Up to the year 1000 the German home had its fireplace in the center. The smoke escaped through a big hole above, which was covered by a second roof that kept the rain out. Light got in as best it could. The West-phalian home in which I was born was still of that kind, like a hundred thousand other North German peasant dwellings. In the oldest times a few holes were also cut into the sides of the house. My people, however, had small glass windows, but then I was bornin 1830— after Christ, you know. Wood and peat were exclusively used until the end of the twelfth century; coal is mentioned. The first information comes from Lüttich (Liège). In the fourteenth century coal was used in Aix-la-Chapelle; in 1429, about the river Saar. Since that time, but never like the present, was the air filled with carbon dioxid, sulphurous