Dr. Charles Doolittle Walcott acquired a taste for geology and natural history when very young. As a schoolboy he made large collections in the region of his home, and determined to follow a scientific career if possible.

A British Museum official may perhaps be pardoned if, in a review of the progress of mineralogy since the first appearance of the Geological Magazine, he begins with a reference to scientific work done in the Museum with which the Editor was so long associated. At the time when the Magazine first saw the light the Keeper of the Mineral Department was the late Professor Nevil Story-Maskelyne. He was one of the first to grasp that efficient tool for deciphering mineral aggregates which had been provided by Nicol and Sorby in the thin-section. He was engaged in the particular work to which Keepers of that Department have since appeared to consider they must in duty bound devote much of their time and energy, viz. the investigation of meteorites, and, assisted by the microscopic examination of thin slices of these bodies, he was soon able to announce the discovery in them of several new species, one of which, the sulphide of calcium, oldhamite, must have been formed under conditions very different from those which prevail on the earth's surface.

The formation of a new Government organization to foster and promote the interests of the Mining Industry of the United Kingdom has been recently proposed in two distinct quarters. The Coal Conservation Committee of the Ministry of Reconstruction, which issued its report (Cd. 9084) early in the past year, recommended the establishment of a Ministry of Mines and Minerals, to be presided over by a Minister with a seat in Parliament; while in a report to the Minister of Munitions, issued as a white paper (Cd. 1984) on November 15, Sir Lionel Phillips, late Controller of the Department for the development of Mineral Resources in the United Kingdom, favours the setting up of a Mines Department, to be attached to one of the existing great Departments of State.

When I received the invitation to open this discussion my first feeling was of diffidence, for, the interior of the earth being necessarily inaccessible to direct observation, the solution of the problems connected with it has principally been left to mathematical research, and this must remain the final court of appeal. In these circumstances it seemed verging on presumptuousness to address an audience consisting so largely of mathematicians in inauguration of a discussion on the interior of the earth. Second thoughts showed that there was much to he said against this view, for, though mathematics is the court of appeal, it can only decide on the facts placed before it by the sciences of observation, and so the discussion seems profitably prefaced by a statement of the leading facts which have been collected, and those conclusions which are so directly derived from them as to have almost the validity of observation.

The following notes were compiled, for the most part, some years ago, but their publication in the present form suggested itself to the writer on the perusal (during a short “leave” from active service) of a number of recent papers ou Ammonites, principally Professor Swinnerton and A. E. Trueman's study of the “Morphology and Development of the Ammonite Septum”. The main part of that inquiry is devoted to the development of the septum, illustrated by successive “septal sections”, and it is claimed that where sutural development cannot be worked out, “septal sections” will to some extent serve as a substitute. The writer lias no intention of discussing the usefulness of “septal sections”; but some of the suggestions put forward, and conclusions arrived at, by the authors, as well as certain opinions, whicli they adopt from other workers on Ammonites, invite critical examination. Since, in the present paper, other recent work on the morphology and physiology of the Ammonite septum and suture-line, not yet embodied in textbooks, is also included, and since the writer ventures to put forward opinions that differ in many essentials from the views of both textbooks and other authors, it is hoped that the paper may prove of general interest.