300 



VOYAGE TO THE POLAR SEA. 



April 



Consequently when the sun is between fourteen and 

 twenty-three degrees in altitude, the refraction of its 

 rays is set forth with the greatest effect, and snow- 

 blindness has to be guarded against. In the bright 

 arc, while each tiny prism displays its complete set of 

 colours, the red tint is the most prominent nearest to 

 the sun, the purple lying on the outside indistinctly 

 defined. 



DIAMOND DUST. 



c The iridescent hues illuminating the high cirro- 

 cumulus clouds or mackerel sky, which occasionally 

 favour us, present even a more wondrous effect of 

 colouring. Each minute crystal component of the 

 clouds, within a radius of about twenty-two degrees 

 around the sun, displays all the tints of the spectrum ; 

 the vast quantity of colouring, blending softly and har- 

 moniously together, is so intermixed that it is difficult 

 to determine which hue predominates at any one point 



