during wet summers.

In such seasons the moles would burrow in lands which had

been too dry for them when the opposite conditions prevailed.

It is difficult to estimate when this process began, but it must have been long ago, and over much of the country it is carried on every autumn, although in some parts, as we have seen, it is only resumed at intervals of a few years. Were it not for this constant renewal of the supply by the covering over of the vegetation through the repeated digging of the moles, etc., the organic matter, which is being constantly oxidized and destroyed, would in time disappear entirely out of the soil, and the whole country become comparatively barren.

Moles are scarce or absent on the elevated, hard and stony portions of the third steppe, such as the Grand Coteau du Missouri, and much of the great plain between the north and south branch of the Saskatchewan, and also on the stiff clays of the south branch and the upper Qu'Appelle. They are most abundant in what is called the prairiecountry (as distinguished from the naked plains), such as the great belt between the wooded region of the north-east and the open plains to the south-west, and again along a belt east of the Rocky Mountains, and parallel to their course. These are the regions which embrace the most fertile lands of the second and third steppes.

The labour of the moles in thus improving the land is supplemented by that of the gophers, spermophiles or ground-squirrels, and in some sections by that of the badgers. The last-named animals do a rough kind of work. They dig deeply into the ground, and in gravelly or stoney tracts throw up large quantities of the coarse subsoil over the top of the vegetable mould, apparently doing more harm than good in such cases, unless we consider their work as a sort of sub-soil ploughing, or first step in the process of deepening the soil-stratum. For, in the course of time, the moles will bury the stones thrown out by the badgers, and mingle the finer material of these heaps of subsoil with the vegetable mould which they originally covered. Except in wet places, or where the ground is too hard and dry, the prairies are riddled with great numbers of badger-holes, which seriously interfere with riding or driving across them. Even the well-travelled trails are at intervals so undermined and honey-combed with fresh badger-burrows that it becomes necessary to turn aside and go around them. Where the subsoil is fine, as in the yellowish sandy and clayey loam, which prevails in some parts, the burrowing of the badgers is directly beneficial in increasing the depth of the soil, without the intervention of the moles. This is the case, for instance, in Prince Albert settlement, where, although the badgers are now exterminated, their earth-heaps are everywhere visible, even in the streets of the town.

In the vertical sections of the soil which may be observed in various parts of the territories, the remains of ancient badger-holes may be seen in the abrupt depressions in the line of the subsoil, now filled with black vegetable mould. In connection with the subject of the burying of vegetable matter by the various animals I have referred to, it may be mentioned moreover that quantities of grass and leaves fall into their burrows, and are also carried deeper into them by some of the animals for making their nests, and that when the burrows break down, this vegetable matter decays and contributes to the formation of the soil.

A circumstance that greatly aids the process of enrichment of the land which has

Sec. IV., 1883. 21.

just been described, is the fact that the moles, and all the other animals which have been mentioned, are most active in their labors in the autumn, say, from the early part of September until the hard frost sets in, or during the period when the grass and other prairieplants have matured and contain in their tissues the maximum amount of substance. During the spring and summer they appear to have little inclination to burrow, their attention being occupied with raising their families or other matters, but after the beginning of September they all become very busy, as if they were deeply impressed with the necessity of digging a great many holes in the ground. It is astonishing how many burrows each individual of these different kinds of animals will dig. In most cases it is difficult to perceive what benefit the creature itself can derive from this promiscuous digging of a multitude of burrows. At this busy season the animals themselves are in the best condition, food being easily obtained, and it really seems as if the object of the energy and activity which they then display were mainly for the purpose of turning over, deepening and enriching the soil. Darwin has shown conclusively that the work which may be accomplished by earth-worms, even in a comparatively short period, is enormous, but their labors are slow compared with those of the moles, gophers, spermophiles and badgers.

During the summer months, the surface of the ground in the North-West becomes heated in the day-time, but this season is of comparatively short duration, and the heat does not penetrate deeply, so that even in the warmest season the average temperature of the soil a short distance below the surface is low, as was demonstrated by Captain Palliser's series of observations; while it is frozen solid for about five months of the year. This tends to preserve the organic matter, on which, with sufficient moisture, its fertility mainly depends, since the precise chemical composition and proportions of the commoner inorganic constituents do not seem to be of much consequence in this connection. The soils of the North-West are, however, rich in phosphates and sulphates, in lime and in potash.

Although the region which has been spoken of extends through eleven or twelve degrees of latitude, its climate is pretty uniform throughout. I have described what I consider to be the fundamental and also the immediate or direct causes of the fertility of its soil, but perhaps the remote cause, is to be looked for in its northern situation. It is the sufficiently cool and moist climate (as compared with the arid regions of the south) that produces the rich growth of grasses, the repeated burial of which year after year, as we have seen, enriches the land. It also allows of the existence of the insects, roots, etc., the food of the animals which perform this work, and finally it prevents the rapid decay and disappearance of the fertilizing organic matter after it has become incorporated in the soil. We can thus trace a mutual dependence of those circumstances which together have given to our North-West territory that surpassing fertility of soil, which will attract to it a vast population, notwithstanding its present distance and the severity of its winters.

If the fertility of tens of millions of acres of land in the North-West, and consequently their value, have been mainly due to the work of moles, these apparently insignificant little creatures may be regarded as the most important of the native animals of the country. The condition of the soil of the North-West, resulting from the processes which have been described, is not without its geological interest, since it shews that the prairies must have existed for a great length of time. Various other facts also tend to prove this, and, indeed, it is doubtful if the forests of modern geological times ever extended much beyond their present limits.

IX.-Note sur la Géologie du lac St-Jean.

Par M. l'Abbé J. C. K. LAFLAMME, D.D.

(Lu le 25 mai, 1883.)

Dans son rapport sur la Géologie du Canada publié en 1863, Sir William Logan notait la présence au lac St-Jean de plusieurs groupes de terrains appartenant au Silurien inférieur. Après avoir cité l'observation faite par Major Baddeley, en 1828, Sir William ajoutait que ces terrains devaient couvrir à peu près tout le fond du lac. Cependant, les seuls endroits où on les signale sont, d'abord une île basse située à environ un mille au large de la Petite Décharge, puis la rive sud du lac, depuis le poste de la Compagnie de la Baie d'Hudson jusqu'à la Pointe-Bleue. Ces terrains appartiennent aux calcaires de Trenton ou Black River et au groupe Utica et Rivière Hudson. Je me permettrai d'ajouter à ces renseignements quelques observations faites durant l'été de 1882.

Les calcaires de Trenton se trouvent encore très-développés sur la rive gauche du Saguenay, depuis Ste-Anne jusqu'à quelques lieues en deçà du confluent des deux décharges. Les lits sont éminemment fossilifères, et parmi ces fossiles, on reconnait facilement ceux qui caractérisent l'horizon géologique du Trenton. Ils sont exploités comme pierre à chaux et comme pierre à bâtir.

J'ai encore découvert les mêmes lits au sud-est de l'embouchure de la Métabetchouan. Leur position curieuse mérite d'être décrite.

Ils sont à peu près horizontaux et reposent immédiatement sur les gneiss laurentiens. Leur épaisseur à cet endroit ne dépasse pas une cinquantaine de pieds. Il va sans dire qu'autrefois cette épaisseur devait être beaucoup plus grande, mais les glaciers quaternaires en ont fait disparaître une quantité considérable.

Au nord de ce petit îlot Silurien se trouve une colline Laurentienne sur les flancs de laquelle viennent successivement s'appuyer les lits calcaires. Evidemment, c'est à la présence de cet éperon gneissique que les couches Siluriennes doivent d'avoir été préservées en grande partie de l'action érosive des glaciers. D'autant plus que le côté nord de la colline est fortement arrondie, une vraie "roche moutonnée," tandis que le côté sud-est est beaucoup plus abrupte.

Nous aurions donc là un reste des aspérités qui se trouvaient sur le fond de la mer Silurienne, une espèce de bas-fonds ou d'écueil.

Ces calcaires sont extrêmement riches en pétrole. En cela ils suivent la règle générale pour tous les calcaires de Trenton. Durant le cours de l'été 1882, un cultivateur qui exploitait ces assises comme pierre à chaux, a retiré plusieurs gallons de pétrole brut rien qu'en cassant la pierre pour la jeter au four.

Inutile de dire qu'ils abondent en fossiles. Cependant, ceux-ci, à peine visibles dans une cassure fraîche, sont fort difficiles à déterminer. Dans les surfaces exposées à l'atmosphère on voit que plusieurs lits ne sont en réalité que des masses de fossiles, entiers ou en fragments.

Comme conséquence générale, je crois qu'on devrait modifier notre carte géologique, telle que publiée par Sir W. Logan, en ce qui regarde le lac St-Jean. Il faudrait étendre les formations Siluriennes au nord du Saguenay jusque près de Chicoutimi, et en signaler de plus quelques dépôts isolés, depuis le lac Kénogamischiche jusqu'à la Pointe-Bleue.

Je regrette que le temps ne m'ait pas permis de définir complètement les contours de ces dépôts Siluriens. Toutefois il est probable qu'ils forment une large bande distribuée à peu près parallèlement à la rive gauche du Saguenay.

De là on peut conclure que la mer Silurienne devait avoir, dans ces parages, une grandeur à peu près équivalente à celle de la mer quaternaire; que la dépression du lac St-Jean a existé dès le commencement de l'histoire géologique; que les divers mouvements qui ont pu s'y produire n'ont pas affecté profondément le système des reliefs de

cette contrée.

Je viens de parler des soulèvements et affaissements locaux. A ce propos, qu'il me soit permis de signaler un fait qui a quelques rapports avec eux.

Il parait assez probable que le soulèvement qui s'est produit à la fin de l'époque Champlain a été, au lac St-Jean, bien plus marqué vers le milieu de la rive sud qu'aux deux extrémités orientales et occidentales du lac. Les terrasses y sont beaucoup plus élevées. En effet, à St-Prime et à la Décharge, elles sont presque au niveau des hautes eaux, tandisqu'à Hébertville, elles le dépassent de 150 pieds.

On ne peut pas dire que cette différence de niveau soit due à plusieurs systèmes de terrasses se succédant les unes aux autres, puisque, dans plusieurs localités, il est facile de voir la surface générale des dépôts quaternaires sensiblement arrondie et s'inclinant du côté de la Décharge et de St-Prime.

Ceci étant admis, ne peut-on pas conclure que tout le bassin hydrographique du lac se déchargeait autrefois par les lacs Kénogamischiche et Kénogami dans la baie des Ha! Ha! Il y a là un chenal tout tracé, et qui, même actuellement, est presque aussi profond que le Saguenay lui-même, bien que le lac Kénogami soit à plus de 300 pieds au-dessus du fleuve.

Ce débouché aurait persisté jusqu'à l'époque glaciaire, où il aurait été complètement obstrué par les débris sableux et argileux charroyés par le glacier.

Ce fut alors que la Décharge actuelle commença à jouer son rôle. On s'explique ainsi comment la partie du Saguenay placée au-dessus de Chicoutimi est beaucoup moins profonde que le reste de la rivière: elle est moins ancienne.

X.-The Geological History of Serpentines, including Notes on pre-Cambrian Rocks.

By THOMAS STERRY HUNT, M.A., LL.D. (Cantab.), F.R.S.

(Presented May 23, 1883.)

I.-Historical Introduction.-Discordant opinions as to the geognosy of serpentine; views of various European geologists; of American geologists; geological survey of Canada. Origin of crystalline rocks; plutonism; metasomatic hypothesis; neptunism; aqueous origin of magnesian silicates. A fundamental question in geogeny.

II.—Serpentines in North America.-Laurentian and Huronian serpentines; those with the younger gneisses and mica-schists. Serpentines of Chester Co., Pennsylvania; of Staten Island, Hoboken, Manhattan and New Rochelle; Taconian serpentines in Pennsylvania. Silurian serpentine of Syracuse, New York; its history. Sepiolite and other hydrous magnesian silicates.

III.-Serpentines in Europe.-The hypothesis of their igneous origin. Nomenclature of serpentines and related rocks. Views of some Italian geologists. Serpentines at the geological congress of Bologna.

IV.-Rocks of the Alps and the Apennines.—Early views. Studies of Gastaldi, von Hauer and others. Ancient gneiss; pietre verdi or greenstones; newer gneiss; youngest crystalline schists. Four pre-Cambrian groups in the Alps defined. Rocks of the Apennines and the adjacent islands.

V.-Italian Serpentines.—Their classification; plutonic and hydroplutonic theories of their origin. Serpentines of Tuscany, Liguria and the Alps. Antiquity of the so-called tertiary serpentines.

VI.-The Genesis of Serpentines.-Theories of plutonic and neptunian metasomatism; diagenesis. The derivation of serpentine from olivine, and the hydroplutonic hypothesis considered in relation to vulcanism. Theory of original deposition. History of olivine rocks.

VII.-Stratigraphical Relations of Serpentines.-Their supposed intrusive character considered. Stapff on the serpentines of the St. Gothard.

VIII.-Conclusions; followed by an analysis of the Contents of Sections and Note.

I-HISTORICAL INTRODUCTION.

§ 1. Few questions in geology are involved in greater obscurity or more contradiction, than the history of serpentine-rocks. As a preliminary to a discussion of certain observations by myself and others thereon, it seems, therefore, desirable to recall some passages in this history which may serve to show the differences of opinion now existing and, it is hoped, prepare the way for their reconciliation. These differences may be considered under two heads: namely, the geognosy of serpentine, or its relation to the other rocks of the earth's crust, and the geogeny, or the origin and mode of formation of serpentine.

Setting aside for the moment the question of the occurrence of serpentine as an accidental mineral disseminated in calcareous rocks, and considering only its occurrence in rock-masses, either pure or mingled with other silicates, the first question which presents itself is whether such massive serpentines are contemporaneous with the enclosing rocks, or whether they have been subsequently intruded among these:-in other words, whether serpentines are indigenous or exotic rocks.