这两种结构是相对于分词的逻辑主语而言的，分词的逻辑主语有两种：一是悬垂分词的逻辑主语，其二是独立主格结构的逻辑主语。在悬垂结构中，分词的逻辑主语就是主句的主语，如果两者不能构成逻辑上的一致关系则该句结构是错误的.如：

Seen from the space, the earth looks like a blue ball. 从太空看起来，地球像个兰色的球体。

这个悬垂结构seen from the space = when the earth is seen, …

Laughing and chatting, the puples left school for home. 孩子们说说笑笑回家去了。

同上述结构一样，Laughing and chatting = the pupils were laughing and chatting, …

独立主格结构与悬垂结构不同的是独立结构有自己的主语。这个主语有名词或代词通格来表示，放于分词之前，与分词形成逻辑上的主谓关系。例如：

So many comrades being absent, the meeting had to be put off.

这么多同志都缺席了，所以会议只得延期。

We all went home, he remaining behind. 我们都回家了，只有他留在后面。

Weather permitting, we will go for an outing next week. 如果天气许可，我们下周去郊游。

The class (being) over, the teacher dismissed the students. 下课了，老师把学生打发走了。

The job done, we all went home. 工作完成之后，我们就都回家去了。

With the tree growning tall, we get more shade. 岁着树的不断长高，树阴也越来越浓密了。

Everything taken into consideration, this plan seems to be more  reasonable. 把一切考虑在 内，这个计划看起来可行。

They worked throughout the night with the lamp lighted. 他们挑灯夜战。

    悬垂结构中的分词短语，往往可以还原成一个状语从句

。（注意 ，状语从句的省略）且状语从句的主语一定与主句的主语一致，而独立主格结构也能还原为一个状语从句，但主从句的主语是不一致的。 

  ① 时间

Looking up suddenly, Robert saw a rainbow in the sky.

 ----

Hearing the news that her son was rescued, she felt greatly relieved

----

② 原因

Not knowing how to pronounce the word “plough”, the Frenchman looked it up  in a dictionary.

Considering the importance of the experiment, they checked the result again and again.

Living in a remote village, we rarely have visitors coming.

  ③ 条件

This same thing, happening in the peacetime, would be a great disaster.

Unless meeting with unexpected difficulties at the office today, I shall be home early tonight.

  ④ 让步

Walking and sleeping, he has the plan in his mind.

   ⑤ 结果

Their car was caught in the traffic jam, thus causing their delay.

We introduced a lot of advanced devices策略, thus saving much time and labor.

  ⑥ 目的

We held a meeting, marking the anniversary纪念 of his death.

  ⑦ 方式（也称做伴随）

They stood by the roadside, watching the parade.

They sat together, studying carefully the design of the new project.

。