Read it through once

'Bixby, you'll have to look out for President's Island and all that country clear away up above the Old Hen and Chickens. The banks are caving and the shape of the shores changing like everything. Why, you wouldn't know the point above 40. You can go up inside the old sycamore-snag, now.{footnote [1. It may not be necessary, but still it can do no harm to explain that 'inside' means between the snag and the shore.--M.T.]}