THE Second Plenary World Power Conference which was held at Berlin on June 16–26 was probably one of the most ambitious and one of the most elaborately staged international meetings of recent years, and it is difficult on that account to follow with accuracy the main lines of development which were traced throughout the discussions. In the first place, the weight of documentary material was very large. Prior to the opening of the Conference, about 390 papers submitted by 37 or 38 countries had actually been printed and were available for examination; but during the Conference itself a number of additional papers appeared, mostly from Germany and Austria, with the result that the official collection will probably be rather more than 430. In addition to that, the principal scientific and technical associations in Germany and Austria, and, to some extent also, Russia, had prepared special monographs surveying the position in their respective territories. These monographs did not form an intrinsic part of the Conference, but they should be considered as an additional contribution to the information collected.