THOUGHTS ON NATURAL PHILOSOPHY. 2/ 



scope of large light-grasping power it becomes one 

 of the most impressive of natural objects, though the 

 vast extension of the heavens into which its wreaths 

 are thrown, and the abundance of delicate detail 

 permeating the whole, have only become revealed in 

 recent records of the photographic plate. 



The Nebula of Orion appears through a fine tele- 

 scope as a faint green haze, suggesting a light cloud 

 floating in celestial space, in form not very unlike 

 that of the profile of a fish's mouth. The whole is 

 composed of clouds of light of different degrees of 

 brightness, some of extreme fantastic, and not a few 

 of highly suggestive forms. It is in the perception 

 of these that the photographic plate has demon- 

 strated, as powerfully as in any of its applications, 

 its great superiority over the eye in its capacity of 

 appreciating the faintest shades of light. Structure 

 is revealed throughout the whole nebula by the 

 manner in which streams of luminous matter are 

 directed from a brilliant and nearly central region 

 in close proximity to the mouth-like bay of dark 

 sky, the importance of this region being emphasized 

 by the occurrence in it of a remarkable group of 

 stars " the trapezium of Orion " and in the sym- 

 metrical arrangement of many of the cloud-forms 

 with reference to it. Many stars are scattered over 

 the picture; that those of the trapezium are actually 

 involved in the glowing wreaths of the nebula itself, 

 and do not owe their appearance in it to the effect 

 of optical projection, either by their lying by chance 

 in the line of sight towards the nebula, or by 

 being visible through its transparent substance w r hile 



