how does scrooges encounter with the ghost of christmas past compare to the ghost of christmas present

The Ghost of Christmas Past shows Scrooge the errors of his ways, but the ghost is not unkind to him. Rather, it simply and gently presents the visions of the past that help Scrooge realize that he must change his ways. The Ghost of Christmas Present is the second spirit to visit Scrooge.

Basically this is the difference:

For Primary Epic

No single author (each is a product of the oral tradition)Written down after centuries of oral transmissionSecondary Epic A single, gifted poet such as Virgil or Milton composes a work that imitates a folk epic. The Æneid and Paradise Lost, for example, involved considerable research and have the style of earlier epics (particularly in setting, dignified speeches, and extended similes.