316 APPENDICES. 



(3) Political geography, the object of which is to consider the 

 earth as the habitat of the human species. It defines the territories 

 of different nations, and treats of population, morals, religion, 

 government, wealth, civilisation. It might be considered as a branch 

 of history and statistics. 



Geography has deserved the name of science only in modern 

 times, although the Arabs made great advance in it ; for in modern 

 times only have we arrived at a complete knowledge of our planet. 



Geology (y), earth, Xdyos, discourse), or the science of the earth, 

 treats of the physical constitution of our globe. It is called 

 geognosy when it is limited to the study of the structure, the 

 respective situation, and the nature of the matter composing the 

 earth ; but it receives the name of geogeny when it aims at com- 

 bining observed facts in order to ascend to the causes, finding the 

 laws which regulated the formation, and explaining the very origin 

 of our globe. 



This science is quite modern, although antiquity (Pythagoras, 

 Aristotle, and Strabo, for instance) had very clear notions about 

 geological problems; but until the Arabs and Leonardo da Vinci, 

 none of the germs of its study, which is one of persevering observa- 

 tion, can be said to have existed. 



As a practical science it is hardly necessary to point out how 

 important to our material welfare the study of the earth's crust is, 

 especially in these days when mining has become the greates 

 industry of mankind ; in its philosophical bearings it is of greater 

 importance still, throwing light as it does upon the history of extinct 

 species and the antiquity of man. 



Physics or Natural Philosophy (foais, nature). The most 

 extensive sense of natural philosophy is that which Sir John Herschel 

 has given to it, viz. : " to describe the phenomena of nature, to show 

 their cause?, and to analyse the constitution of the Universe." But 

 the study of nature has developed so immensely in recent times, 

 that natural philosophy has been divided into many branches, each 

 of which has received its characteristic denomination, such as heat, 

 optics, acoustics, magnetism, electricity, chemistry, etc. the last- 

 mentioned becoming an entirely distinct science. The chemist 

 studies the phenomena which depend upon the specific properties of 

 substances, whereas the physicist studies the phenomena which 

 result from the aggregate properties of bodies. At present, there- 

 fore, the name of natural philosophy is more or less restricted 

 to the knowledge of matter independently of the molecular composi- 

 tion of bodies. 



