1 82 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



have all the researches and observations of others, been 

 combined with greater completeness or with clearer philo- 

 sophical conceptions than by Ritter in his monumental work 

 on Asia. He has endeavoured to replace the meagre 

 descriptions of his predecessors by a chorological representa- 

 tion ; he has gathered information from the most varied 

 sources and kneaded it into an organic and intellectual whole, 

 united by the principle of causality." (The Tasks and Methods 

 of Modern Geography ', Leipzig, 1883.) 



During the latter half of this century the abundance of new 

 facts brought home by travellers of all nations has extended 

 our knowledge with remarkable rapidity. But the treatment 

 of the subject remained for a long time of the more formal 

 and descriptive character. Most travellers contented them- 

 selves with descriptions more or less accurate and with 

 measurements, and were indifferent to the genetic aspects of 

 geography. 



If we except the older works, that of Humboldt may be 

 said to have laid the scientific foundation of a morphological 

 treatment of surface forms. His calculations of the average 

 height of the great continents form the starting-point of a 

 series of investigations, amongst which may be mentioned 

 those of A. de Lapparent (1883), Von Tillo (1889), John 

 Murray (1886), and of a number of eminent younger 

 geographers. By the side of orography, oceanography has 

 made even more remarkable progress during the century, and 

 has developed itself into an independent branch of the 

 morphology of the earth's surface. Otto gave in 1808 a fairly 

 complete account of the limited facts then known about ocean 

 forms. Great advances had been made when the American 

 sailor Maury published his excellent work fifty years later. 

 Maury gave a general idea of the extent of the ocean surfaces, 

 the forms of coast-lines, the ocean tides and currents, the 

 physical and chemical conditions of the water and the various 

 organisms that inhabit the oceans, and was also enabled, with 

 the help of three lines measured for the laying of the 

 Transatlantic cables, to sketch the first section and the first 

 map of the floor of the North Atlantic ocean. From these 

 data Peschel in 1868 calculated the mean depth of the North 

 Atlantic Ocean. 



A new era began in oceanography with the exploring 

 expeditions of the English Challenger, the German Gazelle, 



