144 cosmos. 



the celestial river of the Arabs*), which forms almost a great 

 circle of the sphere, and is inclined to the equator at an an- 

 gle of 63°. The poles of the Milky Way are situated in Right 

 Ascension 12h. 47m., N. Decl. 27° ; and R. A. Oh. 47m., S. 

 Decl. 27° ; the south galactic pole therefore lies near Coma 

 Berenices, and the northern between PhcBnix and Cetus. 

 While all planetary local relations are referred to the eclip- 

 tic — the great circle in which the plane of the sun's path in- 

 tersects the sphere — we may as conveniently refer many of 

 the local relations of the fixed stars, as, for instance, that of 

 their accumulation or grouping, to the nearly complete circle 

 of the Milky Way. Considered in this light, the latter is to 

 the sidereal world what the ecliptic is to the planetary world 

 of our solar system. The Milky Way cuts the equator in 

 Monoceros, between Procyon and Sirius, R. A. 6h. 54m. (for 

 1800), and in the left hand of Antinous, R. A. 19h. 15m 

 The Milky Way, therefore, divides the celestial sphere into 

 two somewhat unequal halves, whose areas are nearly as 8 

 to 9. In the smaller portion lies the vernal solstice. The 

 Milky Way varies considerably in breadth in different parts 

 of its course.f At its narrowest, and, at the same time, most 

 brilliant portion, between the prow of Argo and the Cross, 

 and nearest to the Antarctic pole, its width is scarcely 3° or 

 4° ; at other parts it is 16°, and in its divided portion, be- 

 tween Ophiuchus and Antinous, as much as 22°.$ William 

 Herschel has observed that, judging from his star-gaugings, 

 the Milky Way would appear in many regions to have 6° or 

 7° greater width than we should be disposed to ascribe to 

 it from the extent of stellar brightness visible to the naked 

 eye."§ 



Huygens, who examined the Milky Way with his twenty- 

 three feet refractor, declared, as early as the year 1656, that 

 the milky whiteness of the whole Galactic zone was not to 



illuminating power, in reference to the very great inequality of the 

 light of the whole zone, during my long residence in the southern hem- 

 isphere, and which I have recorded in my journals. 



* The comparison of the ramified Milky Way with a celestial river 

 led the Arabs to designate parts of the constellation of Sagittarius, whose 

 bow falls in a region rich in stars, as the cattle going to drink, and to 

 associate with them the ostrich, which has so little need of water. (Ide- 

 ler, Untersuchungen uber den Ursprung und die Bedeutung der Stcrnna* 

 men, § 78, 183, and 187 ; Niebuhr, Beschreibung von Arabien, s. 112.) 



t Outlines, p. 529; Schubert, Ast., th. iii., s. 71. 



t Struve, Etudes d'Astr. Stellaire, p. 41. 



§ Cosmos, vol. i., p. 150 



