AND OF THE OTHER BODIES OF SPACE. 21 



under which the laws operate, and consequently the ef- 

 fects which they produce. Thus, there may be substan- 

 ces here which are not in some other bodies, and substances 

 here solid may be elsewhere liquid or vaporiform. We are 

 the more entitled to draw such conclusions,seeingthat there 

 is nothing at all singular or special in the astronomical si- 

 tuation of the earth. It takes its place third in the series of 

 planets, which series is only one of numberless other sys- 

 tmes forming one group. It is strikingly, if I may use such 

 an expression, a member of a democracy. Hence, we cannot 

 suppose that there is any peculiarity about it which does not 

 probably attach to multitudes of other bodies, in fact, to all 

 that are analogous to it in respect of cosmical arrangements. 



It therefore becomes a point of great interest — what are 

 the materials of this specimen ? What is the constitu- 

 tional character of this object, which may be said to be 

 a sample, presented to our immediate observation, of those 

 crowds of worlds which seem to us as the particles of the 

 desert sand-cloud in number, and to whose profusion there 

 are no conceivable local limits ? 



The solids, liquids, and aeriform fluids of our globe are 

 all, as has been stated, reducible into fifty- rive substances 

 hitherto called elementary. Six are gases ; oxygen, hy- 

 drogen, and nitrogen being the chief. Forty-two are 

 metals, of which eleven are remarkable as composing, in 

 combination with oxygen, certain earths, as magnesia 

 lime, alumin. The remaining six, including carbon, si- 

 licon, sulphur, have not any general appellation. 



The gas oxygen is considered as by far the most abun- 

 dant substance in our globe. It constitutes a fifth part of 

 our atmosphere, a third part of water, and a large propor- 

 tion of every kind of rock in the crust of the earth. Hy- 

 drogen, which forms two-thirds of water, and enters into 

 some mineral substances, is perhaps next. Nitrogen, ot 

 ^rhich the atmosphere is four-fifths composed, must be 

 considered as an abundant substance. The metal silicium 

 which unites with oxygen in nearly equal parts to form 

 silica, the basis of nearly half of the rocks in the earth's 

 crust, is, of course, an important ingredient. Aluminium 

 the metallic basis of alumin, a large material in many 

 rocks, is another abundant elementary substance. So, 

 also, is carbon, a small ingredient in the atmosphere, but 

 the chief constituent of animal and vegetable substances, 

 and of all fossils which ever were in the latter condition, 



