through是從物體的上方通過
by 是從物體的旁邊通過
還有cross是從物體的中間通過
through 是通過某種途徑
He bought the antique vase through a dealer.
他通過一個商人買到這只古花瓶
He became rich through hard work.
他靠努力工作而致富.
through表示“以；通過；經(jīng)由”.如：
by 是通過某種方法
1.表示以一般的方法或方式.如：
No one in those days could live by writing poems.
（2）表示傳達、傳遞的方式或煤介.如：
How did you send the letter,by airmail or by ordinary mail?
I came back by bus.
我是乘公共汽車回來的.