. Science . considerations. The as-sumption that because Pyramid Lake may beand probably is a remnant of Lake Lahontan,which has never been dried up completely,therefore its salines are an index of the ageof the whole larger lake seems to me errone-ous. A conception of a closer interpretatioamay perhaps be obtained in the following one doubts that Lake Lahontan formerlyrose to a height of approximately 500 feetabove present Pyramid Lake and that its 1 Published by permission of the Director of theUnited States Geological Survey. 210 SCIENCE [N. 8. Vol. XLI. No. 1049 waters have since la
. Science . considerations. The as-sumption that because Pyramid Lake may beand probably is a remnant of Lake Lahontan,which has never been dried up completely,therefore its salines are an index of the ageof the whole larger lake seems to me errone-ous. A conception of a closer interpretatioamay perhaps be obtained in the following one doubts that Lake Lahontan formerlyrose to a height of approximately 500 feetabove present Pyramid Lake and that its 1 Published by permission of the Director of theUnited States Geological Survey. 210 SCIENCE [N. 8. Vol. XLI. No. 1049 waters have since largely disappeared throughdiminishing water supply. The water supplythat maintained the larger lake, as that whichmaintains the smaller lakes of the presentday, came principally from a few majorstreams draining from the higher Sierra. Ofthese Truckee, Carson and Walker rivers werewith little doubt, the dominating factors. Thefollowing is an outline map showing the gen-eral relation of these drainage Outline Map Showing Truekee-Pyramid DrainageSystem and its Former Northward Extension. Approximate equilibrium was maintained inthe larger Lake Lahontan through the balanceof evaporation and inflow. Evaporation variesdirectly with the surface area of the waterbody. Inflow is supposed to have been grad-ually decreasing as the lake level was , however, the waters fell to the level of any divide which would separate the basin intotwo or more distinct parts, the equilibriumthat had been maintained for the lake body asa whole would hardly be continued in exactlyproportionate relations in the two separatedparts. Each part must have then establisheda new relation of separate inflow and evapora-tion ratio, and it is almost a certainty that anoverflow would for a time be established fromone side toward the other over the intermediatedivide. Such an overflow may have occurred over theFernley divide from the Truckee Basin into theCarson Basin. The evidence of channels ther
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