section_path: Definition/History of the concept/Modern definitions
section_name: Modern definitions
paragraph_text: Modern definitions
  
  The question of defining a precise eastern boundary of Europe arises in the Early Modern period, as the eastern extension of Muscovy began to include North Asia. Throughout the Middle Ages and into the 18th century, the traditional division of the landmass of Eurasia into two continents, Europe and Asia, followed Ptolemy, with the boundary following the Turkish Straits, the Black Sea, the Kerch Strait, the Sea of Azov and the Don (ancient Tanais). But maps produced during the 16th to 18th centuries tended to differ in how to continue the boundary beyond the Don bend at Kalach-na-Donu (where it is closest to the Volga, now joined with it by the Volga–Don Canal), into territory not described in any detail by the ancient geographers.
  
  Around 1715, Herman Moll produced a map showing the northern part of the Ob River and the Irtysh River, a major tributary of the Ob, as components of a series of partly-joined waterways taking the boundary between Europe and Asia from the Turkish Straits, and the Don River all the way to the Arctic Ocean. In 1721, he produced a more up to date map that was easier to read. However, his proposal to adhere to major rivers as the line of demarcation was never taken up by other geographers who were beginning to move away from the idea of water boundaries as the only legitimate divides between Europe and Asia.
  
  Four years later, in 1725, Philip Johan von Strahlenberg was the first to depart from the classical Don boundary. He drew a new line along the Volga, following the Volga north until the Samara Bend, along Obshchy Syrt (the drainage divide between the Volga and Ural Rivers), then north and east along the latter waterway to its source in the Ural Mountains. At this point he proposed that mountain ranges could be included as boundaries between continents as alternatives to nearby waterways. Accordingly, he drew the new boundary north along Ural Mountains rather than the nearby and parallel running Ob and Irtysh rivers. This was endorsed by the Russian Empire and introduced the convention that would eventually become commonly accepted. However, this did not come without criticism. Voltaire, writing in 1760 about Peter the Great 's efforts to make Russia more European, ignored the whole boundary question with his claim that neither Russia, Scandinavia, northern Germany, nor Poland were fully part of Europe. Since then, many modern analytical geographers like Halford Mackinder have declared that they see little validity in the Ural Mountains as a boundary between continents.
  
  The mapmakers continued to differ on the boundary between the lower Don and Samara well into the 19th century. The 1745 atlas published by the Russian Academy of Sciences has the boundary follow the Don beyond Kalach as far as Serafimovich before cutting north towards Arkhangelsk, while other 18th- to 19th-century mapmakers such as John Cary followed Strahlenberg's prescription. To the south, the Kuma–Manych Depression was identified c. 1773 by a German naturalist, Peter Simon Pallas, as a valley that once connected the Black Sea and the Caspian Sea, and subsequently was proposed as a natural boundary between continents.
  
  By the mid-19th century, there were three main conventions, one following the Don, the Volga–Don Canal and the Volga, the other following the Kuma–Manych Depression to the Caspian and then the Ural River, and the third abandoning the Don altogether, following the Greater Caucasus watershed to the Caspian. The question was still treated as a "controversy" in geographical literature of the 1860s, with Douglas Freshfield advocating the Caucasus crest boundary as the "best possible", citing support from various "modern geographers".
  
  In Russia and the Soviet Union, the boundary along the Kuma–Manych Depression was the most commonly used as early as 1906. In 1958, the Soviet Geographical Society formally recommended that the boundary between the Europe and Asia be drawn in textbooks from Baydaratskaya Bay, on the Kara Sea, along the eastern foot of Ural Mountains, then following the Ural River until the Mugodzhar Hills, and then the Emba River; and Kuma–Manych Depression, thus placing the Caucasus entirely in Asia and the Urals entirely in Europe. The Flora Europaea adopted a boundary along the Terek and Kuban rivers, so southwards from the Kuma and the Manych, but still with the Caucasus entirely in Asia. However, most geographers in the Soviet Union favoured the boundary along the Caucasus crest, and this became the common convention in the later 20th century, although the Kuma–Manych boundary remained in use in some 20th-century maps.
  
  Some view the separation of Eurasia into Asia and Europe as a residue of Eurocentrism: "In physical, cultural and historical diversity, China and India are comparable to the entire European landmass, not to a single European country.."