III. 



NUMBER, DISTRIBUTION, AND COLOR OF THE FIXED STARS. STEL- 

 LAR MASSES (STELLAR SWARMS). THE MILKY WAY INTERSPERSED 

 WITH A FEW NEBULOUS SPOTS. 



We have already, in the first section of this fragmentary 

 Astrognosy, drawn attention to a question first mooted by 

 Olbers.* If the entire vault of heaven were covered with 

 innumerable strata of stars, one behind the other, as with a 

 wide-spread starry canopy, and light were undiminished in 

 its passage through space, the sun would be distinguishable 

 only by its spots, the moon would appear as a dark disk, 

 and amid the general blaze not a single constellation would 

 be visible. During my sojourn in the Peruvian plains, be- 

 tween the shores of the Pacific and the chain of the Andes, 

 I was vividly reminded of a state of the heavens which, 

 though diametrically opposite in its cause to the one above 

 referred to, constitutes an equally formidable obstacle to hu- 

 man knowledge. A thick mist obscures the firmament in 

 this region for a period of many months, during the season 

 called el tiempo de la garua. Not a planet, not the most 

 brilliant stars of the southern hemisphere, neither Canopus, 

 the Southern Cross, nor the feet of the Centaur, are visible. 

 It is frequently almost impossible to distinguish the position 

 of the moon. If by chance the outline of the sun's disk be 

 visible during the day, it appears devoid of rays, as if seen 

 through colored glasses, being generally of a yellowish red, 

 sometimes of a white, and occasionally even of a bluish green 

 color. The mariner, driven onward by the cold south cur- 

 rents of the sea, is unable to recognize the shores, and in the 

 absence of all observations of latitude, sails past the harbors 

 which he desired to enter. A dipping needle alone could, 

 as I have elsewhere shown, save him from this error, by the 

 local direction of the magnetic curves. f 



Bouguer and his coadjutor, Don Jorge Juan, complained, 

 long before me, of the " unastronomical sky of Peru." A 

 graver consideration associates itself with this stratum of 

 vapors, in which there is neither thunder nor lightning, in 

 consequence of its incapacity for the transmission of light or 

 electric charges, and above which the Cordilleras, free and 

 cloudless, raise their elevated plateaux and snow-covered 



* Vide supra, p. 38, and note. 



t Cotmos, vol. i., p. 178, and note. 



