MR. J. NASMYTH ON THE PLANET MARS. 305 



reflecting telescope, as contrasted with the view furnished 

 by the aid of a very fine 8 -in. aperture achromatic telescope 

 by Cooke, of York, I was much impressed with the superior 

 distinctness with which the tints of the relative portions of 

 the surface of the planet were brought out by the reflecting 

 telescope as compared with the achromatic. Although the 

 definition of the planet was as perfect as could be desired 

 when seen by the latter instrument, the markings on the 

 surface of the planet could only be distinguished by their 

 variety (or dificrence) of relative shade or brightness, while 

 in the view furnished by the reflector the actual tints or 

 colours of the various features were rendered quite distinct. 

 This was most prominently the case in respect to the 

 blue-green of the supposed sea (?) and the ruddy tint of 

 the land (?) and island (?). As before said, the snow-patch 

 on the south pole was rendered peculiarly distinct and de- 

 finite by the presence of a remarkable dark local shade im- 

 mediately surrounding it. In all these respects the draw- 

 ing is as faithful a representation as such a means can 

 enable me to accomplish. 



In respect to the cause of the superior manner in which 

 the various tints of the features of the planet were rendered 

 by the reflecting as compared with the achromatic tele- 

 scope, I am disposed to assign it to the fact that in the case 

 of the employment of a reflecting telescope the light from 

 the planet suficrs no change or decomposition in its passage 

 to the eye. Although some of the light is lost by reflec- 

 tion, yet the integrity of its original composition is main- 

 tained, and it reaches the eye of the observer in its original 

 virgin state ; whereas, in the case of the employment of 

 an achromatic telescope, the light does, to a certain extent, 

 suffer decomposition, and its recomposition is not altogether 

 perfect. Certain it is, that the difference in the manner in 

 which the tints of the features of the planet were brought 

 out was most strikingly evident in the case of the view 



SER. III. VOL. II. X 



