At 11 A.M. we started back for Waterville. We came by a different route than the one of yesterday, and passed through Guilford (had lunch here), Dover- Foxcroft (on the Piscataquis where Jackson reputed slate quarries, but no one now knows of their situation), Lexington, Cornish, Newport, Pittsfield, Burnham, Clinton, Benton (on trail collecting ground of two days ago) and then Waterville. Then fetched my box of rock which Raymond will ship from Cambridge. Finally at 5:15 visited the slate exposure along the Penobscot beneath the campus of Colby College. It was soon dark or that we had off a half hour of collecting, and got in that short time got a number of rocks. They are by no means as rare as I thought. Offered Perkins two dollars to get a student collecting for one. Raymond trotted along all the four Colby College tracks to read them up. I volunteered to write them for Raymond. The Boston Society is to publish the result.