有一读者问到：
(1)In his agitation at this discovery, he dropped his letter face downwards on the muddy pavement.
中的face downwards on the muddy pavement是不是独立结构？
face downwards是独立结构，on短语则是地点状语，修饰谓语动词dropped。独立结构face downwards也是修饰谓语动词dropped的状语，但表示结果。请注意这种独立结构由名词（即所谓独立主格）与副词构成，再如：
(2)I found we were going to win hands down . （hands down是独立结构）
(3)Moments later my child came head foremost into the world. （head foremost是独立结构）
(4)The boat was lying bottom upwards . （bottom upwards是独立结构）
(5)He stalked down the hillside, chin up and eyebrows down . （chin up与eyebrows down皆为独立结构）
