346 IIUMBOLDT'S COSMOS : 



superficial extent, and intensity of light, but from their dis- 

 tance rendering it uncertain what are their true relations in 

 these respects. This distance is one strictly immeasurable. 

 The calculated distances of certain of the fixed stars of 

 which we have already spoken, enormous though these are, 

 scarcely furnish a unit for the comparison. Approximations, 

 indeed, have been made, but by methods which it would 

 require more space than we can give to render intelligible. 

 Without expatiating then on this point, of which neither 

 language nor figures can convey any true conception, we may 

 state generally that the observation of the nebulae is every 

 year affording facts and problems of higher interest. Here 

 are separate systems of worlds, numerous as above described, 

 and each comprising probably as many as our own vast system 

 of Suns. We have the common element of light, through 

 which alone, indeed, we know of their existence. Observa- 

 tion has disclosed to us the most singular varieties not 

 merely in the visible extent of these nebulaB, which simple 

 difference of distance might' produce but also in their con- 

 figuration and manner of condensation around centres ; imply- 

 ing forces of attraction which, in default of knowledge from 

 observation, we may reasonably from analogy suppose to be 

 the same as those governing our own planetary system. Other 

 direct means of knowledge regarding them we do not yet 

 possess. But time (if it be still sufficiently allotted to the 

 generations of man on the earth) and continuous observa- 

 tion by instruments of large and well-defined power, may 

 give us somewhat nearer access to the physical history of 

 these remote parts of the Universe. Every record of change 

 here whether it be concentration, diffusion, division, or 

 disappearance is a fact gained to science."* 



* February, 1862. Even at the moment of sending this sheet to the press, I 

 see a very interesting letter from Mr. Hind, relating, on the authority of several 

 eminent observers, the total disappearance of a small nebula, in the constella- 



