Carrying these facts with us, the next question is, What manner of fossil remains should we expect to find in the Upper Laurentian rocks, supposing that any such are therein preserved? The answer to this question follows at once from the facts as to the succession of life noticed above. Only the marine invertebrates have been traced as far back as the oldest Cambrian, and only Worms, Sponges, and Protozoa into the Huronian. We should therefore have no expectation of finding remains of any vertebrate animals or of any of the land invertebrates; and even allowing for the more favourable conditions, as compared with the Huronian, evidenced by the great limestones and the abundant carbon, we could scarcely expect anything higher than some of the lower types of invertebrate life, such as Worms, Hydroids, Corals and Protozoa. We have next to inquire what forms, possibly organic, have actually been found, and what information we can derive from them as to the beginnings of life. Since, however, such discoveries as have been made have been the result of much labour and scientific skill brought to bear on these old rocks, and are connected with the reputations of several eminent men, now deceased, we may first refer shortly to the history of the discovery of supposed fossils in the Laurentian rocks of Canada. [Illustration: Fig. 25.--_Nature-print of an etched Specimen of Eozoon._ Showing the laminæ, a part of the natural margin, near which passes a diagonal calcite vein, and at the upper right-hand corner, fragmental material with casts of Archæospherinæ. The dark lines represent the chambers filled with serpentine, the white the calcite wall.] _THE HISTORY OF A DISCOVERY_ VI _THE HISTORY OF A DISCOVERY_ When Mr. Logan, afterwards Sir William Logan, entered on the Geological Survey of Canada, in 1840, he found that vast and little-explored regions in the northern part of that country were occupied with gneissic rocks, similar to the oldest gneisses of Scotland and Scandinavia, and to which the name Azoic had been given by Murchison, as rocks destitute of fossils, while they had been the "fundamental granite" or ur-gneiss of most European geologists. They were unquestionably below and more ancient than the oldest fossiliferous Cambrian rocks both in Europe and North America, and geologists had for the most part contented themselves with regarding them as primitive rocks, destitute of any geological interest, much as some United States geologists of the present day call them the "Archæan complex," a name which the late Prof Dana has well characterized as a "term of despair."