392 



Dr. C. W. Siemens. 



[Mar. 2, 



perhaps the vaponr escaped observation, or was expelled to a greater 

 extent than the other gases by external heat when the meteorolite 

 passed through our atmosphere. Opinions concur that the gases 

 found occluded in meteorolites cannot be supposed to have entered 

 into their composition during the very short period of traversing oar 

 atmosphere, but if any doubt should exist on this head, it ought to be 

 set at rest by the fact that the gas principally occluded is hydrogen, 

 which is not contained in our atmosphere in any appreciable quantity. 



Further proof of the fact that stellar space is filled with gaseous 

 matter is furnished by spectrum analysis, and it appears from recent 

 investigation, by Dr. Huggins and others, that the nucleus of a comet 

 contains very much, the same gases found occluded in meteorolites, 

 including " carbon, hydrogen, nitrogen, and probably oxygen," whilst, 

 according to the views set forth by Dewar and Liveing, it also con- 

 tains nitrogenous compounds such as cyanogen. 



Adversely to the assumption that interplanetary space is filled 

 with gases, it is urged that the presence of ordinary matter would 

 cause sensible retardation of planetary motion, such as must have 

 made itself felt before this ; but assuming that the matter filling space 

 is an almost perfect fluid not limited by border surfaces, it can be 

 shown on purely mechanical grounds, that the retardation by friction 

 through such an attenuated medium would be very slight indeed, even 

 at planetary velocities. 



But it may be contended that, if the views here advocated regard- 

 ing the distribution of gases were true, the sun should draw to himself 

 the bulk of the least diffusible, and therefore the heaviest gases, such 

 as carbonic anhydride, carbonic oxide, oxygen and nitrogen, whereas 

 spectrum analysis has proved on the contrary a prevalence of 

 hydrogen. 



In explanation of this seeming anomaly, it can be shown in the first 

 place, that the temperature of the sun is so high, that such compound 

 gases as carbonic anhydride and carbonic oxide, could not exist within 

 him; it has been contended, indeed, by Mr. Lockyer, that none of 

 the metalloids have any existence at these temperatures, although as 

 regards oxygen, Dr. Draper asserts its existence in the solar photo- 

 sphere. There must be regions, however, outside that thermal limit, 

 where their existence would not be jeopardised by heat, and here great 

 accumulation of those comparatively heavy gases that constitute our 

 atmosphere would probably take place, were it not for a certain 

 counterbalancing action. 



I here approach a point of principal importance in my argument, 

 upon the proof of which my further conclusions must depend. 



The sun completes one revolution on its axis in 25 days, and its 

 diameter being taken at 882,000 miles, it follows that the tangential 

 velocity amounts to T25 miles per second, or to 441 times the 



