13 Sep. 1805
I have this day viewed the canal from one end to the other. also the place where the Dam is to set. It is my opinion that a dam less than four feet high will not throw a sufficient quantity of water into the canal for three water wheels in consiquence of its extreem narroness great length & rough sides, all which tends to retard the motion of the water, I think that as we have a dam to make we had better raise it five feet high for several reasons. First that it will be more certain to supply the mills secondly that it will enable us to have larger wheels which will be a great advantage to the preservation of the gears which will be very subject to get wet by freshes & thirdly that should you be compelled to make Locks for boats to pass up and down the canal it will lessen the labour very much to make it wide enough for boats to pass—the method that I should take for building the dam is this Suppose the dam to be 12 feet thick lay a sill along on the rocks that now sew out of the water and bolt it down to the rock, then raise the wall in all vacant places up to the sill which will be a guide to face the wall by for the upright planking to bear against raise the lower wall up to a proper height to lay on a sill and fill in between the walls with the cast off stone up eaven with the sleepers which are dove tailed into the sills and pinned fast. plank the slope with inch or inch & quarter plank and at the top to pin on a plank 4 or 5 inches thick to prevent logs from breaking the edge of the plank. then level off the top nicely in order that the water may tumble over regularly from one end to the other, then the timbers will be always wet and will last along time
it may easily be made tight by fixing a tumbling body on the ferry boat and boat dirt from the banks and tumble in against the upright planking, a dam built on ths construction I think may be made tight and safe from being swept off by freshes and will also look handsome—I would hire the two young men that works with Mr. Hope to lay the stone in the lower wall of the Dam whilst the other hands are attending on them and filling in between the walls—
[GRAPHIC IN MANUSCRIPT]
MHi: Coolidge Collection.