NEBULAE. 15 



If we take into account the number of objects discovered, 

 the accuracy of their telescopic investigation, and the gener 

 alization of views, the history of nebulous spots, like that of 

 double stars, may be said to begin with William Herschel. 

 Until his time there were not more than 120 unresolved neb- 

 ulae in both hemispheres whose positions were determined, 

 including even the results of Messier's meritorious labors ; 

 and in 1786 the. great astronomer of Slough published the 

 first catalogue, containing 1000. I have already fully point 

 ed out, in an earlier portion of this work, that the bodies 

 named nebulous stars (vs<pekoeidel(;) by Hipparchus and 

 Geminus in the Catasterisms of the pseudo-Eratosthenes 

 and in the Almagest of Ptolemy, are stellar clusters which 

 appear to the naked eye with a nebulous luster.* This des- 

 ignation, Latinized nebulosce, passed in the middle of the 

 thirteenth century into the Alphonsine Tables, probably 

 through the preponderating influence of the Jewish astrono- 

 mer, Isaac Aben Sid Hassan, chief Rabbi of the wealthy 

 synagogue at Toledo. The Alphonsine Tables were first 

 printed in 1483 at Venice. 



The first notice of a remarkable aggregation of innumer- 

 able true nebulous spots, blended with stellar swarms, dating 

 from the middle of the tenth century, is in the writings of an 

 Arabian astronomer, Abdurrahman Sufi, a native of the Per- 

 sian Irak. The White Ox, which he saw shining with a 

 milky light far below Canopus, was undoubtedly the larger 

 Magellanic Cloud, which, with an apparent breadth of nearly 

 twelve lunar diameters, extends over a portion of the heav- 

 ens measuring forty-two square degrees. No mention is made 

 by European travelers of this phenomenon until the begin- 

 ning of the sixteenth century, although, 200 years earlier, the 

 Normans had advanced as far along the western coasts of Af- 

 rica as Sierra Leone (8 30' N. Lat.).f It might have been 

 expected that a nebulous mass of such vast extent, which 



* Cosmos, vol. iii., p. 91, and note, and 140, and note. 



t Prior to the expedition of Alvaro Becerra. The Portuguese ad- 

 vanced beyond the equator in 1471. See Humboldt's Examen Critique 

 de VHist. de la Geographic du Nouveau Continent, torn, i., p. 29.0-292 

 In Eastern Africa the Lagides had availed themselves, for purposes of 

 commerce, of the passage along the Indian Ocean, and, favored by the 

 southwest monsoon (Hippalus), had passed from Ocelis in the Straits 

 of Bab-el-Mandeb to the Malabar emporium of Muziris and to Ceylon 

 (Cosmos, vol. ii., p. 172, and note). Although the Magellanic Clouds 

 must have been seen in all these voyages, we meet with no record of 

 their appearance. 



