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COXSTITUEXT MATEELVLS OF THE EAETH 



AND OF THE OTIIEK BODIES OF SPACE. 



The nebular hypothesis ahnost necessarily supposes 

 matter to have originally formed one mass. We have 

 seen that the same physical laws preside over the whole. 

 Are we also to presume that the constitution of the 

 whole was uniform 1 — that is to say, that the whole con- 

 sisted of similar elements. It seems difficult to avoid 

 coming to this conclusion, at least under the qualification 

 that, possibly, various bodies, under peculiar circum- 

 stances attending their formation, may contain elements 

 which are wanting, and lack some which are present, in 

 others, or that some may entirely consist of elements in 

 which others are entirely deficient. 



What are elements? This is a term applied by the 

 chemist to a certain limited number of substances (fifty- 

 four or fifty-five are ascertained), which, in their com- 

 binations, form all the matters of every kind present 

 in and about our globe. They are called elements, or 

 simple substances, because it has hitherto been found 

 impossible to reduce them into others, wherefore they 

 are presumed to be the primary bases of all matters. It 

 has, indeed, been surmised that these so-called elements 

 are only modifications of a primordial form of matter, 

 brought about unrlor certain conditions; but if this 



