Page images

-as I well know it has led many a beginner to suppose, what I believe occurs only in rare cases easily explained, that marine shells are found in the typical deposit of the drift period. The matter is no doubt left in this shape because of an early bias unconsciously fostered by Sir Charles in his effort to explain all the drift phenomena in consonance with his favorite iceberg hypothesis.

I may cite an additional instance, which, among other points, is perhaps indicative of the author's limited acquaintance with the exact history of the progress of geologic inquiry. He says. (p. 160): "It was first pointed out by Professor Ramsay, in 1862, that lakes are exceedingly numerous in those countries where [in which] ..... signs of ice-action abound." Unless he mean that Mr. Ramsay, in pointing out this fact several times, did it first in 1862, the statement is erroneous. In reality, the fact was distinctly indicated by Professor Emmons some twenty years earlier, and repeated by him in 1858. The sentence, however, is ambiguous; still, the meaning probably is: Professor Ramsay was the first to point out, in 1862, etc. Without presuming that Professor Ramsay borrowed, I wish simply to suggest that he was anticipated by Dr. Emmons, and that Sir Charles is doubtless ignorant of the fact—a point easily understood by such as are intimately acquainted with the history of American Geology.

An example of the author's lack of accuracy, both from ambiguity and from defective statements, I take from p. 2. Speaking of the earth's crust, which he seems to divide into two parts, (1) what "is accessible to human observation," and (2)" the whole of that outer covering of the planet on which we are enabled to reason by observations made at or near the surface," he proceeds to say: "These reasonings may extend to a depth of several miles, say ten miles." Now, according to the language used, he appears to affirm that some ten miles embrace all those parts of the earth's crust respecting which one may reason from observations. made at or near the surface. But, waiving this ambiguity,

and supposing that he means that the thickness of what is accessible to human observation is about ten miles, one may still demur, and think that the statement is made from very old estimates, and not in the light of present knowledge. The fossiliferous strata must have a maximum thickness of some one hundred thousand feet. To these should be added the foliated series of beds which clearly underlie the primordial formations, and are probably about thirty thousand feet in thickness. Thus the rocks that are open to the eye of man, to say nothing of those that may be reasoned about from observations made on these superficial masses, are, no doubt, from twenty to twenty-five miles in thickness

an estimate suited to remind the student that there is still room for original research. While an under-estimate may be in some respects better than its opposite, it still involves an injustice to the science; the exact truth being what is wanted, and what simple justice demands.

As an instance of a presentation of facts which is explicit, and in one sense correct, while it yet gives a very exaggerated impression as a whole, take what is said, in several editions of the "Elements," of the agency of icebergs. Particular cases, most of which are comparatively exceptional, are given with such a degree of explicitness, while so little is presented in a favorable light in regard to certain other instrumentalities, that false inferences and implications are almost unavoidably forced upon the mind of the studentimplications and inferences calculated to impart a very distorted view of the actual state of things at given times in the earth's history. This being a kind of special pleading in which Sir Charles occasionally indulges, and by means of which some of his writings are likely to suggest a very onesided aspect of nature, they are certainly not the best suited to go into the hands of beginners. For them a narration of facts should be at once explicit and accurate, and thus evenly balanced-explicit, it being duly spread out that they may get a distinct impression; accurate, there being an exhibition of the subject as it is, without defect or exaggeration, that their apprehension of it may be true.

To proceed: I would now briefly refer to Sir Charles's exposition of progress. A word touching what he says of the older fossiliferous rocks must suffice in that direction. The Obolus sandstone of Russia, sometimes known as the Ungulite grit of Pander, which, indeed, with all the sedimentary beds around St. Petersburg lying beneath the Orthoceratite limestone, should be provisionally recognized as Primordial, the author places, seemingly without a question, in the Lower Silurian. But when he treats of the older Palaeozoic rocks of England, which are rapidly gaining prominence in public estimation, he arranges the Tremadoc slates as Cambrian, though as a series of transition beds they appear to be as closely allied to the Silurian as to the Primordial.

[ocr errors]
[ocr errors]

While Sir Charles's exposition of what is known of these older rocks suggests many points of stricture, I must pass them all by, in order to notice his treatment of some of the more recent strata with which he is more especially at home. In arranging the Tertiary and the Post-Tertiary beds, he formerly placed the Drift and the immediately overlying stratified deposits, in the Tertiary, calling them "Newer Pliocene," or "Plistocene." Other strata, of more recent date, he termed "Post-Pliocene," and arranged them as a part of the Post-Tertiary, just above the Plistocene; the deposits known as Recent succeeding them. With the advance of knowledge it has become evident that the Drift, or Plistocene, is also strictly Post-Tertiary, and thus in a marked manner separated from the Older Pliocene. Now, to sunder the Newer Pliocene (or Plistocene) from the Older Pliocene, calling it Post-Tertiary, to be followed by the Post-Pliocene and Recent, would be very awkward, not to say, strangely unfit. Something, therefore, is to be done; the advance of science cannot be safely overlooked; but then the old percentage theory must be kept up. With a view to these ends, and as a sort of compromise, the author arranges the greater part of the Drift proper, with the overlying stratified beds, in what he now calls the Post-Pliocene. Reserving the remainder of the typical Drift, with its superimposed strata,

which in given localities seem to have a little greater percentage of extinct forms, he places it, with a few other beds, in what he designates in the "Student's Elements" as Newer Pliocene, silently dropping the "Plistocene" altogether. But this is not all. Having appropriated the term Post-Pliocene for the most part to the Drift and its associate stratified beds, he seems largely to ignore the time which really intervened between what he formerly called the Plistocene and the Recent. And this interval, which, in consonance with Sir Charles's terminology, I have sometimes called the Holocene, is not a mere cipher. It properly consists of two parts, viz. the Marl Period and the Peat Period, each of which sober geologists have estimated as at least twenty-five thousand years in length.

Now, whether such an exposition of progress be ingenuous, or whether a proceeding of this kind be trustworthy in its results, I leave others to judge. It is certainly fashionable in some quarters. The student, meanwhile, needs in a textbook, not the whims of a man, or the fashions of the day, but that on which he may rely.

A few words may be next devoted to Sir Charles's recognition of investigators. Speaking of the studies of Cuvier and Brongniart on the Tertiary beds in the neighborhood of Paris, which were published in 1810 the author says (p. 117), "Strata were soon afterwards [afterward] brought to light in the vicinity of London, and in Hampshire, which were justly inferred by Mr. T. Webster to be of the same age as those of Paris, because" of the marked similarity of the fossil shells. While this statement is in one aspect true, it is none the less unjust to previous laborers. Brander long before "brought to light" fossils of the Lower Tertiary "in Hampshire," which he deposited in the British Museum. Of these, in 1766, he published descriptions made by Solander, in a volume illustrated with excellent figures, and for the most part comparing favorably with work done to-day. As is clear from his preface, two remarkable results were reached, viz. (1) that most of the fossils differ from existing species,

and (2) that the representatives of the few forms which closely resemble species now living are only found in warmer latitudes. Thus Brander, while he by no means fully anticipated the grand generalizations of Cuvier, yet evinced extraordinary insight, and did much to prepare the way in England for the recognition of the light shortly to dawn. On these accounts, therefore, he was eminently deserving of credit, in some respects more so than any other man who has had to do with the English Tertiaries; and yet he receives in the "Student's Elements" no mention. Such failure to do justice to an Englishman not widely recognized would not be surprising in a foreigner; but in Sir Charles, who certainly knows Brander, or at least of him, and is supposed to be oracular in regard to the English Tertiaries, it is strangely surprising.

A second instance, out of many that might be cited, must suffice for the illustration of the point under consideration. If students simply read what is said of glacier agency in the eleventh chapter of this volume, and especially the reference (p. 145), "I have described elsewhere" (Principles, etc.), taken in connection with the fact that express mention is made of only Vinetz and Charpentier as early observers of the Swiss glaciers, they can hardly fail to get the impression that Sir Charles was foremost in noticing the evidences of glaciation, and that the main credit of the glacier-theory is due to him. Again, if they merely read what he says of the glaciation of Scotland, they will naturally infer that Professor Jamieson was the first to find evidence of the former existence of glaciers in that region. Now, the fact is that Professor Agassiz, having followed up the inquiries of the few earlier workers by critical investigations of his own on the glaciers of Switzerland, was the first to make the grand generalization that drift phenomena generally are due to the agency of continental ice-masses; that, in 1840, he was the first to extend this generalization to the British Isles; and that, during the same year, he designated the period of drift as the Ice or Glacial period. It is also a fact that Sir Charles,

[ocr errors]
« PreviousContinue »