The southern chart is based on the surveys of John Knight, who was working in the Cape Code and Rhode Island region at this time.  This part of the chart shows a concentration of soundings and details of sand banks and shoals, and was the type of chart which mariners would rely upon. 

The northern part of the chart, where Des Barres himself did a lot of early surveying work between Casco Bay and Halifax, depicts the coastline with far less nautical or hydrographic information.  On this section of the chart, Des Barres has taken care to include detailed depictions of rivers, tributaries and mountain relief north of Newburyport. 

Overall, this chart offers a small scale view of the whole of one of the most important areas of North America showing all of the major settlements, but it was clearly produced from a combination of existing work rather than from one coherent project. 

Herein lies the clue as to why it was put together in such an unusual way.  At a time when the conflict in the War of Independence was at its peak, there was a veritable thirst for information back in Britain, and Des Barres was doing all he could to quench that thirst for knowledge and news.  He would undoubtedly have made use of whatever information he had at his disposal, and this would have included existing surveys (complete or not) made by the teams of surveyors, map-makers and hydrographers working up and down the North American Atlantic coast at the time.  By combining and redrawing existing works, he was able to conjure such presentations.   When looking down the coastline depicted in this magnificent chart it is important to remember that each town, cove and bay has its own tale of importance related to the conflict that was the War for Independence.