Previous History.—In 1892 Professor Carl W. S. Aurivillius published his well-known paper “Ueber einige ober-silurische Cirripeden aus Gotland” (Bihang Svenska Vet.-Akad. Handl. Bd 18, Aid. IV, No. 3). Besides the remarkable specimen from the Ludlovian Pterygotus bed of Wisby, to which he gave the name Pollicipes signatus, and a supposed fragment of a scutum, which he called P. validus, Professor Aurivillius described a number of “kurze, mehr oder weniger cylindrische, mit Schuppen bedeckte Bildungen”, which he regarded as the peduncles of a cirripede and referred provisionally, in the absence of any trace of a capitulum, to Scalpellum. Though all the specimens (except possibly of S. cylindricum) came from a single stratum, bed c of Lindström, probably contemporaneous with our Wenlock Shale, and though the majority were found in a single locality, Djupvik in Eksta, still Professor Aurivillius considered that he could with certainty distinguish the following seven species:

Two years ago, in discussing the thermal energy of the earth, I suggested that while it had become impossible to deduce the earth's age from its thermal condition alone, Kelvin's problem might profitably be reversed by accepting the earth's age as a known factor, and deducing with its help the thermal history of the earth. This paper is a first attempt to attack the new problem then suggested. For geological purposes, one of the most fundamental aspects of the problem is that relating to the depth within the earth's crust at which temperatures are attained such that, under suitable conditions of pressure, molten rock magmas may exist. The determination of the minimum depth of possible rock fusion is a first essential to any adequate theory of vulcanism, and indeed of igneous activity in general. It is not sufficient, however, to ascertain that depth for present conditions alone, its variation during the earth's geological history must also be investigated ; for if, as is generally believed, the earth is a cooling body, the depth must be slowly increasing, and in former periods it must necessarily have been nearer the surface than it is now. In the limiting conditions both of position and time, tlie depth of fusion may have been at, or so near as to be for all practical purposes at, the surface itself. That is to say, at the beginning of geological history the earth may have been in a molten condition at, or immediately below, the then existing surface

In descriptions of Recent and Tertiary Terebratulids at least, the type of folding is often hardly mentioned, and is left to be inferred from the figure, in spite of the fact that Douvillé in 1879 showed that it might be even of generic importance. Buckman has more recently drawn attention once more to the importance of this character and has shown that its due consideration may lead to fruitful results in classification. The object of this paper is to point out further cases in which it has been neglected.

In this zone the phenomenon of départ or leaching is carried to a finish, and though of little significance in the case of the gibbsitic laterites of the diabases, gabbros, and syenites, since these from the beginning of alteration in the zone of leaching have been deprived of the greater part of the elements to be removed, yet in the case of the mica-schists it is of great importance. But in every case there is an accentuation of a phenomenon already evident in the preceding zone, namely the emigration of iron towards the surface, where it becomes concentrated. At the same time concretionary phenomena, often resulting in the separation of the hydrates of iron and aluminium one from the other, become increasingly important and reach their maximum development quite close to the surface, where they lead to the formation of a resistant crust (cuirasse), in which hydroxide of iron acts as cement; this hydroxide may even become sufficiently abundant to constitute an ore of iron, particularly in the case of certain diabases, and above all of peridotites.