[East Coast] — Heather, William, and John William Norie

Sea chart (25 3/4 x 63 in.; 654 x 1,600 mm), two sheets joined, original blue paper-backing, drawn by John William Norie and engraved by John Stephenson.

Clean split to fold, some wear to old folds occasionally affecting image.

Fisher, The Makers of the Blueback Charts pp. 74-83

Among Heather's earliest separately-issued blue-back charts of the American coast extending from Georgia to New Hampshire. For most of the eighteenth century, charts were sold bound in atlases. This greatly restricted their size and utility on board ship. As marine survey techniques became more accurate and it became worthwhile plotting on charts and solving navigational problems, charts needed to be laid flat on a table, which made bound charts impractical. After 1800, most commercial charts were sold loose. Their size increased dramatically, and they were backed with blue paper for strength (hence the term "blue back" chart). It was blue backs which were used by the British merchant ships all over the world in the great mercantile expansion of the nineteenth century.

The desirability of 18th century blue back sea charts is enhanced by their great scarcity due to their ephemeral nature: they were easily damaged on board ship and were frequently destroyed when updated charts were issued. The present map was re-issued by Norie later in the 19th century following Heather's death, but the present 18th-century first issue is excessively rare. We find no institutional holdings in North America of this 1795 first issue and only two copies of what appears to be the second issue dated 1799 (New York Public Library and Harvard). No copies of this map appear in the Map Price Record.