The voyage around the world therefore served a double purpose.

因此，环球航行有双重目的。

He had a double purpose in accepting Clayton's offer.

他接受克莱顿的提议有双重目的。

I cannot sufficiently praise the skill with which this double purpose has been pursued.

我不能充分赞扬追求这一双重目的的技巧。

They were both wrapped in old and shabby outer garments, which might, perhaps, serve the double purpose of protecting their persons from the rain, and sheltering them from observation.

他们都裹着破旧的外衣，这也许有双重作用，既可以遮风挡雨，又可以避免被人看到。