Page:Popular Science Monthly Volume 45.djvu/883

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and its times. The diprotodon was in some respects like a wombat, but seems to have been less capable of rapid motion. The spongy texture of the bones of the skeleton indicates that it frequented lakes and marshes. Two species of the fossil have been found in central Australia—one about six feet high and ten feet long, and the other about five feet high and eight feet long. The arid central plains of the present were occupied ia diprotodon times by vast extents of luxuriant forest and richly vegetated districts, well watered by wide rivers. The marsupials were even then the dominant type of life in Australia; lizards were also numerous, and some were of unusually large proportions; megalania, for example, are extinct "guana," from eighteen to twenty feet in length. Alligators and turtles of forms now extinct infested the waters, and among the fishes was the still existing ceratodus. The remains of a varied bird fauna have been preserved in the same deposits. This fauna included some ancestral forms connecting, on the one hand, the wingless birds of New Zealand with the Australian emus, and on the other hand the Australian birds with the New Zealand apteryx. The author was inclined to attribute the disappearance of so many of these forms of ancient life quite as much to senile decay as to altered climatic influences.

Waters of the Colorado Coal Field.—The water supply of the Colorado coal field of Texas, though not abundant as a whole, is represented in the report of Messrs. N. F. Drake and R. A. Thompson, of the State Geological Survey, as usually ample and sufficient for all demands and purposes. Numerous springs burst forth from the strata and many overflowing rivers and creeks traverse the breadth of the region, which afford water unsurpassed for wholesomeness and purity. When sufficient care is exercised in their location, water for drinking purposes can be obtained from wells in nearly all parts of the area, though when bored to excessive depths the water contained is, as a rule, contaminated with salt, oil, and other impurities that exist in the strata. The Colorado, Concho, and San Saba are the only rivers flowing through the district. The Colorado, having for its origin the great springs flowing out from the eastern slope of the Staked Plains, and being re-enforced at every point of its course, furnishes an unsurpassed supply of water to its riparian inhabitants. Except in times of what is called the "red rises," its water is pure and clear. These red rises are caused by heavy rainfalls in the region of the Red Beds of the Permian and Triassic in which the Colorado heads. The beds consist of conglomerates, fine-grained sandstones, and impervious arenaceous and highly calcareous red clays and shales, which disintegrate rapidly under the action of rainfall, and the disintegrated material is borne down by the rapid current of the river. Owing to the fine-grained and impervious nature, especially of the clays, they do not silt rapidly, and the material is held in suspension by the water long after it has passed the limits of the Red Beds. The Colorado flows over numerous little falls and rapids while pursuing its course across the heavy beds of limestone and sandstone which extend from the western boundary of the Permian to the southern limit of the Upper Cretaceous. This shifting turns its every particle again and again to the purifying action of the atmosphere, and the immense beds of stiff and tenacious clays and shales do not impair its clearness. The water flowing over the limestone becomes highly charged with carbonic dioxide in solution, which oxidizes much of the organic matter that may contaminate it, and thus renders it purer. The water of the Concho River is of the same character as that of the Colorado. The San Saba runs about forty miles through the carboniferous formation. Few of the creeks or smaller streams are ever-running, but the majority of them flow except in the driest seasons. Water is obtained in them from numerous large, deep holes, the majority of which remain fllled through the year, and in which it does not become stagnant.

St. Gregory of Nyssa and the Nebular Hypothesis.—In a study, in the American Ecclesiastical Review, of the exegeses by the early Christian writers, especially those of Alexandria and Cæsarea, the Rev. John A. Zahm, of the University of Notre Dame, sets forth that they were the first to propose or develop a true theory of the origin of the world, and to lay the foundations of cosmoganic doctrines that are usually credited to