In lieu of an abstract, here is a brief excerpt of the content:

DINOSAURS IN THE ROYAL ONTARIO MUSEUM W. A. PARKS I T HE beauty of lake and forest, the majesty of mountains, the serenity ofpalm-bedecked tropical islands are alike due to differences in the geological structure of the respective regions. This fact is apparent to all observers, but many fail to appreciate the changes that are constantly occurring-the filling of the lakes with sediment, the wearing-away of the mountains, or the , encroachment of the seas on the tropical strands.. The scenes of to-day are evanescent but the elements of those scenes were born in the past, and at definite, ascertainable times in the past. In viewing a landscape, therefore, 'a geologist pays due regard to the component structures but he further regards those structures ~s concrete evidence ofpast events. - His time sense is ever to the fore; he is an historian and his documents are the rocks of the earth's crust. The earth is very old, how old we do not know, but two billion years ago it was old enough to have a rocky surface and cool enough to permit water to remain on the surface. Land and water had appeared and geological history in the narrower sense had begun. Ever since this early beginning the lands have been the prey of the elements and the waters h~ve been the depositories of the debris produced by the decay of the lands. So long is geological time that but a small fraction of it would suffice to carryall land into the sea and to render the world a watery waste were it not for the fact that the earth's crust is not stahle but is capable of moving up or , down. Downward movements permit the seas to spread 179 THE UNIVERSITY OF TORONTO QUARTERLY over the continents and receive the debris from the remaining land. Upward movements raise the old seabottoms out of water and rejuvenate the continehts. We have, therefore, two opposing factors: ,(a) destruction of land and accumulation in the water (assisted by downward movements); (b) rejuvenation of the lands by' .upward movements. Herein lies our, basis for tracing the history of the earth and for dividing it into chapters and lesser divisions. Theoretically we may assum.e a long period during which the continents are subject to wear and tear and to invasions by the seas with the consequent production of new rocks, followed by a period of elevadon whereby the continents are restored. Such a series of events co~stitutes a cycle of time. Unfortunately for simplicity, only the greatest of these cycles are worldwide ; minor cycles are more local, rendering the interpretation of the rock-written history exceedingly complex. Nevertheless, these principles are the basis on which the history of the earth is divided into chapters, in so far as the physical evidence is concerned. Water-made rocks of different ages are in many cases so alike, and rocks of the salne age in different places so different that it would be almost impossible, on physical evidence alone, to work out the true sequence of strata for the whole world ยท or to compare the rocks of one con~inent with those of another. We have, however, in the organic evidence a most valuable aid to interpreting the physical evidence. The remains ofplants and animals entombed in the rocks, the fossils, can be used in determining the age of a given layer of rock, and are indispensable where physical evidence fails. These relics of the past form one great orderly sequence, differing only in detail in different parts of the world. Constantly changing, but always in the same direction, and never repeating, they 180 DINOSAURS IN THE ROYAL ONTARIO ' MUSEUM constitute t~e most reliable means of correlating strata and establishing the history of the earth. Furthermore, they are themselves the evidence for interpreting the "organic history of the earth which marches step by step with the physical history. These two aspects ofgeological history cannot be divorced. Which is the more fascinating , must depend on the interests of the investigator. Life appeared on the earth perhaps a billion years ago, and, as far as we know, no living creature has...

pdf

Share