4. These conditions all reversed would produce a maximum of glaciation in the north temperate and polar regions such as evidently existed at the beginning of the Post Tertiary period. It is probably within the power of physical astronomy to calculate the epochs at which these maxima and minima have occurred. It is, however, a problem of considerable difficulty, involving, as it does, the rate of precession of the equinoxes, the proper motion of the apsides, and the secular change in the obliquity of the ecliptic, none of which data are perfectly constant. According to recent determinations, the equinox completes a revolution in 25,868 years. The apsides move forward to meet the equinox, so that perihelion has the same longitude once in 21,066 years. The obliquity of the ecliptic returns to the same value in about 100,000 years. M. Adhemar has based an explanation of the occurrence of glacial periods upon the climatic effects of the precession of the equinoxes alone. As the earth's axis is inclined to the ecliptic, the hemisphere which has its winter in aphelion is not only farther from the sun than the other hemisphere during its winter, but also experiences a winter having about eight days longer duration. The excess in the duration of its winter is partly caused by the slower motion of the earth on that side of the equinoxes which embraces the upper apsis, and partly also by the greater length of the path on that side. This hemisphere is therefore subjected to an excess of cold. For reverse reasons, the other hemisphere enjoys more than the mean warmth. In consequence, however, of the gyration of the axis in a period which Adhémar takes at 21,000 years, it follows that at the end of 10,500 years the hemisphere which had been turned away from the sun at aphelion becomes turned toward him. In other words, the climatic inequalities of the two hemispheres become reversed. That hemisphere which for 10,500 years had been subjected to excessive glaciation, now enjoys excessive warmth, and that which had enjoyed excessive warmth is visited by excessive cold. There are, therefore, two great seasons for each hemisphere during the progress of the Annus Magnus, or Great Year. The summer has a duration of 10,500 years, and the winter an equal duration. One thing farther should be remarked in connection with the accumulation of masses of ice and snow about either pole, from whatever cause the accumulation proceeds. Such an accumulation must necessarily change the position of the centre of gravity of the earth-mass. That centre must move toward the pole thus burdened. The fluent waters upon the earth's surface, free to adjust themselves in equilibrium about the centre of gravity, must change their distribution as the place of the centre of gravity changes. During the glaciation of the southern hemisphere, the waters will accumulate about the south pole; and during the glaciation of the northern hemisphere, they must accumulate about the north pole. These alternating accumulations of the waters are adequate. It has been calculated, to account for the last submergence of the northern hemisphere during the Champlain Epoch. The submergence of the southern polar lands is now in progress. Should the connection of “the glacial period"—and of other glacial periods more ancient-with cosmical conditions, be satisfactorily established, it seems to me that we are here furnished with a hopeful means of giving greater precision to the calculus of geological time. For detailed information on these questions, see Croll, Philosophical Magazine for August, 1864, and February, 1867; Transactions Geol. Soc., Glasgow, April, 1867; Revue des deux Mondes, 1847, etc. NOTE VIII., page 287. As the records of the flowing wells of Oil Springs constitute one of the most remarkable chapters of the history of Petroleum, I append here a list of them, made from personal examination and research. In this list, "Sub." stands for subdivision, "R." for range, "L." for lot, and "Con." for concession. Former Flowing Wells at Oil Springs, township of Enniskillen, Ontario. Depth in feet. Yield in bbls. Trifling. 3 Finn & Brown-S. E. part L. 17, Con. 1... 130 Campbell-W. & L. 19, Con. 2...... 132 Bennett Brothers... 136 Chandler-Sub. 33, R. 2, L. 18, Con. 2. 163 Sanborn & Shannon-Sub. 13, R. C., L. 18, Con. 2. ... 164 Bradley-Sub. 13, R. I., L. 18, Con. 2.. 167 Webster & Shepley-E. part L. 18, Con. 2.. 170 Leavenworth-Sub. 7, R. C., L. 18, Con. 2..... 600 300 500 200 500 100 2000 150 800 3000 200 3000 250 250 400 2000 1000 2000 3000 6000 500 Depth in feet. ... 170 Culver-Sub. 7, R. C., L. 18, Con. 2.. 173 Allen-Sub. 32, R. 5, L. 17, Con. 2.. 175 Barnes-Sub. 36, R. 5, L. 17, Con. 2. 178 Petit-W. L. 19, Con. 2.. • 180 George Gray-Sub. 32, R. I., L. 17, Con. 2.. 196 Nelson-Sub. 29, R. 2, L. 17, Con. 2. 212 Fiero-Sub. 1, R. 4, L. 19, Con. 1... 237 Black & Mathewson-Sub. 12, L. 17, Con. 1....................................... Yield in bbls. 200 2000 300 3000 150 500 1200 6000 6000 7500 NOTE IX., page 396. The thoughts embodied in this and the five following chapters were first shadowed forth by the author in the Michigan Journal of Education in 1860. They were more fully elaborated in the Ladies' Repository for November and December, 1863, and January, 1864. Many thoughts and conceptions which were then original appear to be now but the echoes of Mayer, Helmholtz, and others. This is particularly the case in reference to the doctrine of solar refrigeration. That doctrine, then entirely new to the writer, was put forth with much apprehension. The publication of Mayer's papers in Silliman's Journal (vol. xxxvi., p. 261; xxxvii., p. 187; xxxviii., p. 239, 397) in 1863 and 1864 afforded the writer the first exact basis for conclusions which he had already reached. The later researches of others have served to give a scientific sanction to statements which at one time might have been regarded as little more than vagaries of the imagination. NOTE X., page 404. Such, at least, is the generalization put forth by Müncke, Mrs. Somerville, and other physicists. It is apparently founded on reports of observations made by Scoresby and Parry in the Arctic Ocean, and by James Ross in the Antarctic. M. Charles Martins, however, a highly competent authority, denies that any such increase of temperature in the deeper arctic waters exists. Nothing of the kind was observed by le Contre-Amiral Coupvent des Bois in the voyage of the corvettes Astrolabe and Zélée; 'nor in the soundings made on the two voyages to Spitzbergen with the corvette Recherche. On this subject, see Gehler's Physikalisches Worterbuch, t. vi., p. 1685; Somerville's Connection of the Physical Sciences, Am. ed., p. 245; May er, Celestial Dynamics, in Correlation and Conservation of Forces, p. 311; Voyage en Scandinavie et au Spitzberg de la corvette la Recherche, Géographie Physique, t. ii., p. 279; Annales de Chimie et de Physique, 3o Série, t. xxiv., p. 220, 1848; Comptes Rendus, t. lxi., p. 836. NOTE XI., page 368. The condensed statement in the text conveys a wrong impression. There are two cones at the mouth of the Tinière-a lower, or newer, and an upper, or older one. Morlot calculated the lower to be from 7490 to 11,000 years old, and the age of both he estimated at 96,000 to 143,000 years. Andrews calculates the age of the lower to be from 4265 to 4876 years. He makes the antiquity of the upper greatly less than Morlot, though he does not find the data for a numerical statement. Human remains are only known in the lower cone; the age of the upper is commonly supposed to measure the duration of post-tertiary time, though not unlikely it reaches back into tertiary time. On this subject the reader may readily refer to Smithsonian Report, 1860, p. 340; Ib., 1862, p. 310; Amer. Jour. Sci. [2], vol. xlv., p. 187. NOTE XII., page 179, fig. 71. In adopting this illustration from the pages of a popular French writer, it might have been better to have adapted the view of the Ichthyosaur to our present positive knowledge of its organization, by omitting the waterspouts. Though this reptile possessed well-established cetacean affinities, we are not certain of its being so much of a whale as the figure indicates. NOTE XIII., page 204. The first restorer of the Zeuglodon was Mr. S. B. Buckley, now of Austin, Texas, and formerly geologist to that state. He discovered the first nearly complete skeleton upon the plantation of Judge Creagh, in Macon County, Ala., and exhumed it in January and February, 1841. He made a restoration of it on the spot. Its length was seventy feet. Accounts of these discoveries were published in the Amer. Jour. Sci., April, 1843, and July, 1846. Fifty feet of another vertebral column were also discovered, but left on the premises of Judge Creagh. These vertebræ were subsequently found by Dr. Koch, who made numerous additions, and produced semi-factitious Hydrarchos, to which reference is made in the text, and which, after exhibition in New York, was taken to Berlin and sold. Buckley's original specimen was sold for $200 to Dr. E. Emmons, who published some account of it in the Quar. Jour. Agr. and Sci., and then sold it for $900 to Dr. Warren, of Boston. It still exists in the private Warren Museum. |