定并躲开障碍物，或找到它们赖以为生的昆虫。蝙蝠这种回声定位常常可与雷达相比较，其原理是相似的。

New words and expressions生词和短语

apparatus
n. 收到
shoal
n. 仪器
herring
n. 鱼群
cod
n. 鳕鱼
squeak
n. 尖叫声