THE first of the French experimental explosions took place, as arranged, on May 15 at 7.30 P.M. (summer time). Ten tons of melinite, contained in 64 barrels, were exploded simultaneously, forming a crater more than 60 feet wide and nearly 20 feet deep. Observers at a distance of 600 yards were inconvenienced by the air pressure in their ears. Of a number of animals that had been placed in pits not more than 50 yards from the source, a guinea-pig was killed, the rest were unhurt. The first results are said to be disappointing, but the success or failure of the experiment cannot be decided at so early a date. The explosion was heard at Bordeaux (152 miles) at 7.43-7.47. Taking the earlier time, the velocity of the sound-waves would be about 1029 ft. per sec., a value less than the normal velocity in air but somewhat greater than the maximum value (978 ft. per sec.) obtained for the Silvertown explosion of January 19, 1917. At the village of La Courtine, less than four miles away, only a slight shock was felt, but the vibrations are said to have been recorded at Montpellier (167 miles) and Strasbourg (329 miles). As the latter distance is more than a hundred miles in excess of the greatest distance at which the Oppau explosion was registered, some good estimates of the velocities of the condensational and distortional waves in the superficial layers should be obtained. The remaining explosions take place in the same district on May 23 at 8 P.M. and May 25 at 9 A.M. (summer time).