THE arrangements for the experimental explosions next month in France (NATURE, vol. 113, p. 135) are now practically complete.1 They will be carried out by the military services, though details as to time, etc., have been settled by a committee on which various scientific bodies are represented. There are to be three main explosions, in each of which rather more than ten tons of explosives will be fired on the surface of the ground. The site of the experiments is to be the neighbourhood of La Courtine, about forty miles west of Clermont-Ferrand, and the explosions will be made at three different points about one-third of a mile apart, the centre of the triangle formed by them being in lat. 45° 44-8′ N., long. 2° 14-7′ E. The times have been chosen so that the experiments may be made under different meteorological conditions, the first on May 15 at about 19 h. 30 m. civil time, the second on May 23 at 20 h., and the last on May 25 at 9 h.