ORDINARY MEETING.* D. HOWARD, Esq., V.P., IN THE CHAIR. A paper entitled "Geological Exterminations," by Charles B. Warring, M.A., Ph.D., was read by the Secretary, in the author's absence in Canada. The Secretary also read communications from Mr. Hudleston and Dr. Kidd. A GEOLOGICAL EXTERMINATIONS. By CHARLES B. WARRING, M.A., Ph.D. LL who have studied the life-history of the earth have been impressed with the fact that not only species, but entire genera, families and tribes, have become extinct-not temporarily but permanently, and, broadly speaking, have been succeeded by species more like those of the present day. Dana says: "There was a general extermination of species about the eastern portion of the American continent at the close of the Acadian or Lower Silurian epoch; at the end of the period of the Chazy formation its species, with few exceptions, disappeared." He says also: "The introduction and extermination of species were going on during the whole course of history, instead of being confined to particular points of time; but at the close of long periods and epochs there were general exterminations." He says also: "At the close of the Cretaceous period occurred one of the most complete exterminations of Monday, March 6th, 1905. + Dana, Mun. of Geol., Revised edition, page 182, lines 13 to 20. Ibid., page 384, lines 21 to 24. + species of which we have any record."* quotations, but there is no need. I might multiply such A very important fact in this connection is that after these exterminations the old species do not reappear, but new ones, more like those of to-day, take their places. The biological conditions, therefore, must have changed in the interval, probably a long one, between the birth and death of those species, and always in the direction of those that now prevail; and as this change of species took place all over the world, an explanation must be sought in a cause, or causes, possessing the same characteristics of permanency and universality. It is usual to attribute these exterminations to the occurrence of continental elevations producing colder climate, or to high latitude depression of land letting cold waters from circumpolar regions flow towards the equator. It is doubtful whether these were sufficiently extensive to be world-wide, and, however that may be, they lack permanency; for in a short time, geologically speaking, the elevations were followed by depressions, and the parts that had been sunk below the normal level came up again; and as for cold water currents, if we may judge from the flora and fauna which have been preserved, circumpolar waters during by far the greatest part of the time when the exterminations occurred differed in temperature but little, if at all, from those within (or at least near) the tropics. It is found that from the Eozoic to the close of the Mesozoic, and in a less degree through the Miocene, one of the most striking characteristics of each horizon was the world-wide prevalence of very similar, and often identical species, with little or no regard to differences of latitude. It was during that time of mild and uniform climate that the most numerous and most remarkable exterminations took place. There may have been local elevations sufficient to produce even large glaciers-mountains in tropical regions have such now-but their influence in the early days was too limited to need to be considered in this connection. We inust, therefore, look elsewhere for causes which were both worldwide and permanent, and which rendered a return to former biological conditions impossible. These we shall find, if I mistake not, in the continuous improvement from the dawn of life in the character of the atmosphere, the waters, and the soil. Its influence was world-wide, never going back, perma * Man. of Geol., page 487, near bottom. nent, and always working towards present conditions, and, therefore, rendering a return of former species impossible. But the question arises, was there such improvement? The early atmosphere must have contained an enormous amount of carbonic acid, or, as it is now called, carbon-dioxide, for though at one time carbon and oxygen were kept disassociated by the intense heat, yet as the temperature fell, a point was reached when their usual affinities brought them together till one was exhausted. Probably some free oxygen was left, because after that-I know not how soon-there were found protozoa, and these, like all other animals in the water and on the land, require such oxygen. A very large part of the carbon dioxide had united with lime and other bases, forming insoluble deposits, before the Eozoic. The atmosphere was improved by the operation, but became no richer in oxygen; for this vegetation was necessary. When there began to be even the lowest plants, the oxygen of the dioxide commenced to be freed from the carbon, and returned to the atmosphere, while the other element, the carbon, gave suitable material to plants and their dependents, the animals. All those then living, and all that have come after them, whether now living or buried in the earth as graphite, coal, lignite, oil, gas, or in other forms, existed at the opening of the Eozoic period as carbon-dioxide. Hence its atmosphere was poorer in free oxygen by the amount necessary to turn all that carbonaceous matter back to dioxide, and this, the chemists tell us, is eight pounds of oxygen to only three of carbon; or, to put it in another way, one pound of carbon will turn into dioxide two and a half pounds of oxygen, or, more exactly, two and two-third pounds. It is impossible to determine the amount of carbon which has passed through plants and animals, but from what has already been found in the comparatively small part of the earth's crust which has been examined, and from what we may reasonably suppose has been carried into the sea, it was sufficient to hold a very large part, probably by far the largest part of the present free oxygen, as carbon-dioxide. In every hundred pounds of the present atmosphere there are about twenty-three pounds of free oxygen. At the beginning of the Eozoic period, when all subsequent organisms existed only as carbon-dioxide, the amount of free oxygen in one hundred pounds of the atmosphere was very small, perhaps not more than one or two pounds. The atmospheric improvement since has been enormous. The carbon-dioxide is now M only a trace, scarcely 4 parts out of 10,000, while the oxygen has increased to 2,300 out of the same amount. The ratio has so changed from being only a fraction compared with the CO2, that the oxygen to-day is almost 600 times the greater. At no time is there evidence of a return to conditions once passed. The tendency of gases is to diffuse themselves uniformly, irrespective of their specific gravities. This process was aided by aerial currents. There resulted from such action uniformity of atmospheric composition over both land and sea, and in all latitudes. To-day we see the same thing from the same causes. During the same geological time changes were going on in the water, changes whose biologic influence manifested themselves, or at least were accompanied by, changes of species in the direction of those which now exist. The enormous deposits of what, for lack of a better name, I may call organic limestone and silicates, indicate waters once holding in solution proportionally large amounts of lime and silica. These amounts were greatest at first, and grew less and less as plants and animals progressed in the work of making those insoluble compounds in which so much has been stored away. The amount of lime and silica held by the water was therefore greatest in the Azoic time, grew less in the Eozoic, less yet in the Silurian, less still in the Devonian, and so on down, each period having less than the one before it; until at last, probably in the Quaternary, an equilibrium was reached by the inwash from the land making good that which is removed by present animal and vegetable action. The presence of these deposits in all latitudes indicates the world-wide character of this process. Moreover the ocean currents, tides and winds, tended to uniformity in the character of the water everywhere. To-day, from local causes, some parts of the ocean hold a larger percentage of mineral matter than do some others, yet on the whole the great ocean is everywhere substantially the same, and probably such was the case in each of the geological periods. The third biological factor is the soil. This affects directly only vegetation, but indirectly all other forms of life. As soil is a compound of comminuted rock and vegetable and animal matter, we may safely assume that, while before the Eozoic the former was present as clay, sand, and gravel, there was no soil. This began to form after the other ingredients had been washed upon the emerged land; it increased in quantity and improved in quality as time went on through the ages. If we may judge from the flora, it reached its present quality in the Pliocene. The change since that period appears to have been an increase of its amount. It seems, therefore, from the rock-record, that the free oxygen in the atmosphere, the purity of the water of the seas, and the quality of the soil went on, side by side, ever increasing from the dawn of life, till at last the loss and gain became equal near this end of the world's history. In short, there was from period to period a great improvement, world-wide and permanent, in the life-sustaining powers of these biological factors, and always towards present conditions. Those at the first were prohibitive of any form of life; we know what they are now. Intermediate in time the conditions made only intermediate progress, and the rocks show organisms intermediate between the earliest and latest forms. Was this coincidence merely a matter of chance, or was it an instance of cause and effect? It appears to me to be the latter, because an intimate relation exists between species and their environment. Leaving out of account temperature, which seems during by far the larger part of geological time to have been pretty much the same everywhere, what other environments existed besides those which we are now considering? Is it not reasonable to suppose that changes in them would seriously affect both plants and animals? That floras and faunas disappeared admits of no doubt, and, so far as I am aware, no other causes possessing the world-wide extent and permanency required are known. Nor are we confined to theoretical reasoning. Not a few facts are established which have an important bearing on the question. Birds and small mammals, placed in an atmosphere having two or three times the normal amount of oxygen, do not long survive. Fishes brought out of water are said to die from the great amount of oxygen they are compelled to inhale. Plants too highly manured lose the power of reproduction. The seed does not form, or if it forms, does not mature. Even corals are sensitive to the purity of the water in which they live, and if that is materially changed they die. If this is true of present species, is it unreasonable to believe that organisms made for the atmosphere, water and soil of their native period, would die out when these had greatly changed? In this progressive improvement in the quality of these biological factors is found, it seems to me, at least one cause-perhaps the cause -of the disappearance of species and of their never reappearing. Organisms to-day have the power of adapting themselves to |