1.Go by the common and the Highwood, and back by the watermill and the river.That will show how fast he can go.
"by" 在此处作介词，在词句中指“经过、经由”。介绍John的遛马路线，去时经过公共草地和乔木丛，然后从水磨和河边再回来。意思是这样溜达一圈，测测马儿的实力如何。
"by" 作为介绍还有两个意思：
①“在什么旁边，接近”：Judith was sitting in a rocking-chair by the window.
②“某处停留”：We had made arrangement to stop by her house in Pacific Grove.
2.He was very particular in adjusting the straps. He wanted to fit my head comfortably.
"particular"在此处指“讲究的，挑剔的”。文中是说John非常仔细耐心地为我调整皮带，只为了我的脑袋舒服一点。
"be particular about sth/doing sth"：对…挑剔。
3.When we were on the common, he gave me a light touch with his whip, and we had a splendid run.
"gave me a light touch"：在此处译为“轻轻地抽了我一下”
"splendid"：极好的
4.They stopped, John jumped off.
"jump off"：在此处是跳下来的意思
它还有“开始、出发”意思：The attack will jump off at dawn.
5.Also there were some people shooting rabbits near the Highwood, and a gun went off close by. He pulled up a little and looked, but did not move a step to right or left.
"go off"：在这里指 (枪)被发射；突然发出声响
"close by"：副词，在附近
"pull up"：在这里指 (使)…停住
6.It's my opinion that he has not been frightened or ill-used while he was young.
"ill-use"：虐待
7."He is exactly what John said", he replied, "a friendly creature I never wish to mount …"
"never wish to do"：从未想过
8.When he brushed my head, he went careful over my eyes as if they were his own, and never made me angry.
"as if"：好像
9.She did her work honestly, and did her full share.
"share"：这里指 “应做的、应承担的”
"do one's full share"：某人做了自己该做的那部分
10.After we had been out two or three times together, we grew quite friendly, which made me feel very much at home.
"be/feel at home"：固定短语，(想在家一样)舒适自在，无拘无束
另一种意思是 “驾轻就熟，运用自如”，后面通常接"with"：
Practice using the video until you feel quite at home with it.
11.The freedom to do what we liked was so pleasant.
"the freedom to do what we liked"：做我们喜欢的事的自由
12.We ran, lay down, rolled over on our backs, and ate a little of the sweet grass.
"on" 在这里作介词，表示“(身体重量)由(某部分)支撑”
在这里"rolled over on our backs"就是打滚的意思，因为要用背部去支撑自己的身体，所以用"on".
又比如：
The baby girl was on her hands and knees in the bathroom.
小女孩趴在浴室的地上。
13.关于 "lie" 和 "lay"：
lie lying lay lain 躺下；位于
lie lying lied lied 撒谎
lay laying laid laid 放置；下蛋
