It may also be found that the beds of limestone are fewer and their repetitions more numerous than had been supposed, and that the Grenville series may be closely associated locally, at least, with beds hitherto of uncertain age, or associated with the Lower Huronian. The Huronian proper, on the other hand, may be considerably extended, and the Kewenian and Animiké series overlying it have already been ascertained by the Canadian Geological Survey to overlap the Huronian and Laurentian over vast areas between the great lakes and the Arctic sea, evidencing much submergence at the close of the Huronian age, and opening of the Palæozoic. I have noticed in the text the apparently wide development of deposits of this age over the area of the Rocky Mountains of Canada, and the corresponding territories in the United States. There would seem to be in these regions a great thickness of unaltered sediments between the Lower Cambrian and the crystalline rocks below, representing the Huronian and Laurentian. In these very few fossils have yet been found, but they afford perhaps the most promising field, next to their representatives in Newfoundland and New Brunswick, for the discovery of the predecessors of the Olenellus fauna, and the forms of life connecting these with those known in the Huronian and Laurentian. [For summaries of facts on the last-mentioned subject, see Report of Dr. G. M. Dawson on the Kamloops map-sheet, in "Reports of Geological Survey of Canada," vol. vii. B, new series, pp. 29 et seq.; also Reports of Dr. C. D. Walcott, U. S. Geological Survey, vol. xiv., Part I., pp. 103 et seq., and Part II., pp. 503 et seq.]

B. Preservation of Organic Remains by Injection with Hydrous Silicates.

The late Dr. T. Sterry Hunt contributed to the original paper on Eozoon in the Journal of the Geological Society, a valuable essay on the mineralization of fossils by serpentine, glauconite, and allied hydrous silicates. This was in part reprinted in the notes appended to one of the chapters of "The Dawn of Life," and the subject was further discussed by Hunt in his invaluable work, "Chemical and Geological Essays," and more especially in the chapter on the "Origin of Crystalline Rocks," a chapter which every geologist deserving the name should study with care.

I give here some of the more important facts referred to by Hunt, and may add that subsequent microscopic studies have familiarized me with the occurrence of serpentine and other hydrous silicates as fillings of the cavities of fossils of various geological ages, insomuch that I have come to regard the occurrence of these rocks in association with fossiliferous limestones as among the best available means to enable us to ascertain the minute structures of shells, Foraminifera, corals, etc.

The following remarks and analyses further illustrate Hunt's views on the relations of these minerals, with some of the facts on which they are based:—

"In connection with the Eozoon it is interesting to examine more carefully into the nature of the matters which have been called glauconite or green-sand. These names have been given to substances of unlike composition, which, however, occur under similar conditions, and appear to be chemical deposits from water, filling cavities in minute fossils, or forming grains in sedimentary rocks of various ages. Although greenish in colour, and soft and earthy in texture, it will be seen that the various glauconites differ widely in composition. The variety best known, and commonly regarded as the type of the glauconites, is that found in the green-sand of Cretaceous age in New Jersey, and in the Tertiary of Alabama; the glauconite from the Lower Silurian rocks of the Upper Mississippi is identical with it in composition. Analysis shows these glauconites to be essentially hydrous silicates of protoxyd of iron, with more or less alumina, and small but variable quantities of magnesia, besides a notable amount of potash. This alkali is, however, sometimes wanting, as appears from the analysis of a green-sand from Kent, in England, by that careful chemist, the late Dr. Edward Turner, and in another examined by Berthier, from the calcaire grassier, near Paris, which is essentially a serpentine in composition, being a hydrous silicate of magnesia and protoxyd of iron. A comparison of these last two will show that the loganite, which fills the ancient Foraminifer of Burgess, is a silicate nearly related in composition.

I.Green-sand from the calcaire grossier, near Paris. Berthier (cited by Beudant, "Mineralogie," ii., 178).
II.Green-sand from Kent, England. Dr. Edward Turner (cited by Rogers, Final Report, Geol. N. Jersey, page 206).
III.Loganite from the Eozoon of Burgess.
IV.Green-sand, Lower Silurian; Red Bird, Minnesota.
V.Green-sand, Cretaceous, New Jersey.
VI.Green-sand, Lower Silurian, Orleans Island.

The last four analyses are by myself."

I.II.III.IV.V.VI.
Silica40·048·535·1446·5850·7050·7
Protoxyd of iron24·722·08·6020·6122·508·6
Magnesia16·63·831·471·272·163·7
Lime3·32·491·11
Alumina1·717·010·1511·458·0319·8
Potashtraces6·965·808·2
Soda·98·75·5
Water12·67·014·649·668·958·5
—————————-—————-
98·998·3100·00100·00100·00100·0