128 INORGANIC EVOLUTION. [CHAP. XV. 



with regard to the planetary nebulae. Nebulae generally we cannot at 

 present discuss with any advantage, because there are very many bodies 

 classed as nebulae in the different catalogues about the physical natures 

 of which we know absolutely nothing. I shall only call attention to 

 those points about which we can be most certain. 



Not only do we find stars and planetary nebulae increasing in 

 number as the Milky Way is approached, but the undoubted star clus- 

 ters also increase towards the Milky Way in a marvellous manner. 



BauschingerJ (1889) in a review of Dr. Dreyer's "New General 

 Catalogue" (7,840 objects), discussed the distribution of different 

 classes of objects and found that star clusters, by which he means of 

 course resolved clusters, and planetary nebulae congregate in and near 

 the galaxy. 



Mr. Sydney Waters some four years later, in 1893, brought 

 together the nebulae and the star clusters on maps which showed, in a 

 most unmistakable manner, that the star clusters, like the planetary 

 nebulae and stars generally, are very much more numerous in the plane 

 of the Milky Way than they are in any other part of the heavens. 



It is striking to note the fidelity with which the clusters follow 

 not only the main track of the Milky Way, but also its convolutions 

 and streams, while the remarkable avoidance of the galaxy by the 

 nebulae, excluding the planetary nebulae, is obvious ; it was indeed 

 noted by Sir Wm. Herschel. 



We have seen, then, that the greatest number of stars congregate 

 in the plane of the Milky Way, and the greatest number of planeta r y 

 nebulae and the greatest number of star clusters. 



* F. J. S. Ast. Ges., vol. xxiv, p. 43. 



