I have undertaken a Map of Virginia and anxious to give it all the Correctness, which the best observations can afford, find myself almost obliged to request your Aid. There is a Map by Col. Francis Deakens,1 in the Possession of Mr Geo. Fenwick, of Washington,2 with a Number of Notes describing the Potowmac River, & the Line between Maryland & Virginia, with the Roads, Water Courses Etc, which, it is thought, would be interesting, & might be either copied, or obtained from Mr Fenwick. Should it be perfectly convenient to you to make Inquiry concerning the Map, & the Notes, &, if they can be obtained, to forward them to me, you would oblige me greatly; provided you think any useful & accurate Information can be collected from them. I have the Map of Maryland by Griffith;3 perhaps it may be founded upon the observations of Deakins; if so, that Circumstance wd supercede the Necessity of recurring to Mr Fenwick. What is the Opinion of Griffith’s Map, as to the Potowmack, & Maryland Line? This Question, perhaps, you can solve, or collect from Inquiry. What is the Long. of Washington, as given by Ellicott, either from Phila. or London, or Paris? He, no Doubt, determined that Point; & yet I do not find it any where stated.

If our valuable Friend Mr Jefferson has collected any Observations as to the Long. & Lat. of important Positions in Virga, or of any Places in it, since the Publication of his Map, I wd thank him for them. Ferrer’s4 I have bt, if any Observations of the Kind have been presented to you, which may be useful, I will thank you for them. Perhaps some Surveys of our Coast may have been made under the Authority of Govt. Yrs sincerely & Affy.