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stressed that the temperaturę of bottom deposits at the depth of 5—6 m is taken here into account. There are no temperaturę changes here during the year. This temperaturę aąuals approximately the average temperaturę of lakę waters above the bottom. It has been mentioned above that one measurement during the year is sufficient for this purpose.

With this assumption in mind in seven lakes of the Wielkopolsko-Kujawskie Lakę Distric thermic probings have been madę in bottom deposits up to the depth of 6—10 m during characteristic seasons. The results have confirmed the correst-ness of conclusions drawn for the Goplo Lakę. The most essential temperaturę changes of bottom deposits occur in the layer of 0—3 m. At the depth of 5—6 m already the deposit temperaturę in the particular lakes during the year does not change and eąuals from 8.3°C in the amall interforest Czarne Lakę to 10.5°C in Lakę Wikaryjskie.

Even so modest exploration data like these allow make a ranging of the ex-plored lakes in dependence on their morphometric character (mainly surface and depth). In the years 1971—1972 temperaturę measurements of bottom deposits have been taken in the warmed up Lakę Pątnowskie. Here at the depth of 5 m a relatively great temperaturę changeability has been found from 12.3 to 13.0°C. This is probably the result of a differentiated thermic structure of the lakę which is within the cooling circulation of the power station.

TransJated by Bożena Bieszk

THSTYTTTT GEOGRAFII

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