148 TERRESTRIAL PHENOMENA. 



of their exterior than of their interior." They have been 

 weighed and measured; thanks to the progress of astrono- 

 mical observation and calculation, their volumes and their 

 densities are known with constantly increasing numerical 

 exactness; but (with perhaps an exception in some degree 

 in the case of the Moon), a profound obscurity still veils 

 from us their physical properties. It is only on our own 

 globe that immediate proximity places us in relation with all 

 the elements both of the organic and the inorganic crea- 

 tion. The rich diversity of materials, their admixtures and 

 transformations, and the ever changing play of the forces 

 elicited, offer to the spirit of investigation appropriate and 

 welcome food ; and the immeasurable field of observation in 

 which the intellectual activity of the human mind can here 

 expatiate, lends to it a portion of its own elevation and 

 grandeur. The world of sensible phenomena reflects itself 

 into the depths of the world of ideas, and the rich variety of 

 nature gradually becomes subject to our intellectual domain. 

 I here touch again upon an advantage to which I. 

 have already repeatedly alluded, possessed by that portion of 

 our knowledge which is especially connected with our 

 terrestrial habitation. Uranography, or the description of 

 the heavens, from the remotely gleaming nebulous stars to 

 the central body of our own system, is limited to general 

 conceptions of volume and mass ; no vital activity is there 

 revealed to our senses ; it is only by means of resemblances, 

 and often fanciful combinations, that even conjectures have 

 been hazarded respecting the specific nature of the material 

 elements, and their presence or absence in this or that 

 cosmical body. The heterogeneity of matter, its chemical 

 diversity, the regular forms into winch its particles arrange 



