34 THOUGHTS ON NATURAL PHILOSOPHY. 



tinuous " spectra, spectra in which all shades of 

 colour were represented, and might, therefore, so far 

 as spectroscopic evidence was concerned, consist of 

 systems of stars, of gas possessing comparatively 

 high density, or of gas in an incipient stage of 

 condensation. The structure of some of these as 

 revealed by the photographic plate lends strong 

 support to the last hypothesis; in the Great Nebula 

 in Andromeda, for instance, it is scarcely possible 

 not to recognize the process of condensation as 

 actually in progress. Nearly one-half of the nebulae 

 owe their luminosity to the presence in them of 

 glowing gas. 



It is difficult not to see in the gaseous nebulae the 

 stuff of which future stars will be made. Granting 

 that their substance is subject to the law of gravita- 

 tion, it appears certain that in coming ages their 

 glowing matter must, under its influence, be drawn 

 towards centres of condensation ; the smaller and 

 more symmetrical of the nebulae possibly developing 

 into single stars, but such majestic collections of 

 cloudy structures as are revealed in Orion being 

 more probably the origin of hosts of separate suns." 



The Nebulae, and other material phenomena, are 

 the result of matter in motion, or material motion. 



Material motion gives the sensation of heat, and 

 is called " energy." The word " energy " is only a 

 name given to material motion. 



Electricity and magnetism are material motion in 

 special forms or modes, and only in operation when 

 material motion takes those forms or modes. This 

 accounts for the fact that in nature there may be 



