A very nicely prepared atlas, the title of which as the arms of Scotland, and a view showing a factory with arms and ammunition in the foreground, and ships on the water in the distance. First published in 1771, by Sayer and Bennett, it was re-issued in 1787 by Robert Sayer and finally in 1794, three years after the death of its author. The maps are clearly engraved and each one is accompanied by a page of text. After the engraved title and index is an attractive general map and "A Concise Description of Scotland" on four pages followed by 27 finely engraved maps in full wash colour without an imprint. The county maps are bound face to face with a sheet containing a short account of each county between them. Mostyn was the son of Andrew Armstrong, an accomplished engraver and map-maker and they worked together on many large-scale surveys in Scotland and Northern England. The Scottish surveys included fine maps of Ayrshire, Berwickshire, Peebleshire and the Lothians, whilst their English surveys included Durham and Northumberland, the quality of the latter earning them a £50 gratuity from the Society of the Arts following their announcement in 1762 to reward the maker of any county survey of great detail and accuracy. The maps for the 'Scotch Atlas' are based mainly on James Dorrett's six sheet map of Scotland published in 1750, but with improvements, many of which came from the surveys outlined above. There were further surveys by the Armstrongs in Cambridgeshire and Norfolk that did not result in publication, and it was left to Mostyn's 'Scotch Atlas' to seal his reputation as an outstanding surveyor and map maker.