Why Half of Israel Stood on Mount Gerizim and Mount Ebal

"And half of them stood opposite Mount Ebal" (Joshua 8:30). What is meant by "and half"? Rav Kahana said: just as they were divided here, so they were divided over the stones of the ephod (this is written in remez 861). They raised an objection: there were two precious stones, and so forth, down to: this refutes Rav Kahana. Rather, what is meant by "and half"? It is taught: the half belonging to Mount Gerizim was greater than the half belonging to Mount Ebal, because Levi was below. The objection is raised: on the contrary, since Levi was below, they were fewer! This is what it means: even though Levi was below, the sons of Joseph were with them, as it says, "And the sons of Joseph spoke to Joshua" (and so forth). It is taught: Rabbi says: it is impossible to say that Levi was below, since it already says above; and it is impossible to say that Levi was above, since it already says below. How then? The elders of the priesthood and Levites were below, and the rest were above. Rabbi Yoshiyah says: anyone fit for the service was below, and the rest were above. Rabbi says: both these and those were standing below; they turned their faces toward Mount Gerizim and opened with the blessing, then toward Mount Ebal and opened with the curse. And what is the meaning of "upon" ["al"]? "Upon" means near. As it is taught: "And you shall place upon the row pure frankincense" (Leviticus 24:7) - Rabbi says: "upon" means near. Or does it not mean literally upon it? When it says, "And you shall cover upon the ark the veil" (Exodus 40:21), you must say that "upon" means near.