At a quarter of a mile from the point at which the highway issued from between the banks was a stone post, marking the spot where three roads met and united in one.

(1) on the banks ならばそれもありでしょう。しかしbetween the banksでもそれで大丈夫ですか、柴田さん？

(2) the highyay はthree roadsのうちの一本か否か？