In Chapter 1 of "To Kill a Mockingbird", in what way is Jem's description of Boo Radley "reasonable"? On what evidence is Jem basing it?
Jem's description of Boo Radley is only reasonable from the point of view of children whose sole knowledge about the recluse stems from the wild stories they have heard about him. Jem bases his information on some tracks he has seen "in their back yard many a mornin'", and from there his imagination takes over. Jem says that
"Boo (is) about six-and-a-half feet tall, judging from his tracks; he dine(s) on raw squirrels and any cats he (can) catch, that's why his hands (are) bloodstained - if you ate an animal raw, you (can) never wash the blood off...there (is) a long jagged scar that (runs) across his face; what teeth he (has) (are) yellow and rotten; his eye (pop), and he drool(s) most of the time".
According to Jem's description, Boo Radley must bear a startling resemblence to Frankenstein's famed monster. Although Scout does remember Boo's father as "a thin leathery man with colorless eyes, so colorless they did not reflect light", the ghastly details which Jem attributes to Boo's appearance have no basis in reality at all. The children have never actually seen Boo Radley, and all they know about him comes from gossip spread by neighbors who do not know him either. Jem's description of Boo really is not reasonable, but taken in the context in which it is developed, it is understandable that he should have such a fantastic impression of what his reclusive neighbor must look like (Chapter 1).