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Moore, Thomas
Autograph Letter Signed, Brookeville Maryland, 5th Month 22, 1815, to Cadwalader Evans, Jr., Philadelphia, Pennsylvania

folio, 4 pages, possibly a retained draft, with extensive corrections, paper slightly browned, small portion of paper missing at lower edge, affecting some text on last two lines of pages 1-3, else in good, clean and legible condition.

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Thomas Moore (1760-1822) was a Quaker farmer, cabinetmaker and skilled engineer – who, in 1802, invented an ice box to transport butter from Georgetown (District of Columbia) to his home in Montgomery County, Maryland. His device was a tin box placed inside an oval cedar tub, the gaps between box and tub filled with ice, the whole then covered with a hinged lid and insulated on the outside with rabbit fur and coarse woolen cloth. He displayed the box to President Jefferson, a lover of novel inventions, who not only granted Moore a patent for his “Refrigerator” but bought one himself that was long used at Monticello. Moore recorded his accomplishment, and the new name he had given his invention, in a pamphlet published the following year, entitled: An Essay on the Most Eligible Construction of Ice-houses: Also, a description of the Newly Invented Machine Called the Refrigerator. (A rarity; the last copy at auction sold in the Streeter Sale, 1969, for $ 175).


Moore later established cotton mills in Maryland, oversaw construction projects on rivers and canals near Washington, D.C., and was appointed by Jefferson one of three commissioners to begin work on the first major highway in the United States to be built by the federal government, stretching from the Potomac to the Ohio River. At the time of his death, he was chief Engineer for the Virginia Board of Public Works.


Moore’s national reputation was such that Evans, President of the Schuylkill Navigation Company, consulted him about the best means of improving navigation along the most important Pennsylvania river canal. Moore responded with this long, somewhat rambling letter, which reads in part:


“Respected Friend,


     …I think the plan you purpose to accept for the improvement of the navigation of the Schuykill is on the whole a judicious one. The erection of dams across the River to be passed by a Lock at one end is a plain business in which I presume you will find no difficulty, but the selection of proper Sites and… the proper direction and length to using dams and… Jetties… will require the exercise of sound Judgment…I believe it will be found in practice that the plan of placing them alternately on the two sides of the River must be abandoned. When a dam is extended quite across a River the powers of art fairly overcome the resistance of the Stream by the strength of materials and the address by which they are combined, but in those practical kinds of operations, we must go hand in hand with nature or be content to have our views continually thwarted… if for the sake of producing regularity in our works we should project a Jettie from the lower end of a concave shore (where the laws that govern fluids in motion always produce a concentration of  current) in order to effect a passage for boats on the convex side, nature would laugh at our puny efforts by filling our canal…with sand… When the dams or Jetties are revised on Grand bottoms, the artificially excited current is always liable to scoop out the bed of the Sluice and deposit the contents somewhere at a short distance below which may cause an impediment where none existed before…The shape of the River and the materials of which the bottom is composed will of course be…considerations in determining the sites and shape of the works….I am not in possession of sufficient data to determine accurately the relative differences between propelling a boat by Setting Poles and…a toeing line but know it is very great… in favor of toeing. I have long been of opinion though I have never seen it tried that in many cases… instead of a toeing path, let a Chain be made fast in the bottom, a boats length above the rapid, and also at the lower end but of greater length than this distance between those points so as to lie slack on the bottom to be hooked up by boat hooks. I know of no way in which muscular power can be better applied…This plan would generally be less expensive than a toeing path.  I have no doubt from what I have seen… that six men with such a contrivance in a good boat would draw up as many Tons through a Sluice of one foot full in a hundred without the least difficulty and probably with but five minutes delay.  It would be very difficult and indeed impossible to describe on paper the best mode of overcoming every obstacle that will occur in the prosecution of such a work but a perfect knowledge of the principles… which govern the direction and deposition of ponderous bodies torn from their beds and put in motion by a current , proved by observation on what actually takes place in every stream, will go far towards giving… the best direction that the case admit of,  but in many instances must be judged of on the spot. A plan recommended by me some years ago for the construction of…dams has …lately been introduced on the Connecticut River which is…perhaps of all others the cheapest and probably none can… answer the purpose better.... information contained in this Letter will probably fall short of thy expectations but is all that occurs at present relative to a general outline which is all that can be given at a distance. If the hints communicated are of any value, they are at the service of the Schuykill Navigation Company.” [sic]