Above Stralau the river is polluted by numerous manufactories and washing establishments, and by the effluent from a considerable part of the city’s extensive sewage farms. The shipping on this part of the river also is heavy, and sewage from the boats is discharged directly into the river. The average number of bacteria in the Spree at this point is something over ten thousand per cubic centimeter, and 99.6 per cent of them were removed by the filters in 1893. The watershed of the Spree above the new water-works at Müggel I found by map measurement to be 2800 square miles, and the low water-discharge is said to be 269 million gallons daily. The river at this point flows through Lake Müggel, which forms a natural sedimentation-basin, and the raw water is quite clear except in windy weather. There were 16 towns on the watershed with populations above 2000 each in 1890, and an aggregate population of 132,000, which does not include the population of the smaller places or country districts. None of these places purify their sewage so far as they have any. Fürstenwalde with a population of 12,935, and 22 miles above Müggel, has surface sewers discharging directly into the river. Above Fürstenwalde the river runs through numerous lakes which probably remove the effect of the pollution from the more distant cities. There is considerable shipping on the river for some miles above Fürstenwalde (which forms a section of the Friedrich Wilhelm Canal), but hardly any between Müggel and Fürstenwalde. The raw water at Müggel contains two or three hundred bacteria per cubic centimeter, and is thus a comparatively pure water before filtration. It is slightly peaty and the filtered water has a light straw color. Lake Tegel, which supplies the other part of the city’s supply, is an enlargement of the river Havel. The watershed above Tegel I find to be about 1350 square miles, and the annual rainfall is about 22 inches. The low water-discharge is said to be 182 million gallons daily, and the city is allowed by law to take 23 million gallons for water-supply. There were ten towns upon the watershed with populations above 2000 each in 1890, and with an aggregate population of 44,000. Of these Tegel is directly upon the lake with a population of 3000, and Oranienburg, 14 miles above, has a population of 6000 and is rapidly increasing. The shipping on the lake and river is heavy. The lake water ordinarily contains two or three hundred bacteria per cubic centimeter. The lake is shallow and becomes turbid in windy weather.