1. In the teaching of hydrodynamics many points of difficulty arise, both for teacher and for student. The subject abounds in subtleties even in its very elements, and the advanced student frequently finds himself in a state of doubt as to fundamental questions which crop up unexpectedly in connection with various problems. The following notes contain a discussion of a few of these fundamental matters: for example, they deal with some theorems of energy which have been found difficult by students, perhaps mainly through want of perfectly explicit statement of their scope and purpose. Finally will be demonstrated a theorem of vortex-motion, particular cases of which have been given by various writers, but which I have not seen stated elsewhere in the same generality. This will be found to lead to Lord Kelvin's well-known and far-reaching theorem of circulation, and to other theorems of the vortex-motion of a perfect fluid, some of which are already known.

Since the time when Agassiz and Buckland made known the former presence of glaciers in the mountain valleys of North Wales, much has been written concerning the glaciation of Snowdonia, but comparatively little attention has been given to that of Western Carnarvonshire. This part of the country stretches south-westwards as the broad promontory of Lleyn between Carnarvon Bay and Cardigan Bay. Western Carnarvonshire for the most part lay outside the paths followed by the native glaciers. None of the larger valleys of Snowdonia trend in this direction, and so the marks of recent glaciation are not so fresh and striking in this region as they are further east. Hitherto no one has attempted to give any detailed account of the Drift deposits over the whole of Lleyn, but various references to the glaciation of the region are found scattered in the literature dealing with the geology of Wales.

The anatomy of all marine mammals presents an interesting field of observation upon their structural adaptation to a particular environment, and naturally, therefore, an extensive literature already exists in respect to these mammals, notwithstanding the many difficulties connected with their detailed examination. Their large size and the rapidity with which their tissues undergo decomposition have been serious obstacles in the way of prolonged dissection both of Cetacea and of Seals. Consequently, the examination of many parts of their anatomy has, of necessity, been more or less hurried. Accordingly, in the course of the preparations for the Scottish Antarctic Expedition, led by W. S. Bruce, LL.D., etc., arrangements were made for the preservation of mammalian specimens by the same injection methods that are now commonly used for the practical study of human anatomy, and the medical officer to the Expedition received practical instruction from myself in the application of these methods.

Since the report on the Hydroids collected by the Scotia was completed, almost three years ago, I have had an opportunity, thanks to the kindness of Dr W. S. Bruce, of looking through the enormous mass of material brought together by him during his Antarctic voyages. The search, begun in the hope of finding a few minute species—which, since many are epizoic on other forms of marine life, might readily be overlooked on cursory examination—has resulted in the addition of no less than 25 forms to the 36 already recorded. Deducting from this total of 61 forms two varieties, it appears that the Scotia collection contains in all 59 distinct species. Few, indeed, of these have been obtained in truly Antarctic latitudes—subantarctic or temperate seas having furnished the greater number—but this result is in accordance with the findings of the majority of the recent Antarctic expeditions. Dr Billard, in summarising the results of the Belgian, Swedish, and French expeditions, states that the known Hydroid fauna of Antarctic regions comprises only 32 species. But from his list he has, I think unjustly, excluded South Georgian records. His list, moreover, published before the valuable paper by Professor Hickson and Mr Gravely on the Discovery Hydroids was issued, necessarily makes no reference to the large number of forms recorded by them from Victoria Land.

Having been struck by the evident importance of Antarctic phenomena in relation to the climatic condition of lower latitudes, I have endeavoured in the following discussion to give a complete representation of these conditions, and to trace their bearing on the climate of sub-Antarctic and temperate zones. It is only now that sufficient data are available for such a purpose. I have been singularly fortunate, not only in the opportunities which I have had for obtaining access to valuable data, but also in the possession of that “practical” knowledge which has resulted from my two years' residence in the Antarctic. In any discussion of this nature it is obviously an immense advantage to have studied in the field the conditions there obtaining. This I have been able to do also for the Arctic during two voyages undertaken for this specific purpose, thereby being enabled to appreciate the great diversity in the fundamental conditions affecting the meteorology of the two Polar regions.

In my paper on “The Meteorology of the Weddell Quadrant and Adjacent Areas”(Trans. Roy. Soc. Edin., vol. xlvii. p. 103) data referring to temperature, pressure, cloud, and wind force were given for the stations of Ancud and Point Gallera on the coast of Chili. Since the above paper was communicated to the Society the reduction of the observations taken thrice daily at the Chilian coastal stations has been proceeded with, the observations utilised being published in extenso in the annual volumes issued since 1899 by the Maritime Department of the Republic of Chili. On the completion of the analysis of the tri-daily wind observations at Ancud and Point Gallera some features of considerable interest presented themselves, the most marked being the pronounced monsoonal character of the winds at the latter station—a condition which, as we will see later, holds good between the parallels of 33° and 40° of south latitude along the Chilian littoral. Table I. shows the monthly percentage frequency of the winds at Point Gallera. a lighthouse situated in lat. 40° 01' S. and long. 73° 44' W., for the seven years 1899–1905.

The present paper is based on the study of a suite of fossils collected in 1898 by Dr W. S. Bruce, during a cruise with Major Andrew Coats in the Barents Sea, on board the yacht Blencathra.

The fossils were found in situ in a cliff at the extremity of Cape Cherney, a promontory situated on the west coast of Southern Nowaja Semlja, in Iat. 70° 49' and long. 56° 37'. Contrary to what often obtains in the case of materials collected by explorers, they are all from the same bed, a fact which greatly increases the value of the collection, as there is thus no possibility of a mixing of forms from different horizons.

Through the courtesy of Dr W. S. Bruce, the leader of the Scottish National Antarctic Expedition, and of the late Professor D. J. Cunningham, the skeletons of the seals collected in the Antarctic during the voyage of the Scotia have been placed in my hands for study, and I wish to express my gratitude to these gentlemen for their great kindness in placing all the necessary requirements at my disposal. I also wish to state that Dr Bruce has given to the Museum of the University of Edinburgh a choice of the various skeletons, which, together with the specimens already obtained, will form a comprehensive and almost unique collection of the Antarctic seals.