NEBULAE. 31 



gion of the heavens. That which he names Nebulosa Ori 

 onis, and delineates in the vicinity of Nebulosa Prcesepe, ht 

 expressly declares to be an accumulation of small stars (stel 

 larum constipatarum) in the head of Orion. In the draw- 

 ing which he gives in the Siderius Nuncius, 20, extend- 

 ing from the girdle to the beginning of the right leg (a Ori- 

 oriis), I recognize the multiple star 6 above the star i. The 

 instruments employed by Galileo did not magnify more than 

 from eight to thirty times. It is probable that as the nebula 

 in the sword is not isolated, but appears, when seen through 

 imperfect instruments or a hazy atmosphere, like a halo round 

 the star 6, its individual existence and configuration may have 

 escaped the notice of the great Florentine observer. He was, 

 moreover, little inclined to assume the existence of nebulae.^ 

 It was not until fourteen years after Galileo's death, in the 

 year 1656, that Huygens first observed the great nebula of 

 Orion, of which he gave a rough sketch in the Sy sterna Satur- 

 nium, which appeared in 1659. "While," says this great 

 man, " I was observing, with a refractor of twenty-five feet 

 focal length, the variable belts of Jupiter, a dark central belt 

 in Ma.rs, and some faint phases of this planet, my attention 

 was attracted by an appearance among the fixed stars, which, 

 as far as 1 know, has not been observed by any one else, and 

 which, indeed, could not be recognized, except by such pow- 

 erful instruments as- 1 employ. Astronomers enumerate three 

 stars in the sword of Orion, lying very near one another. On 

 one occasion, when, in 1656, 1 was accidentally observing the 

 middle one of these stars through my telescope, I saw twelve 

 stars instead of a single one, which, indeed, not unfrequently 



(Opere di Galilei, Padova, 1744, torn, ii., . 14, No. 20) "which you 

 gave me includes the girdle and sword of Orion, and consequently also 

 the star 6; but it is difficult, owing to the striking inaccuracy of the 

 drawing, to recognize the three small stars in the sword (the middle 

 one of which is 6), and which appear to the unaided eye to be placed 

 in a straight line. I conjecture that you have correctly designated the 

 star i, and that the bright star to the right and below, or the one imme- 

 diately above it, is 0." Galileo expressly says, " In primo integram 

 Orionis Constellationem pingere decreveram : verum, ab ingenti stel- 

 larum copia, temporis vero inopia obrutus, aggressionem hanc in aliam 

 occasionem distuli." Considering Galileo's observation of the constel- 

 lation of Orion, we are the more struck by the circumstance that the 

 400 stars which he thought he had counted between the girdle and the 

 sword of Orion in a space often square degrees (Nelli, Vita di Galilei, 

 vol. i., p. 208), should subsequently (according to Lambert, Cosmolog. 

 Briefe, 1760, p. 155) have led him to the erroneous estimate of 1,650,000 

 stars for the whole firmament. (Struve, Astr. Stellaire, p. 14, and note 

 16.) * Cosmos, vol. ii., p. 331. 



