NEWS FROM HERSCHEZS PLANET. 145 



atmosphere. One of these strong lines corresponds in 

 position with one of the lines of hydrogen. Now it 

 may seem at a first view that since the light of Uranus 

 is reflected solar light, we might expect to find in the 

 spectrum of Uranus the solar lines of hydrogen. But 

 the line in question is too strong to be regarded as 

 merely representing the corresponding line in the solar 

 spectrum ; indeed, Dr. Huggins distinctly mentions 

 that ' the bands produced by planetary absorption are 

 broad and strong in comparison with the solar lines.' 

 We must conclude, therefore, that there exists in the 

 atmosphere of Uranus the gas hydrogen, sufficiently 

 familiar to us as an element which appears in combi- 

 nation with others, but which we by no means recognise 

 as a suitable constituent (at least to any great extent) 

 of an atmosphere which living creatures are to breathe. 1 

 And not only must hydrogen be present in the atmo- 

 sphere of Uranus, but in such enormous quantities as 

 to be one of the chief atmospheric constituents. The 

 strength of the hydrogen line cannot otherwise be 

 accounted for. If by the action of tremendous heat 

 all the oceans of our globe could be changed into their 

 constituent elements, hydrogen and oxygen, it is pro- 

 bable that the signs by which an inhabitant of Venus 

 or Mercury could recognise that such a change had 

 taken place would be very much less marked than the 

 signs by which Dr. Huggins has discovered that hydro- 



1 Traces of hydrogen can nearly always be detected in the air, but 

 the quantity of hydrogen thus shown to be present is almost infinitesi- 

 mally small compared with the amount of oxygen and nitrogen. 



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