Nebulous Matter, 317 



upon the spot ; he is a good observer, and I will contradict no 

 one.'* 



It would be impossible to criticise Derham's st;ange con- 

 ception in a better spirit. I am only astonished that Voltaire, 

 who knew every thing, did not remember that the author 

 of the Astro-Theology was not the inventor of the empy^ 

 rean, Anaxagoras alleged that the upper regions (the ether) 

 were filled with fire. Seneca had said : Openings are some- 

 times formed in the heavens, through which we perceive the 

 flame which occupies the interior. In describing the nebulae 

 of Orion, Huygens expresses himself thus : *' One might say 

 that the celestial vault, having opened in this place, permits 

 us to behold the more luminous regions beyond." 



Finally, if such authorities, from their antiquity, do not ap- 

 pear to establish with sufficient evidence the fact that there is 

 something characteristic in the light which emanates from 

 true nebula*, I shall cite the recent words of Herschel the 

 younger ; '' In all the (resolvable) nebulae, the observer re- 

 marks (whatever may be the magnifying power) shootings 

 forth as from stars, or at least he believes that he feels as if 

 he would perceive them if his vision became more distinct. 

 The nebula of Orion produces an entirely different sensation, 

 giving rise to no idea of stars." 



Distribution of the phosphorescent matter in true Nebulae — 

 Modification which attraction produces in it with the lapse of 

 time. — The light of these great milky spots is generally very 

 feeble and uniform ; here and there only, we remark some 

 spaces a little more brilliant than the rest. 



On what can this augmentation of intensity depend ? Does 

 it depend on a greater concentration, or a greater depth in the 

 nebulous matter ? The choice between these two explanations 

 is not a matter of indifference. 



The places where a comparatively bright light is observed 

 in these great nebulosities, arc commonly of small extent. If, 

 then, we wish to ascribe the phenomenon to the greater depth 

 of the nebulous matter, it is necessary to suppose that a kind 

 of column of the same matter corresponds to each of the points 

 in question ; a rectilinear column, very condensed, and di^ 

 reeled exactly towards the earth. This specialty of direction 



