In April 1948 the «Institut de Physique du Globe, Strasbourg » has been carrying out a program of seismic work on important explosions in the Black Forest. Seismic waves were recorded by 21 stations mainly along the profile between Strasbourg and the Alps across the Elack Forest and the «Schwâbische Alb ». The authors describe the explosive charges (nature, position, etc.), the instruments and techniques utilized, the regional geology and the complete readings of the records. Evidence for the existence of four layers is shown : gneiss-granit : h1 = 2.4 km ; v1 = 5,63 km/s deep-granit : h2 = 17.7 km ; v2 = 5,97 km/s gabbro-basalt : h.3 = 10. 1 km ; v3 = 6,54 km/s peridotit : v4 = 8,15 km/s The basaltic layer is very well defined : the P. impulses are very clearly shown, also the reflections on the upper part of the intermediate layer. It appears that this layer formerly supplied the lava of the old volcanoes in southern Germany ; in this area the Mohorovici discontinuity is at a depth of about 30 kilometers. These results and the different wave-velocities obtained are discussed and compared with the previous ones. The studies of natural earthquakes in southern Germany differ partly from our results : the problem of «calculated depth of focus » requires further research work. A large bibliography concludes the paper.