520 Mr. W. Huggins and Dr. W. A. Miller on the 



sphere of "fog" will not explain the absorption of the less re- 

 frangible portion of the luminous spectrum. 



21. These spectrum observations are not without interest also 

 when viewed in connexion with the nebula?* hypothesis of the cos- 

 mical origin of the solar system and fixed stars. For if it be 

 supposed that all the countless suns which are distributed through 

 space, or at least those of them which are bright to us, were once 

 existing in the condition of nebulous matter, it is obvious that, 

 though certain constituents may have been diffused throughout 

 its mass, yet the composition of the nebulous material must have 

 differed at different points ; otherwise, during the act of agglo- 

 meration, each system must have collected and condensed equal 

 proportions of similar materials from the mass around. It can- 

 not be supposed that similarity in physical properties has caused 

 the association of the different elements : we find, for example, 

 some of the least volatile of the metals, such as iron, associated 

 with highly volatile elements, such as mercury and tellurium, in 

 the same star. 



If we may so say, there seems to be some analogy between this 

 irregular distribution of the elements in different centres in space, 

 and the manner in which the components of the earth's crust are 

 distributed. Upon the earth there are certain very generally 

 diffused elements, such as oxygen, hydrogen, carbon, silicon, 

 iron, aluminium, and calcium, which occur in all parts ; whilst 

 there are others which, like silver, tin, lead, and other metals, 

 are accumulated at particular points only. Whatever may have 

 been the physical causes which may have produced this separa- 

 tion, we see abundant evidence of the advantage of this distribu- 

 tion in their application to the purposes of man — smallness in 

 relative amount being compensated for by the accumulation of 

 the material in denser deposits, which allow of their compara- 

 tively easy extraction to supply the wants of mankind. If this 

 arrangement be admitted as designed in the case of the earth, is 

 it going beyond the limits of fair deduction to suppose that, were 

 we acquainted with the economy of those distant globes, an 

 equally obvious purpose might be assigned for the differences in 

 composition which they exhibit ? 



22. The additional knowledge which these spectrum observa- 

 tions give us of the nature and of the structure of the fixed stars, 

 seems to furnish a basis for some legitimate speculation in refer- 

 ence to the great plan of the visible universe, and to the special 

 object and design of those numerous and immensely distant orbs 

 of light. 



The closely marked connexion, in similarity of plan and mode 

 of operation, in those parts of the universe which lie within the 

 range of experiment, and so of our more immediate knowledge, 



