New and Accurate Maps of the Counties of England and Wales
Gibson based his small map of Essex on Warburton.
The atlas was published by John Newbery, who was an early specialist in books for children. This presumably explains why the map is so small and has so little detail.
A further version was reissued sometime after 1779, with unchanged maps, with just a change of seller (to T Carnan).
Displayed scale of 10 miles = 26.2mm, or 9.7 miles/inch; actual scale = 19.0 miles/inch, or 1:1,200,000. The map's scale is thus wrong by a factor of two - perhaps someone read their information incorrectly?