Theory:

     Sid said: “Tom! Say, Tom!” [No response.] “Here, TOM! What is the matter, Tom? And he shook him and looked in his face anxiously. Tom moaned out: “Oh, don’t, Sid. Don’t shake me.” “Why, what’s the matter, Tom? I must call auntie.” “No-------never mind. It’ll be over by and by, maybe. Don’t call anybody.”
     “But I must! Don’t groan so, Tom, it’s awful. How long you been this way?” “Hours. Ouch! Oh, don’t stir so, Sid, you’ll kill me.”
     “Tom, why didn’t you wake me sooner? Oh, Tom, DON’T! It makes my flesh crawl to hear you. What is the matter?”
     “I forgive you for everything, Sid. [Groan.] Everything you’ve ever done to me. When I’m gone--------”
     “Oh, Tom, you aren’t dying, are you? Don’t Tom-------------oh, don’t. Maybe------------“
     “I forgive everybody, Sid. [Groan.] Tell'em so, Sid. And Sid, you give my window sash and my cat with one eye to that new girl that’s come to town, and tell her-------”
Explanation:
 
Sid asked Tom what the matter was?  Sid is Tom's half brother, and he went near him and was keen on understanding what happened to Tom. Tom asked Sid not to shake him. Sid was worried if he needs to call aunt. Tom said that he would wait for some time, maybe his agony will reduce.
 
The sound made by Tom petrified Sid, and he asked him to stop and tell him till how long he was in pain? Tom replied for hours together, and not to make any movement as it is very painful.
 
Sid insisted that Tom should have waken him much earlier instead of suffering by himself.
 
Tom continued saying that he had forgiven Sid for all the mistakes he has done as he is going to die.
 
Sid was terrified as he felt something happened to Tom, and he is going to die.
 
Tom further advised Sid, to give away his window glass and his cat which had only one eye, to the new girl in the town.
 
Meanings of difficult words:
 
Numbers
Word
Meanings
1.
Shook
Keen on.
2.
Anxiously
A feeling of worry.
3.
Window sash Part of the window that holds the glass and the framework.
Reference:
State Council of Educational Research and Training (2018). Term-1 English Standard-7. On Monday morning - Adapted from The Adventures of Tom Sawyer by Mark Twain (pp. 18-21). Published by the Tamil Nadu Textbook and Educational Services Corporation.