Falls near Roisters Town
19th Jan 1806
The subject of navigation which occasioned the following thoughts would dispense with any apology for presuming to address them to you; but the thoughts, should they not come recommended by novelty & feasibility in the execution, will however stand in need of & receive your indulgence, when the motive which suggested this communication is understood to be a disinterested desire to throw in my mite towards the advancement of the national prosperity.—
In contemplating the counter-currents of Rivers, I have thought, that the facilities which they offer to navigating vessels upwards; might be considerably increased by imitating nature in those points which are the cause of counter-currents—For this purpose where the rivers run pretty nearly in right lines for any considerable distance, might not moles be projected from the banks at suitable distances, so as to catch part of the main current, thereby causing a counter-current? In order that boats might not have occasion to go round the points of these Moles & so run the risk of being drawn into the main current, a sufficient space for their passage might be contrived through the frame or coffer work of the Moles, near to the bank where the water is always the stillest—
Where nature by her own projections or moles causes counter-currents; should the former require securing against unavoidable decay, (as they do most generally except their basis & elevation be rock) & the latter increasing, it may be done by enclosing the projecting point of land in a Coffer dam & extending it as far as may be thought necessary into the bed of the river, & filling up the intermediate space between the point of land & the extremity of the Coffer dam with stones or rubbish, or soil well puddled, Where the points are very prominent & narrow, cuts might be made through them for the passage of boats, answering to those through the artificial moles & as near as possible to the general bearings of the banks—
It may be objected to these moles, that the intermediate spaces would soon become too shallow for navigation, by the deposits of sand, mud & trees, brought down by the main–current—The objection seems well founded & is formidable—To obviate it, instead of these Moles being stationary, might not the principles of Boat or Ship-building be applied to them; securing the stern to the Bank by ropes & the head towds the bed of the river by anchors—Thus, before any considerable swell is apprehended, the anchors might be hove & the Mole vessels drifted along side the bank—By this means, all the deposits which might be made in those rivers, which are only navigable at certain seasons, would be swept away. But these would be trifling, compared to what would be caused by the stationary Moles, because the greater part would drift under the Mole vessels, whenever a swell raised them from the bottom of the river—
I remain with profound respect your’s &c
MoSHi: Bixby Collection.