The mad dog incident, related in chapter 10, is one of the most memorable parts of the novel. Lee uses the literary technique of building suspense in order to pull off an exciting climax and a sudden, dramatic resolution.
Lee builds up the tension by revealing the the dog's madness only very gradually, as he first appears to the children's uncomprehending eyes. They tell Calpurnia that he is behaving strangely, and at first Calpurnia doesn't quite understand the seriousness of the situation either, until she sees the dog for herself. Then she is galvanized into action, ringing up people to warn them, bustling the children indoors. The reader gets a sense of the growing fear and alarm along with the children, as a tense situation develops before their eyes.
Imagery is a standard type of poetic device. There are several effective uses of imagery in this passage, such as the comparison Scout makes between the dog 'and a car stuck in a sand-bed'. This heightens the visual sense of the dog's erratic, lopsided carriage as he dawdles up the street. Another effective use of imagery is used in relation to Atticus, when he takes up the gun to shoot the dog. At this point he looks to Scout like an’ underwater swimmer’. This image emphasizes how the whole scene is so unbearably tense that Atticus’s movements take on an air of unreality as the incident heads towards the climax.
An example of sophisticated word choice is the word ‘vehemently’, used to describe Atticus’s reaction when Heck first asks him to shoot the dog, knowing that he has an extremely accurate aim. 'Vehemently' means to say or do something violently, or with great emotion. The use of this word shows just how pressurized Atticus feels by the whole situation, when he is called upon to eliminate the mad dog. He does not want to take on such a heavy responsibility because of the extreme risk involved; if he misses with the first shot there is every chance that the dog will charge. However, in the event, he executes his duty with an extraordinary degree of coolness, considering the danger. His courage, calmness, and skill in killing the dog with a single shot reveal him to be a true hero to his children, who formerly had doubted that he possessed any exceptional abilities.
An example of noteworthy punctuation appears in the following paragraph, as Scout looks down the deserted street that is awaiting the advent of the dog:
I heard Mr. Tate sniff, then blow his nose. I saw him shift his gun to the crook of his arm. I saw Miss Stephanie Crawford’s face framed in the glass window of her front door.
The regular use of full-stops here makes the sentences short and clipped, imitative of the way that the sights and sounds of the tense street impact upon Scout’s senses as she stands and waits along with the rest.