138 IN STARRY REALMS. 



one ingredient which we know well on the eurth. Pre- 

 vious to actual trial no one would have expected, I think, 

 to find the Great Nebula largely constituted from such a 

 familiar element as hydrogen. This gas enters into the 

 composition of water, and is thus an element of extreme 

 abundance on the earth. That an element so common with 

 us here should also be abundant in these awfully distant 

 regions of the universe is one of the most astonishing 

 facts that modern science has revealed. 



As the eye follows these ramifications of the Great 

 Nebula, ever fading away in brightness until it dissolves 

 in the blackness of the sky ; as we look at the multitudes 

 of bright stars which sparkle out from the depths of the 

 great glowing gas ; as we ponder on the marvellous out- 

 lines of a portion of the nebula, we are tempted to 

 ask what the true magnitude of this object must really be. 

 Here, again, we have to confess that science is unable to 

 satisfy this very legitimate curiosity. The only means 

 of learning the true length and breadth of a celestial 

 object depends upon our first having discovered the dis- 

 tance from us at which the object is situated. Unhappily 

 we are, as I have said, entirely ignorant of what this 

 distance may be in the case of the Great Nebula in Orion. 

 Our ordinary methods of conducting such an inquiry are 

 hardly applicable to such an object, and its position so 

 near the equator introduces fresh difficulties into the 

 problem. We shall, however, certainly not err on the side 

 of exaggeration if we assert that the Great Nebula must 

 be many millions of times larger than that group of bodies 

 which we call the solar system. 



There are many other nebulae which would be well 



