probably in 1872. He also may have met John Bartholomew Jr. (1831–1893) in Edinburgh, who created many maps in the same atlas. John Bartholomew became Petermann's student in Gotha in 1855 until 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. "Bartholomew is best known for the development of colour contouring (or hypsometric tints), the system of representing altitudes on a graduated colour scale, with areas of high altitude in shades of brown and areas of low altitude in shades of green. He first showcased his colour contouring system at the Paris Exhibition of 1878; although it initially met with skepticism, it went on to become standard cartographical practice". However, he might have picked up this idea during his time in Gotha as the colour scheme was first introduced by Emil von Sydow (1812–1873) in 1838 when he developed a color methodology for landscape features using hachures, where green was depicted for lowlands and brown used for highlands. The white for the higher reaches might later have been used by Hermann Haack (1872–1966) for his Perthes' wall maps. Several maps were co-constructions of Petermann and Bartholomew. London In 1847, Petermann moved to London with the intention of furthering his geographical studies and then returning to Germany. Soon, however, he decided to follow a professional career there as the environment he moved into seemed to be favorable for his prospects. In London, he worked as a reporter for a London periodical (Athenaeum, journal of literature, science and the fine arts. London, 1828–1921), and in 1850 founded his own establishment: The Geographical Establishment, Engraving, Lithographic and Printing Office, 9 Charing Cross. In 1852 the young Ernst Georg Ravenstein (1834–1913) was apprenticed to him, before he went in 1855 into the service of the Topographical Department of the British War Office. Petermann's firm published, among other things, the Atlas of physical geography with descriptive letter press (1850, with Thomas Milner), and the Physical statistical maps of the British Isles, showing the geographical distribution of the population