continually & continuously

问：附有汉译的Advanced Learner's ditionary把continually解释为"屡屡地，再三地，不断的"。又把continuously释为"连续不断地，不停歇地"。在下面两个空里各应填哪一个词才正确？
Ships cross the seas.
This water has been boiling for over an hour.

答：遇到这种情况，可以先看该词典的英文解释。该词典对continual的解释是：going on all the time without stopping, or with only breaks。而对于continually的解释则是again and
agian; without stopping。它对continuous的解释是going on without a break.根据这样的解释，再看看词典给的例句：Aren't you tired of this continual rain? 各continuous performance,1.00 p.m. to 11.30 p.m。这样做了，也许可以决定如何填空，例如：
Ships continually cross the sea.
This water has been boiling continuously for over an hour.
理由是：continually强调的是"一而再"，"络绎不绝"，而continuously强调则是毫无间歇。这与原句的含义是比较相符的。因为不能想像海上无时无刻有船在渡海，毫无停歇。也不能想像同一壶水一会儿沸滚，一会儿又停了下来。
也可能在这样做了之后仍然觉得无从选择，这时不妨查其他字典，例如有的词典就对continual的解释是：repeated;regular; frequent。对continuous的解释则是continuing without interruption;unbroke。例句是：
He hates these continual arguments with his wife.
The brain needs a continuous supply of blood.
如果这还不足以说明问题，还可以查阅同义词词典，或论述词的用法区别的词典。
但是，往往需要多次接触才能判定一个词的用法，如果指望每遇到一个生词就会用，那是不现实的。