A Chart of the Harbour of Boston with the Soundings, Sailing-Marks and Other Directions details the coastal waters and their sand bars and rocks. Land features are referenced from the point of view of sailors: hills, towns, and areas under cultivation. "Best channels" are defined by sightlines that align landmarks like "Charlestown Tree and Outer Angle of the North Battery".

Prepared for the Royal Navy at the outset of the American Revolution, the chart offers fascinating and explicit directions: "If bound to Boston cross St. George's Bank in Latitude 42d 25m N if you can -- Steer W. by N. by Compass 65 Leagues for the Light House of Boston. In the above Latitude in coming first on the Bank, you will have 90 Fathoms, and then Shoal it to 36 Fathoms from the Shoalest Part."

This definitive Revolutionary era chart of Boston's harbor is based on the surveys of Samuel Holland, the British Surveyor General of Quebec who was given the responsibility of surveying all British possessions north of the Potomac River. Holland, an engineer and hydrographer, directed a team of six surveyors, 35 assistants, and four local guides to survey more than 3,000 miles of New England coastline, estuaries, and islands.

About Thomas Jefferys

Jefferys was the leading British chart and mapmaker of the pre-Revolutionary era and the "Geographer to His Royal Highness the Prince of Wales". His American Atlas was published posthumously by Robert Sayer from 1774 to 1782. Sayer and his partner, John Bennett, took over Jefferys' business after his death in 1771.