NEBULAE. . 19 



ula in the sword of Orion, which is so important from its 

 extent and form, and has become so famous from the num- 

 ber and celebrity of its subsequent investigators.* Huygens 

 was the means of inducing Picard (in 1676) to devote himself 

 diligently to the investigation of this nebulous body. Ed- 

 mund Halley, during his sojourn in St. Helena in 1677, was 

 the first to determine .any of the nebulous spots belonging to 

 portions of the southern heavens not visible in Europe, al- 

 though his observations embraced only a very small number. 

 The lively interest taken by the great Cassini (Jean Dom- 

 inique) in all branches of contemplative astronomy, led him, 

 toward the close of the seventeenth century, to a more care- 

 ful exploration of the nebula? in Andromeda and Orion. He 

 thought he could detect alterations in the latter since Huy- 

 gens's observations, and that he " had recognized stars in the 

 former which could not be seen with telescopes of low pow- 

 ers." There are reasons for regarding the assertion of an 

 alteration of figure as a delusion ; not entirely so the exist- 

 ence of stars in the nebula in Andromeda since the remark- 

 able observations of George Bond. Cassini, moreover, con- 

 jectured, on theoretical grounds, the possibility of such a res- 

 olution of the nebula ; since, in direct opposition to Halley 

 and Derham, he considered all nebulous spots to be very re- 

 mote stellar swarms. f The faint mild effulgence in Androm- 

 eda was indeed, according to his opinion, analogous to the 

 zodiacal light, which he also conjectured to be composed of a 

 crowd of densely, thronged, small planetary bodies. $ Lacaille's 

 residence in the southern hemisphere (at the Cape of Good 

 Hope, and in the Isle of France and Bourbon, between 1750- 

 1752), so considerably increased the number of known nebu- 

 lous spots, that Struve has justly remarked, that from the ob- 

 servations of this traveler more was known, at that time, of 



* Huygens, Systema Saturnium, in his Opera varia, Lugd. Bat, 1724, 

 "torn, ii., p. 523 and 593. 



t "Dans les deux ntbuleuses d'Andromede et d'Orion, j'ai vu des 

 etoiles qu'on n'apenjoit pas avec des lunettes communes. Nous ne sa- 

 vons pas si Ton ne pourrait pas avoir des lunettes assez grandes pour 

 que toute la nebulosite put se resoudreen de plus petites etoiles, comme 

 il arrive a celle du Cancer et du Sagittaire." " I have seen stars in the 

 nebula of Andromeda and Orion," says Dominique Cassini, " which can 

 not be recognized by ordinary instruments. We are ignorant whether 

 telescopes may not be constructed of sufficient power to resolve the 

 whole nebula into smaller stars, as has been done in the case of the 

 nebulae in Cancer and Sagittarius." Delambre, Hist, de VAstr. Mo- 

 derne, torn, ii., p. 700 and 744. 



t Cosmos, vol. i., p. 141, note. 



