A Splendid map of South Africa published by the Geological Survey of the Union has just reached me. Few will hail it with more pleasure than myself, for I know the country well, having spent fifteen years in helping to unravel its geology. This map marks a great advance on previous geological sketch-maps. To future workers it will be a great boon.

About Easter, 1925, I noticed the curious course of the streams through the big deltas of Measand on Haweswater, and of Aira Beck on Ullswater. Both these streams, after having traversed about half the radial length of the delta, turn fairly sharply towards the head of the lake. This turn in such a pronounced degree is contrary to what one would expect.

Recently a mechanism allowing the escape of the heat generated by radioactivity in the basaltic under-crust of the earth has been proposed by Dr. Holmes, and a very similar one by Dr. Joly has gained wide attention. In these theories the excess heat generated by radioactive changes is supposed to be dissipated by an alternate fusion and solidification of the basaltic magmas assumed to make up the lower levels of the outer crust, the heat escaping through the floor of the oceans during so long a period of time that while, in the aggregate, the amount of heat thus passed out is very great, yet at no time is the temperature of the oceans sensibly affected.

It is quite clear that Professor Joly's presentation of his theory of basaltic cycles is, taken alone, far too simple to match the complex details of geological history. In a former paper I attempted to extend the principles he has so persuasively advocated, by adding the conception of a peridotite cycle of longer period, and I was careful to point out that even this extension led to no more than a rough approximation to the actual realities of the earth's behaviour. As soon as details are considered, the pursuit of the subject leads its explorer into a maze of difficulties, because of the many interfering factors that must also be taken into account. Nevertheless, a broad survey of the earth's history suggests that Joly has surmised what is so far the only kind of process that even begins to correspond with the dominant facts. And that, without any qualification, is a very great achievement.