INTRODUCTION. 7 



la ted order, calls forth the feeling of tranquillity and repose. 

 This feeling takes from the unsearchable depths of space, as 

 of time, that which to the excited imagination had otherwise 

 attached to them, of shrinking awe. In all regions of the 

 earth, man, in the impulse of his natural sensibility, has 

 praised the " calm repose of a star-light summer night." 



If, then, immensity of space and magnitude of mass belong 

 especially to the Sidereal portion of the Physical Description of 

 the Universe, in which the eye is the only organ of contempla- 

 tion, on the other hand the Telluric portion has the more than 

 countervailing privilege, of offering a greater scientifically- 

 distinguishable variety in the multifarious elementary sub- 

 stances with which it is conversant. We are in contact with 

 terrestri;il nature through the medium of all our senses ; and 

 as astronomy, or the knowledge of moving luminous heavenly 

 bodies, has given occasion to the admirable augmentation 

 which has taken place in the brilliant domain of the higher 

 analysis and the wide range of optical science ; so, on the other 

 hand, it is the terrestrial sphere alone which, by the diversity 

 of substances, and the complicated action of the forces 

 manifested in those substances, has afforded the foundation 

 of chemistry, and of all those physical sciences which treat 

 of phenomena distinguishable from light- and heat-exciting 

 undulations. Each of these great divisions of the study of 

 Nature exercises, in virtue of the character of the problems 

 which it proposes for solution, a special influence on the 

 character of the intellectual labour to which it has given 

 rise, and to the enrichment of human knowledge which is 

 the fruit of that labour 



All cosmical bodies, excepting our own planet, and the 

 aerolites which are attracted by it, are, so far as we can 



