This scene is rather tranquil, which means it is very peaceful and calm, such as when the poem says: "And beneath him, tranquil and broad and deep, Is the Mystic," this is describing the mystic as calm.
This scene shows defiance of the British, which means to not allow, or bold resistance. In the poem, an example is: "A cry of defiance and not of fear" This is read after the amercian forces fought and defeated the british, deying them.
The last scene here has a american in peril after a british guard has caught him doing something. Peril is having fear and panic, in the poem, it says : "In the hour of darkness and peril and need," which is talking about how frightened people were for the fate of the country.