During his time in Edinburgh he may have come into contact with the publisher G.H. Swanston, for whom he constructed several maps for The Royal Illustrated Atlas, Of Modern Geography, 1st edition published in 27 parts 1854–62. and republished probably in 1872. He also may have met in Edinburgh with John Bartholomew Jr. (1831–1893), who created many maps in the same atlas. John Bartholomew became Petermann's student in Gotha from 1855 till he was recalled to his father's firm in 1856. The German school of cartography was pre-eminent, and four generations of Bartholomews widened their knowledge by studying with the German masters. John George's son Ian studied in Leipzig (1907–08) with Oswald Winkel. His grandson John Christopher carried on the tradition, studying with Eduard Imhof, the great Swiss cartographer, in Berne and Zurich in 1960, and his son John Eric followed in 1977 with Imhof's pupil, Ernst Spiess.