In no portion of Lake Tahoe did I observe any of the green tints, except where the light-colored bottom was visible.

This was, probably, owing to the circumstance that no considerable quantity of suspended matter existed in any of the waters observed.
_Rhythmical Variations of Level in Lakes: or "Seiches."_--As might be expected, the waters of Lake Tahoe are subject to fluctuations of level, depending upon the variable supplies furnished by its numerous affluents.

In mid-winter, when these streams are bound in icy fetters, the level falls; while in the months of May and June, when the snows of the amphitheater of mountain-slopes are melting most rapidly, the level of the Lake rises, and a maximum amount of water escapes through its outlet.

According to the observations of Capt.

John McKinney, made at his residence on the western shore of this Lake, the average seasonal fluctuation of level is about 0.61 of a meter; but in extreme seasons it sometimes amounts to 1.37 meters.