132 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS 



of the lakes by means of standard solutions of copper and nickel sulphate and an 

 instrument devised from a stereoscope. By using measured amounts of the solu- 

 tions and mixing with pure water it was possible to match the water and to express 

 its color as an equation, from which the depth and shade of color might be at 

 any time reproduced. The solutions were prepared by dissolving 30 grams of the 

 chemically pure salt in 100 cubic centimeters of distilled water and were placed 

 in a thin glass" cell," with parallel sides, the inside measure of which was 

 8 millimeters. A reflector was so an-anged that the water could be viewed 

 dii-ectly, while the fluid mixture was seen by reflected diffused light. The proper 

 proportions could then be obtained by experiment. The shade of color changed 

 somewhat by the condition of the sky, the position of the observer, the time 

 of day, and the strength of the wind. In the case of Moraine Lake the depth 

 of blue was too intense in the quiet of the early morning to be matched by 

 the pure copper sulphate solution, in a cell of the above thickness. A slight 

 breeze sprang up and lightened the shade sufficiently. The table below gives the 

 color simply at the time of observation and under the conditions then prevailing. 



COLOR OBSERVATIONS UPON ROCKY MOUNTAIN LAKES. 



Proportions in cubic centimeters. Sky. 



29 c.c. green + lo c.c. blue + 6$ c.c. water. Clear but hazy, 

 ID c.c. green + lo c.c. blue + 50 c.c. water. Fair. 

 3 c.c. green + 30 c.c. blue + 23 c.c. water. Sunny. 



As the season advances a marked change occurs in the color of the water of 

 Lake Louise, there being much more blue in the lake in the early part of the sum- 

 mer and more green towards the fall. Mr. Robert Campbell informed me that a de- 

 cided change has occurred in the color of the vvater of Emerald Lake in the last 

 few years, it being more of an emerald when he first saw it and now he considers 

 it more of a turquoise. In discussing this change with Mr. Bell-Smith, the 

 Canadian artist, I learned that he had observed the same change since 1888, there 

 being a very noticeable increase in the amount of blue. 



Some simple observations and experiments in the field made clear to the 

 writer the cause of the differences in color of the water of different lakes and the 

 changes that occur in the same lake. It had been remarked before, but it was left 

 for Bunsen to demonstrate that absolutely pure water is blue, as seen by trans- 

 mitted light. 1 The colors with the longer wave-lengths, as yellow, orange, 



• " Ueber den innern Zusammenhang der pseudovulkanischen Erscheinungen Islands," Annalen der 

 Chemie und Pharmacie, Bd. LXii, 1847, p. i. Previous to the time of Bunsen the illustrious scientists, Newton 

 Humboldt, Davy, Arago, and Forbes had speculated upon the problem but with only meager results. Later 

 Beetz, Tyndall, Bezold, Boas, and Aitkin had more or less completely grasped the idea of selective absorption 

 and gave us a satisfactory theory of the various modifications of the color of water in nature. 



" Ueber die Farbe des Wassers, " von W. Beetz, Annalen der Physik und Chemie, Bd. cxv, 1862, s. 

 137 zu 147- 



The Glaciers of the Alps, chapter 6, Pt. 11, Color of Water and Ice, i860, Tyndall. 



Lectures on Light, Tyndall, 1877, p. 35. 



Theory of Color, Wilhelm Von Bezold. Translated by Koehler, 1S76, pp. 41 and 67. 



" On the Color of the Mediterranean and Other Waters," Aitkin, Proc. Roy. Soc. of Edinburgh, xi, 18.S2 

 pp. 473 to 4«3- 



