Why does Jem cry at the end of chapter 7 in To Kill a Mockingbird?
Jem cries because Nathan Radley cements in the hole in the tree, eliminating their connection to Boo Radley.
At the beginning of the book, Jem and Scout just see Boo Radley as a curiosity and form of amusement. They can act out his life story, or be afraid to pass his house. Yet they soon come to understand that Boo is lonely, and try to make him come out. This results in a slow connection growing between them that develops in the form of presents left in the tree hollow on the edge of the Radley lawn.
Scout finds the first gift as she is walking by.
Some tinfoil was sticking in a knot-hole just above my eye level, winking at me in the afternoon sun. I stood on tiptoe, hastily looked around once more, reached into the hole, and withdrew two pieces of chewing gum minus their outer wrappers. (ch 4)
The gum is the first overture of friendship from Boo, even if Scout does not know it. When she doesn’t die, she enjoys the gum. The children find many other gifts there, including twine, a watch and a chain, a spelling medal, a rare penny, and soap dolls carved to look like them.
When the tree is cemented, Jem asks Mr. Nathan why. He says it was sick. Jem is aware of what really happened though. Nathan has closed Boo’s only connection to the outside world and friendship. That is why Jem cries. He pities Boo, and has come to think of him as a friend. Later, Boo makes other connections with them, but they always remember the little gifts.
In chapter 7, Jem and Scout decide to write a letter to the anonymous person leaving them gifts in the knothole of the Radley tree. However, when Jem goes to put the letter in the knothole, he discovers that it is filled in with cement. Confused and heartbroken, Jem waits to speak to Nathan Radley and finally gets his chance to talk to him the next day. When Jem asks Nathan why he put the cement in the knothole, Nathan tells him,
"Tree’s dying. You plug ‘em with cement when they’re sick. You ought to know that, Jem" (Lee, 64).
After hearing Nathan's response, Jem becomes suspicious of his explanation and decides to ask his father if the tree looks sick. After looking at the tree, Atticus tells his son, "That tree’s as healthy as you are, Jem" (Lee, 64). Scout then mentions that Jem stood on the porch and didn't come into the house until later that night. Interestingly, Scout notices from the streaks on Jem's face that he has been crying to himself.
The reason that Jem cries is because he realizes that Nathan lied to him. It seems he has begun to suspect that Boo Radley is the gift giver—and that Nathan is putting a stop to Boo's attempt to reach out. Nathan Radley's dishonesty and cruelty to Boo, as well as Jem's lost chance of communicating with Boo, are the reasons he cries by himself on the front porch.