446 



NATURE 



[March io, 1898 



minutes (Fig. 6) Considered as pictures, the drawing is perhaps 

 more attractive than the photograph, but this is because the 

 photograph has been enlarged to such an extent that the grain 

 of the film is shown. The comparison should be made between 

 the original negative and the drawing, in order to be able to 



relative position in the two pictures, when considered! with 

 reference to the great nebula. The diflTerence may indicate 

 a change in the direction of the axis between 1847, when the 

 drawing was made, and now, but it would be unwise to conclude 

 that this difference is real, seeing that the distinct statement is 



-From a drawing, 



F"rom an enlarged photograph by Mr. W. E. Wilson. 



The Spiral Nebula in Canes Venatici. 



appreciate fully the assistance given by photography to the 

 delineation of the s-tructure of the nebula. 



The Andromeda Nebula. 



Until Dr. Roberts took the photograph of the nebula of 



Andromeda in 1888 (Monthly No/ices A'.A.S., vol. xlix. p. 65, 



1888-89), astronomers did not understand that this object was a 



remarkable example of the ring-stage in celestial evolution. 



made that " the lithograph represents somewhat inaccurately 

 the relative positions of the chief nebulous centres of conderrs- 

 ation" {Annals of Harvard College Observatory, 1876). But 

 though this possible change is important in itself, it is not so 

 instructive as the rings of nebulosity seen surrounding the bright 

 central portion of the great nebula on the photograph. The 

 dark lanes drawn by Bond are seen upon the photograph to be 

 divisions between thezonesof nebulous matter ; and what visually 



Fig. 7. — The Andromeda Nebula. (From a drawing by Bond and 

 Tiouvelot.) 



Fig. 8.— The Andromeda Nebula. (From a photograph obtained by Dr. 

 Roberts, with an exposure of ninety minutes.) 



Bond's drawing (Fig. 7) was acknowledged to be the finest 

 representation of the nebula, but how much it is inferior 

 to the photograph (Fig. 8) is shown in the accompanying 

 comparison of the two. It will be seen that the major axis 

 of the small nebula near the top on the right has a different 



NO. 1480, VOL. 57] 



appears to be accidental and enigmatical vacuities, are shown 

 photographically to be the consequences of cosmogonical action. 

 The hypothesis of the formation of worlds from nebulse was 

 thus confirmed, if not demonstrated, by the discovery of this 

 new link to connect celestial species. 



