Tuesday 18th. Thermometer at [ ] in the Morning—[ ] at Noon and [ ] at Night.
After an early breakfast at Mr. Fairfax’s, Govr. Johnson & I set out for the Falls (accompanied by Mr. Fairfax) where we met the other Directors and Colo. Gilpin in the operation of levelling the ground for the proposed cut or Canal from the place where it is proposed to take the Water out, to the other where it will be let into the river again. In the highest of which, and for near 70 rod, it is between five & Seven feet higher than the Surface of the water at the head. After which it descends, & for at least 300 yards at the lower end, rapidly. This Cut, upon the whole, does not appear to be attended with more difficulty than was apprehended, for tho’ the ground is higher than was expected—it appears from some experiments of sticking a spiked stake down in those parts, that there is two or 3 feet of soft earth at Top, & the lower end of the Canal well calculated to receive locks to advantage; as also to dam the water, to throw it back into the Canal, & thereby reduce the digging—wch. may also be done at the head by loose Stones being thrown into the River to a Rocky Island. The length of the Cut, from the work of to day, is found to be about 2400 yards—a little more or less—upon exact measurement.
Took a view of the River from the Spout, or Cateract to the proposed entrance of the Canal below, to see if I could discover (as some supposed there was) the advantage of a Canal on the Maryland side in preference to one on this, but saw no likely appearances of it. About 400 yds. below the Cateract, there is a Cove into which emptys a small part of the river, thro deep & steep rocks on both sides which is a good defence to it, and some little distance below this again, is another Cove, but how a Canal was to be brought thither, I could not (having the river between) discover. However, at, & below both, is rapid water—one little, if any, inferior to the Spout at Shanondoah.
Having taken a rough level of the proposed cut, formed general ideas for the Canal—determined to go on with it this winter, as soon as our operations on the water, on acct. of the Season must cease—& come to some resolutions respecting the hireg. of Negros, we broke up, after dark & I returned to Mr. Fairfax’s.
The lock canal around the Great Falls became the major project of the Potowmack Company. Completed in 1802 with five locks, it was the most ambitious civil engineering project in America in the eighteenth century (see BROWN  description begins Alexander Crosby Brown. “America’s Greatest Eighteenth Century Engineering Achievement.” Virginia Cavalcade 12 (Spring 1963): 40–47. description ends ).