1、of which是引导一个定语从句，且引导词在句中做主语，先行词是high cliffs，of which表示与先行词之间的所属关系(通俗说就是"先行词"的......)。

如果还难以理解，那就把先行词代入which那个地方去理解，可能比较容易，可以看看例子。

例如：He has a lot of story-books, a few of which I have never read. 

(先行词是story-books，a few of which理解为a few of story-books“故事书”的几本，加以修饰就可以说成几本故事书)

2、outline...against...不是固定搭配，这个是联系上下文语境意思。

only their silhouettes were outlined（against the faintly glimmering sky）.

括号内是方式状语，说明outline所用的方式 。

against：以…为背景；衬托；相映；对照

silhouettes were outlined against the faintly glimmering sky.

轮廓以微光闪烁的天空为背景被勾勒出来。(因为这样翻译有些啰嗦，所以很多翻译是缩译了，就没有把"以...为背景"这几个字体现出来。)

3、没省略。

从句：What we could make out in the dusk, though, was amazing—high up the cliff ,thousands of hundred feet above the water

what引导一个主语从句。What we could make out in the dusk是从句主语；was是系动词；amazing是形容词做表语；从“—”就可以知道破折号后面是补充说明的成分啦。)

主句：主语从句+was a cluster of houses on stilts

(此处的主语就是前面那个主语从句；was是系动词；houses是表语；a cluster of是houses的修饰词；on stilts是状语)

4、So(连词)the place(主语)，besides being attractive(插入语), provided(谓语)distractions(宾语).

因此，这个地方除了吸引人之外，还让人分心。

being attractive这里是用到非谓语动词，它的逻辑主语是the place所以用ing形式。

(关于非谓语动词的知识点你可以上网查一下，因为非谓语动词是重难点，一时半会没办法说完)