One if by land, two if by sea

Tonight I was reading Paul Revere's Ride to the girls.  In the later section of the poem where it describes where Paul revere is at 1 o clock, and then two o clock, Evelyn was perplexed.

E:  But it's all dark!

Me:  Yes, that's because it's 2 o clock in the morning.

(......pause.....)

E:  Hmmm..... I don't think he got very much sleep!