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The benefits to come from a more intensive study of water life are just beginning to be disclosed. These are least in amount in the well filtered water of springs, and greatest in the water of turbu- lent streams, flowing through fine soils.

It rises nearer to the surface at the height of the midsummer season and descends a few meters with the progress of the cooling of the autumnal atmosphere.

Further study of the thermocline has shown that it is not constant in position.

The illustrations, where not otherwise credited, are mainly the work of the junior author. Our bibliography, necessarily brief, includes chiefly American papers. Here is a rough statement of the dissolved solids in some typical waters : In rain water 30 40 parts per million In drainage water off siliceous soils 50 80 In springs flowing from siliceous soils 60 250 In drainage water off calcareous soils 1 40 230 In springs flowing from calcareous soils 300 660 In rivers at large 120 350 In the ocean 33000 37370 Thus the content is seen to vary with the nature of the soils drained, calcareous holding a larger portion of soluble solids than siliceous soils. Drainage waters from cultivated lands often contain more lime salts than do springs flowing from calcareous soils that are deficient in carbon dioxide.

Yet we have worked jointly on every page of the book. We have cited but a few comprehensive foreign works; the reference lists in these will give the clue to all the others. Spring waters are more highly charged than other drainage waters, because of pro- longed contact as ground water with the deeper soil strata.

Ifeedham The life of waters 3WN ROAD NEVADA 89701 QK96 Needharc 1& The life of inland waters 1927 FORESTA INSTITUTE OCEAN MOUNTAIN STUDIES 6205 FRANKTOWN ROAD CARSON CITY, NEVADA 19701 THE LIFE OF INLAND WATERS SEASONAL CHANGES ON SPRING FLOODS SUMMER SUNSHINE The view is from West Hill, looking across the head Field Station towards the THE RENWICK MARSH AT ITHACA AUTUMN FIRES WINTER FREEZING l of Cayuga Lake and the grounds of the Biological Campus of Cornell University. Such thermal stratification as the current permits is direct in summer and inverse in winter, and there are the same intervening periods of thermal over- turn when the common temperature approaches 4 C.

An elementary text book of fresh-water biology for students BY JAMES G. In summer and, in winter there is less "stagnation" of bottom waters owing to the current of the stream.

Sometimes it falls across two spaces and is rendered 1 ess apparent in the charting by the selection of inter- vals. The vertical spaces^ represent degrees Centigrade and the figures attached to the curves indicate the depths in meters. In the middle of August it lies above the 8 meter level, though it begins to descend later in the month.

Leaving aside the not unusual erratic features of surface temperature (repre- sented by the topmost contour line) it will be noticed that there is a wider interval somewhere between 8 and 1 6 meters than any other interval either above or below it. Temperature of the water at different depths in Lake Mendota in 1906.

At any rate, it appears certain that the thermocline marks the lower limit of the chief disturbing influences that act upon the surface of the lake.

Perhaps the thermocline is but an accumulation of such sort of thermal disturbance-records, ranged across the vertical section of the lake, somewhat as wave-drift is ranged in a shifting zone along the middle of a sloping beach.

Perhaps an occasional deeper mixing, extending to its lower boundary, and due possibly to high winds, might bring together successional lower level s of temperature of considerable intervals .