1865, June 10. King and Rowney (Profs.), Question the organic nature of Eozoön, while Dr. Carpenter sustains it, supported by the authority of Milne-Edwards.

S

1866, Feb. 10. Carpenter (Dr. W. B.), Announces Eozoön from Australia and Bavaria, and controverts the position of Profs. King and Rowney. Noticed in Amer. Jour. Sci. [2], xli., 406.

1866, Aug. King and Rowney (Profs. ), "On the so-called Eozoönal rock,' denying its organic character. Quar. Jour. Geol. Soc., Lond., xxii., pt. ii., 23. Their position is controverted in the same No. Their

66

Summary" is reproduced Amer. Jour. Sci. [2], xliv., 375.

1866. Gümbel (Dr.), "Occurrence of Eozoön in East Bavarian primitive rocks." Sitzungsberichte d. K. Acad. d. W. in München, i., 1. Reproduced Quar. Jour. Geol. Soc., Lond., xxii., pt. i., p. 185. ticed Amer. Jour. Sci. [2], xliii., 398. Confirmed by Carpenter,

No

Proc. Roy. Soc., No. xciii., p. 508.

1867, May. Dawson and Logan. Describe new specimens of Eozoön from

Tudor, C. W. Quar. Jour. Geol. Soc.

1867. Carpenter (Dr. W. B.), Reasserts organic nature of Eozoön in opposition to King and Rowney. Proc. Royal Soc., No. xciii., p. 503. 1867. Pusirevski (Prof.), Reports Eozoön Canadense at Hopinwara, Finland. Bull. Acad. St. Petersburg, x., 151. Noticed Amer. Jour. Sci. [2], xliv., 284.

1867, Nov. Dawson (J. W.), Notes on Eozoön from Tudor, C. W., from Long Lake and Wentworth, and from Madoc, with remarks by Dr. W. B. Carpenter. Amer. Jour. Sci. [2], xliv., 367. Republished Amer. Jour. Sci. [2], xlvi., 245 (Sept., 1868).

NOTE III., page 76.

As the reader may frequently desire to refresh his memory in reference to the order of superposition of the great groups of strata, the following table is appended for reference. The groups follow each other in the natural order of superposition.

CLASSIFICATION OF THE STRATIFIED ROCKS OF NORTH AMERICA.

CLASSIFICATION OF THE STRATIFIED ROCKS OF NORTH AMERICA (Continued).

NOTE IV., page 132.

The term Catskill group is employed in this connection in a sense greatly restricted from that in which the New York geologists originally employed it, since it has been shown that the principal portion of the so-called Catskill strata of the Catskill Mountains is really a prolongation of the Chemung rocks of the southern interior of the state; and for this reason, the original sense of the term is no longer admissible. The term thus stands as the designation of a series of strata which does not form a naturally restricted assemblage, and must drop out of use.

In parallelizing the "Catskill" (thus restricted) and the "Marshall" with the lower part of the Mountain Limestone of Europe, and at the same time suggesting their synchronism with the "Old Red Sandstone," I employ the latter term in its restricted and original sense, not as comprehending the whole recognized Devonian of the Old World. It is farther not unlikely that the parallelism ought to be restricted to the "Yellow," "White, and "Red" sandstones and conglomerates (Marwood and Petherwin beds) of the Old Red series, which, according to admissions made from time to time by Murchison and others, exhibit almost decisive affinities with the Carboniferous age. See Quar. Jour. Geol. Soc., London, vol. ix., p. 23.

NOTE V., page 139.

Allusion is here made to one of the mines at Lasalle, Illinois. This by no means exemplifies the greatest depth to which mining operations have been carried. The mine at Duckenfeld, in Cheshire, England, is probably the deepest coal mine in the world. A simple shaft was sunk 2004 feet to the bed of coal, and by means of an engine plane in the coal-bed, a farther depth of 500 feet has been attained, making 2504 feet to the bottom of the excavation. At Pendleton, near Manchester, coal is worked daily from a depth of 2135 feet; and the Cannel coal of Wigan is brought from 1773 feet below the surface. Many of the Durham collieries are equally deep, and far more extensive in their subterranean labyrinths.

The engine shaft of the Great Consolidated copper mines in Cornwall reaches the depth of 1650 feet, and the length of the various shafts, adits, and galleries exceeds 63 miles. Dalcoath tin mine, in Cornwall, is now working at more than 1800 feet from the surface. The famous silver mine of Valenciana, Mexico, is 1860 feet deep. The Hohenbirger mines in the Saxon Erzegebirge, near Freiburg, are 1827 feet deep, and the Thurmhofer 1944 feet deep. The depth of the celebrated mine of Joachimsthal, in Bohemia, is 2120 feet. The Treṣavean copper mine in Cornwall is 2180 feet. The workings of the Samson mine at Andreasberg, in the Harz, have been prosecuted to the depth of 2197 feet. At Rörerbühel, in Bohemia, there were in the 16th century excavations to the depth of 3107

feet, made before the invention of gunpowder. The greatest depth to which human labor and ingenuity have as yet been able to penetrate is 3778 feet, in the old Kuttenberger mine in Bohemia, now abandoned. This depth, as remarked by Humboldt, is about eight times the height of the pyramid of Cheops or the Cathedral of Strasburg.

The deepest excavation in the United States is probably that of the Minnesota mine near Ontonagon, Lake Superior, which descends upon a copper-bearing lode to the depth of over 1300 feet. The Quincy mine at Hancock is 900 feet deep. The deepest mine in California is said to be the Hayward Quartz mine in Amador county, 1200 feet deep. The deepest excavations on the Comstock lode, Nevada, are 700 feet.

Mining excavations frequently extend from half a mile to a mile under the sea. In these gloomy subterranean and submarine passages, where, in some cases, one or two hundred feet of sea-water rest upon a slaty roof but three or four feet thick, the low moan of the waves can be continually heard above the miner's head, and in time of storms the howl becomes terrific and intolerable. The great adit for the discharge of the waters of the Gwennap tin mines in Cornwall exceeds 30 miles. In 1864, a tunnel 14 miles in length was completed in the region of the Harz mines, Brunswick, for the drainage of the district. A similar tunnel, 15 miles in length, designed for the drainage of the Freiberg district, has been in progress for several years. The Sutro tunnel, designed for the drainage of the mines located upon the Comstock lode, Nevada, is to be 19,000 feet in length, 12 feet wide, and 10 feet high, and will cost between four and five millions of dollars.

The great "tunnel" at Chicago, through which the city is supplied with pure water from Lake Michigan, is 10,567 feet long, five feet wide, and five feet two inches high, and at the shore extremity communicates with a vertical shaft 82 feet below the lake-level, and at the other extremity with a crib and shaft 66 feet below the lake-level.

NOTE VI., page 185.

As the Archeopteryx, or bird-reptile, is one of the most remarkable relics of the ancient world, and has but recently been brought to light, I append some references to sources of information upon the subject: Prof. Wagner first announced the discovery to the Royal Academy of Sciences of Munich in 1861; H. Herrman von Meyer described it in "Jahrbuch für Mineralogie," 1861, p. 561; Wm. H. Woodward, in "Intellectual Observer," Dec. 1862 (with plate); Prof. J. D. Dana, in "Amer. Jour. of Science and Arts," 2d ser., xxxv., May, 1863, p. 129, and "Manual of Geology," Appendix to later editions; Prof. R. Owen, in "Philosophical Transactions," cliii., part i., 1863, p. 33, pl. 1 to 4.

NOTE VII., p. 228.

I have given in the text the usual explanation of the phenomena of the glacial epoch. The theory of northern elevation, however, as the sole or principal cause of continental glaciers, has never been regarded, by many geologists, as completely satisfactory. Within a few years renewed attempts have been made to connect these phenomena with astronomical changes of a secular character.

At sundry epochs in the history of the world, agencies seem to have arisen which brought into existence and transported over considerable distances vast quantities of rounded pebbles and finer detrital materials. In some cases-as in the Niagara, Permian, and Upper Miocene periods— smoothed and striated rock-surfaces have been discovered, similar to those which are generally attributed to glacier action. In the intervening periods evidences of tropical temperature present themselves. The suggestion has therefore been made that more than once in the history of the world—perhaps at somewhat regular intervals widely removed--the northern portions of the continents have been visited by a reign of frost.

To account for these apparently secular phenomena, new investigations have been made upon the effects of the secular variations in the longitude of the equinox, the eccentricity of the earth's orbit, and the obliquity of the ecliptic. This is not the place to enter into an exposition of the discussions which have arisen. I may, however, simply explain the nature of the relation which subsists between terrestrial climates and the cosmical changes alluded to.

1. As to the variation in the eccentricity of the earth's orbit, it is evident that when the northern hemisphere has its winter in perihelion during the time of greatest eccentricity, the amount of glaciation must be considerably less than when the same hemisphere has its winter in aphelion during the time of greatest eccentricity.

2. As to the variation in the obliquity of the earth's axis, it appears that when the obliquity is greatest, the winter temperature of the polar regions can not be much severer than when the obliquity is least since when the sun is below the horizon it is immaterial whether it be two degrees or ten below-while the summer temperature of the polar regions will be increased by the whole increase in the verticality of the sun's rays. The effect, therefore, of an increase in the obliquity of the earth's axis will be to diminish the average glaciation of the polar regions.

3. Suppose now the minimum glaciation of the polar regions, so far as due to obliquity, to occur at the time when the northern hemisphere experiences minimum rigors of climate through the effect of increased eccentricity; the conjunction of these two minima of cold in the north polar regions would, it is thought, remove the ice cap, and effect conditions of climate such as prevailed when Greenland, in the Miocene period, supported trees of tropical nature and luxuriance.