Notices respecting New Books. 385 



The catalogue is followed by a chapter on the law of Distribution 

 of Nebulas and Clusters over the surface of the Heavens. After 

 giving a table showing the number of these objects observed in each 

 hour of RA in the northern catalogue, the author observes, " It is 

 evident from this that the great mass of the nebulcC visible in our 

 latitudes is accumulated upon the 6 hours of RA between 9"* and 

 15*^; on both sides of which the falling off is rapid, and after \5t^ 

 very sudden; while within the 6 hours in question the condensation 

 increases to a very marked maximum between the hours 12 and 13." 

 (Between 12'^ and 13'^ the number in the catalogue is 441 ; between 

 15'' and IS'' it is only 42.) In order however to obtain a better 

 view of the mode in which they are grouped, and a measure of their 

 condensation, he projects them on a chart, adopting a mode of pro- 

 jection by which equal areas on the sphere are represented by equal 

 areas on the chart. On this principle he constructed charts repre- 

 senting the northern and southern hemispheres divided into zones 

 of 3" in breadth or polar distance, and into hours of RA (subdi- 

 vided into quarters), on which he laid down the nebulae from the 

 contents of both catalogues, so as to obtain a coup-d'ail of their 

 distribution over the whole heavens. The principal conclusions 

 arrived at by this laboi-inus mode of proceeding are the following: — 



" 1st. The distribution of the nebuize is not, like that of the Milky 

 Way, in a zone or band encircling the heavens, or if such a band 

 can be at all traced out, it is with so many interruptions, and so 

 faintly marked out through by far the greater part of its circum- 

 ference, that its existence as such can be hardly more than suspected. 



" 2adly. One-third of the whole nebulous contents of the heavens 

 are congregated in a broad irregular patch, occupying about one- 

 eighth of the whole sui'face of the sphere ; chiefly (indeed almost 

 entirely) situated in the northern hemisphere, and occupying the 

 constellations Leo, Leo Minor, the body, tail, and hind legs of 

 Ursa Major, the nose of the Camejopard, and the point of the tail 

 of Draco, Canes Venatici, Coma, the pi'eceding leg of Bootes, and the 

 head, wings, and shoulder of Virgo. 



" 3rdly. Within this area there are several local centres of accu- 

 mulation where the nebulpe are exceedingly crowded, viz. 1st, from 

 59° to 62° of NPD in the 1 3th hour of RA between the northern 

 part of Coma and the fore legs of Chara, as also (in the same hour) 

 from 72° to 78° NPD between the palm branch and the northern 

 wing of Virgo ; and again, in the same hour, from 80° to 87° NPD 

 in the northern wing and breast of Virgo. Northward the nebulous 

 area terminates almost abruptly with a very rich patch between the 

 nose of the Camelopard and the tail of Draco. The line of greatest 

 condensation connecting these most condensed patches is irregular 

 and wavy, without appearance of reference to any one particular 

 centre, and the shading off, though patchy, is on the whole gra- 

 dual."— P. 135. 



After some further remarks on the distribution of the nebuliE in 

 the northern hemisphere, he tlius proceeds : — 



" In tiic southern a much greater uniformity of distribution pre- 

 Phil. Mag. S. 3. Vol. 32. No. 2 1 6. Mai/ 1 848. 2 C 



