INTRODUCTION. 



SPECIAL RESULTS OF OBSERVATION IN TIIE DOMAIN 

 OF TELLURIC PHENOMENA. 



In a work embracing so wide a field as the Cosmos, which 

 aims at combining perspicuous comprehensibility with gen- 

 eral clearness, the composition and co-ordination of the whole 

 are, perhaps, of greater importance than copiousness of detail. 

 This mode of treating the subject becomes the more desira- 

 ble because, in the Book of Nature, the generalization of 

 views, both in reference to the objectivity of external phe- 

 nomena and the reflection of the aspects of nature upon the 

 imagination and feelings of man, must be carefully separated 

 from the enumeration of individual results. The first two 

 volumes of the Cosmos were devoted to this kind of general- 

 ization, in which the contemplation of the Universe was con- 

 sidered as one great natural whole, while at the same time 

 care was taken to show how, in the most widely remote zones, 

 mankind had, in the course of ages, gradually striven to dis- 

 cover the mutual actions of natural forces. Although a great 

 accumulation of phenomena may tend to demonstrate their 

 causal connection, a General Picture of Nature can only pro- 

 duce fresh and vivid impressions when, bounded by narrow 

 limits, its perspicuity is not sacrificed to an excessive aggre- 

 gation of crowded facts. 



As in a collection of graphical illustrations of the surface 

 and of the inner structure of the earth's crust, general maps 

 precede those of a special character, it has seemed to me that 

 in a physical description of the Universe it would be most 

 appropriate, and most in accordance with the plan of the 

 present work, if, to the consideration of the entire Universe 

 from general and higher points of view, I were to append in 

 the latter volumes those special results of observation upon 

 which the present condition of our knowledge is more partic- 

 ularly based. These volumes of my work must, therefore, 

 in accordance with a remark already made (Cosmos, vol. iii., 

 p. 5-9), be considered merely as an expansion and more 

 careful exposition of the General Picture of Nature (Cosmos, 



