26 THOUGHTS ON NATURAL PHILOSOPHY. 



same stage of development, it would follow that, 

 since they differ enormously in mass, they would 

 cool and therefore pass through their life stages at 

 different rates. It becomes, therefore, of great 

 interest to inquire whether there exist in celestial 

 space extensive bodies of gas, and whether there 

 exist dark stars. The answer is clear: astronomical 

 observation has revealed both. 



There can be little doubt that the earliest stage of 

 star-life is represented in at any rate many of the 

 nebulae. The nebulae appear as faint clouds of light, 

 and are distributed in thousands over the face of the 

 heavens. The greater number are excessively faint, 

 their very detection demanding the aid of the highest 

 optical power; while two only, and those just hover- 

 ing upon the verge of vision, are visible to the eye 

 upon the darkest and clearest nights. These are the 

 glorious objects in the constellations of Andromeda 

 and Orion, the one in Orion being the more im- 

 pressive of the two. 



The Great Nebula of Orion is situated near the 

 centre of a line of faint stars that trail southward 

 from the middle of a line formed by the three bright 

 ones that constitute the " belt " of the familiar winter 

 constellation Orion. Visible to the naked eye under 

 favourable conditions as a faint mist 



A single misty star, 

 Which is the second in a line of stars, 

 That form a sword beneath a belt of three; 



its cloudy nature clearly revealed in a hand telescope 

 or a good field-glass; when viewed through a tele- 



