. .::." COLOUB OF THE SEA., 391 



solved in them. Perfectly pure water, like 

 pure air, when seen in bulk, appears of a beau- 

 tiful blue colour, but the least admixture of 

 foreign matter destroys this effect, and renders 

 the colour dirty and variously shaded. By 

 taking a glass tube, two inches wide, and 

 six feet six inches long, blackened internally 

 Vith lamp-black and wax to within half an 

 inch of the end, the latter being closed by 

 a cork, and filling it with chemically pure 

 water, putting at the bottom a few pieces of 

 white porcelain, and now holding the tube ver- 

 tically in a white plate we can develop the 

 naturally blue tint of water, and the column 

 of it acquires a beautiful pure colour of this 

 kind. Wherever water is clear and deep, it 

 has the colour natural to it. Professor J. 

 Forbes, in his travels in the Alpine regions, 

 says : " During an expedition which I made 

 upon the ice in the month of September, 

 during a snow-storm, I observed' that the 

 snow lying eighteen inches deep, exhibited a 

 fine blue at a small depth (about six inches) 

 wherever pierced by my stick. Nor could 

 this possibly be due to any atmospheric re- 

 flection, for the sky was of a uniform leaden 

 hue, and snow was falling at the time." Hence 

 it is probable that blue is the colour of pure 

 water. The exquisite blue colour of the glaciers 



