Geological Sketches

Abstract

No better idea can be given of this little book than is obtained from the first few words of the preface. “This edition of the ‘Geological Sketches’ offers nothing new to the public. Taken in connection with the former one, it only presents in a permanent form and in their original sequence all the geological and glacial papers contributed by Prof. Agassiz to the Atlantic Monthly during a number of years.” It consists, in fact, of five chatty papers on glacial phenomena in various parts of the world, written in that kind of personal manner that makes them read like a book of travels or a chapter of an autobiography. It is perhaps chiefly from this latter point of view that this collection is interesting. Whatever may be Agassiz's position with respect to the interpretation of the phenomena of recent glaciers, there can be no question but that to him is due the first recognition of their former. existence and extent in this country and elsewhere where they now no longer exist. From the day of that discovery in 1840, “Glacial Geology,” now a department by itself, has been steadily growing, till investigations into the work of ice has been carried into almost every part of the globe, not excluding the Tropics. Agassiz has therefore a fair right to the title of Father of Glacial Geology. He gives us here an interesting sketch of his first opening up this ground by his visit to Scotland, and puts in a popular form his theory of the formation of the parallel roads of Glen Roy. We have a glimpse of his well-known tone of thought in the question which he says, in one of these essays, one naturally asks, “What was the use of this great engine set at work ages ago to grind, furrow, and knead over, as it were, the surface of the earth?” and finds as an answer that it was a special provision for making the surface fertile by ploughing it deeply and preparing it as a grain-growing soil. Perhaps we could not have a better justification for calling tele-ological arguments “barren virgins,” with Prof. Huxley, than this instance, for if the glacial period were a special provision for the wants of man, we should be cut off from the conclusions, now almost proved by evidence, first that man existed in these isles before the glacial epoch, and second, that this epoch should rather be called the last glacial epoch, as there have been similar ones throughout geologic time. This last conclusion, involving the extension of glacial conditions through a long range of time, at various intervals, a conclusion largely due to Prof. Ramsay, will be only second in importance, when fully established to its extension in space so conclusively proved by Agassiz and others. The longest of the five papers in this collection is the most recent: “On the Physical History of the Valley of the Amazons,” in which he gives his reasons for considering the whole of that valley to have been filled with ice, and to have extended much further to the east at that period. This is scarcely the place for discussing conclusions that have been made known in a larger work with the evidence stated; but we may call attention to the fact that no furrows, striæ, or polished surfaces are anywhere to be found there, and the evidence, therefore, is not of that positive character that so remarkable a conclusion would seem to demand. The country is so little known that at any time fresh observations might modify any conclusion drawn from negative or secondary evidence.

Geological Sketches.

L.

Agassiz

By. Second Series. 8vo. pp. 229. (Boston, James R. Osgood and Co.; London, Trübner. 1876.)