Relics of Primeval Life: Beginning of Life in the Dawn of Geological Time

by Sir John William Dawson

Logan was, however, a man not to be daunted by an unsolved problem, even though the facts for its solution must be sought in a wilderness known to few except adventurous trappers, hunters, and lumbermen; and he soon learned that this ancient gneissic formation contained other rocks beside gneiss, more especially thick and extensive limestones, and that its beds seemed to have a definite arrangement, and could be traced over great areas. He addressed himself, therefore, to the problem of unravelling the tangled "complex," and with a few hardy assistants, spent years in laboriously tracing its beds along river courses and over mountains, and in mapping, in a manner never previously attempted, its several members, designating at the same time the whole by the term "Laurentian," because it constituted the mass of the hills lying north of the St. Lawrence, called by old French geographers the Laurentides, and separating the St. Lawrence Valley and the region of the great lakes from Hudson's Bay and the Arctic Sea. In this manner he laid a foundation, which still remains unshaken, for the geology of the oldest rocks, and prepared the way for the discovery of the forms afterward named Eozoon Canadense. At the same time Dr. Sterry Hunt, the chemist of the Survey, was examining chemically the rocks and minerals collected, and all Sir William's assistants were instructed to search, more especially in the limestones, for anything bearing the aspect of fossils. On the other hand. Dr. Carpenter was independently pursuing his studies of the humbler inhabitants of the modern ocean, and of the manner in which the pores of their skeletons became infiltrated with mineral matter, and had kindly contributed specimens to the collections of the writer in Canada. The discovery of this most ancient fossil was thus not the chance picking up of a rare and curious specimen, but the result of several combined lines of laborious and skilful research.

The following notice of the persons and incidents connected with its discovery is taken from a previous publication of the writer, with only a little alteration in terms to suit it to the present date.

The first specimens of Eozoon ever procured, in so far as known, were collected at Burgess, in Ontario, by a veteran Canadian mineralogist. Dr. Wilson of Perth, and were sent to Sir William Logan as mineral specimens. Their chief interest at that time lay in the fact that certain laminæ of a dark green mineral present in the specimens were found, on analysis by Dr. Hunt, to be composed of a new hydrous silicate, allied to serpentine, and which he named loganite, but which seems to be a mixture of different silicates. The form of this mineral was not suspected to be of organic origin. Some years after, in 1858, other specimens, differently mineralized with the minerals serpentine and pyroxene, were found by Mr. J. McMullen, an explorer in the service of the Geological Survey, in the limestone of the Grand Calumet on the river Ottawa. These seem to have at once struck Sir W. E. Logan as resembling the Silurian fossils known as Stromatoporæ, or layer-corals, and at that time of quite uncertain nature, though supposed to be allied to some kinds of modern corals. He showed them to Mr. Billings, the palæontologist of the Survey, and to the writer, with this suggestion, confirming it with the sagacious consideration that inasmuch as the Ottawa and Burgess specimens were mineralized by different substances, yet were alike in form, there was little probability that they were merely mineral or concretionary. Mr. Billings was naturally unwilling to risk his reputation in affirming the organic nature of such specimens; and my own suggestion was that they should be sliced, and examined microscopically; and that if fossils, as they presented merely concentric laminæ and no cells, they would probably prove to be protozoa rather than corals. A few slices were accordingly made, but no definite structure could be detected. Nevertheless, Sir William Logan took some of the specimens to the meeting of the American Association at Springfield, in 1859, and exhibited them as possibly Laurentian fossils; but the announcement was evidently received with some incredulity. In 1862 they were exhibited by Sir William to some geological friends in London, but he remarks that "few seemed disposed to believe in their organic character, with the exception of my friend Professor Ramsay." In 1863 the General Report of the Geological Survey, summing up its work to that time, was published, under the name of the "Geology of Canada," and in this, at page 49, will be found two figures of one of the Calumet specimens, here reproduced, and which, though unaccompanied with any specific name or technical description, were referred to as probably Laurentian fossils (Figs. [26] and [27]).

Fig. 26.—Weathered Specimen of Eozoon from the Grand Calumet. (Collected by Mr. McMullen.)

Fig. 27.—Cross Section of the Specimen represented in [Fig. 26].
The dark parts are the laminæ of calcareous matter converging to the outer surface.

About this time Dr. Hunt happened to mention to me, in connection with a paper on the mineralization of fossils which he was preparing, that he proposed to notice the mode of preservation of certain fossil woods and other things with which I was familiar, and that he would show me the paper in proof, in order that he might have any suggestions that occurred to me. On reading it, I observed, among other things, that he alluded to the supposed Laurentian fossils, under the impression that the organic part was represented by the serpentine or loganite, and that the calcareous matter was the filling of the chambers. I took exception to this, stating that though in the slices before examined no structure was apparent, still my impression was that the calcareous matter was the fossil, and the serpentine or loganite the filling. He said: "In that case, would it not be well to re-examine the specimens, and to try to discover which view is correct?" He mentioned at the same time that Sir William had recently shown him some new and beautiful specimens collected by Mr. Lowe, one of the explorers on the staff of the Survey, from a third locality, at Grenville, on the Ottawa. It was supposed that these might throw further light on the subject; and accordingly Dr. Hunt suggested to Sir William to have additional slices of these new specimens made by Mr. Weston, of the Survey, whose skill as a preparer of these and other fossils has often done good service to science. A few days thereafter, some slices were sent to me, and were at once put under the microscope. I was delighted to find in one of the first specimens examined, which happened to be cut parallel to the laminæ, a beautiful group of tubuli penetrating one of the calcite layers. Here was evidence, not only that the calcite layers represented the true skeleton of the fossil, but also of its affinities with the Foraminifera, whose tubulated supplemental skeleton, as described and figured by Dr. Carpenter, and represented in specimens in my collection presented by him, was evidently of the same type with that preserved in the canals of these ancient fossils. [Fig. 28] is an accurate representation of the first seen group of canals penetrated by serpentine.

On showing the structures discovered to Sir William Logan, he entered into the matter with enthusiasm, and had a great number of slices and afterwards of decalcified specimens prepared, which were placed in my hands for examination.