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新概念英语第四册课文原文：蝙蝠

111. So was born the echo-sounding apparatus, now in general use in ships.

这样就产生了目前各种船舶上普遍应用的回声探测仪。

112. Every solid object will reflect a sound, varying according to the size and nature of the object.

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。

113. A shoal of fish will do this.

鱼群也反射声音。

114. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish.

从测定海深到测定鱼群，这一进展比较容易。

115. With experience, and with improved apparatus,

根据经验和改进了的仪器，

116. 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.

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。

117. It has been found that certain bats emit squeaks and by receiving the echoes,

人们发现，某些蝙蝠能发出尖叫声，并能通过回声

118. they can locate and steer clear of obstacles -- or locate flying insects on which they feed.

来确定并躲开障碍物，或找到它们赖以为生的昆虫。

119. This echo-location in bats is often compared with radar, the principle of which is similar.

蝙蝠这种回声定位常常可与雷达相比较，其原理是相似的。