208 Clusters and Nebulce. 



similarly divided galaxy in its construction. " Can it then be," 

 he asks, " that we have here a brother-system bearing a real 

 physical resemblance and strong analogy of structure to our 

 own V But what an astonishing disclosure of a spiral convo- 

 lution has here been made by the 6-foot mirror of the Earl of 

 Eosse is now so well known through the multiplication of 

 representations (not all of them, it may be feared, much like 

 the original !), that it need not be enlarged upon here. Our 

 readers will, however, be glad to be made acquainted with that 

 great observer's comments. After having remarked that 

 Herschel II.'s figure of the partially split ring, taken with a 

 "front-view," and therefore reversed right and left only, 

 requires to be inverted also before it will correspond with the 

 Newtonian image of his reflector, he proceeds, " We thus 

 observe that with each successive increase of optical power 

 the structure has become more complicated and more unlike 

 anything which we could picture to ourselves as the result of 

 any form of dynamical law of which we find a counterpart in 

 our system. The connection of the companion with the greater 

 nebula, of which there is not the least doubt, and in the way 

 represented in the sketch, adds, as it appears to me, if possible, 

 to the difficulty of forming any conceivable hypothesis. That 

 such a system should exist, without internal movement, seems 

 to be in the highest degree improbable : we may possibly aid 

 our conceptions by coupling with the idea of motion that of a 

 resisting medium ; but we cannot regard such a system in any 

 way as a case of mere statical equilibrium. Measurements, 

 therefore, are of the highest interest, but, unfortunately, they 

 are attended with great difficulties. Measurements of the 

 points of maximum brightness in the mottling of the different 

 convolutions must necessarily be very loose ; for although on 

 the finest nights we see them breaking up into stars, the 

 exceedingly minute stars cannot be seen steadily, and to 

 identify one in each case would be impossible with our pre- 

 sent means.'''' The central nucleus he saw clearly resolved 

 with his smaller speculum of 3 feet in diameter, and the 

 6-feet showed the spirality of the principal nucleus very plain, 

 and a spiral arrangement in the smaller nucleus, and he 

 thought that considerably less power would suffice on a 

 very fine night to bring out the principal convolutions. 

 Accordingly this impression has been verified by Secchi, who 

 with 9^ inches of aperture in the Eoman sky was able to attest 

 the great accuracy of the Earl's representation. He succeeded 

 in tracing very fairly the two branches of the spiral, and in 

 detecting many stars ; but whether in, or only in front of, 

 the nebulosity, he leaves undecided. He has noticed it as a 

 peculiarity that it will not bear magnifying power. Ilis mea- 



