In "Macbeth", what predictions do the witches make about Banquo?

The first and only time
the Weird Sisters interact with , they tell him,

Thou
shalt get kings, though thou be none.  (1.3.68)

In other
words, then, Banquo will never be king himself -- aswill -- but those in his line of descendants
will be kings.  In this way, he is lesser thanbecause he will never be king, but he is also
greater than Macbeth because he will sire children who will sire children who will be kings. 
His line will live on, though Macbeth's will die.  Banquo will not be as happy as Macbeth
because he will not rule himself.  However, he will be happier than Macbeth for the same reason
that he will be greater.

Though Banquo never again interacts with the Weird
Sisters, they do provide yet another prophecy regarding Banquo when Macbeth visits them a second
time.  Macbeth asks if Banquo's "issue [will] ever / Reign in this kingdom"
(4.1.108). answer him by showing him a line of eight kings, the last one holding a mirror.  Each
of these eight kings bears some physical resemblance to Banquo, and then, finally, the ghost of
Banquo, bloodied from his murder, smiles at Macbeth and "points at them for his"
(4.1.129).  The mirror held by the last one seems to signify that Banquo's line will go on and
on.