plateau, which has an elevation of a little over 3,000 feet above the sea-level. Suddenly, just before reaching Colfax, a sharp bend in the line, at a place called Cape Horn, brings the road bed just on to the edge of the cañon of the North Fork of the American, down into and along which there is an unobstructed view for eight or ten miles, the bottom of the cañon being about 1,600 feet below the level of the road. The effect of the scene presented to the eye from this point is extremely striking, because the spectator has not been prepared, by anything which he has previously seen, to expect to find the flanks of the Sierra so deeply cut into by the streams, which seem of insignificant size as compared with the immense troughs at the bottom of which they run."

The course of the old channels are but partially made out. They are the objects of search by the miner, since the richer auriferous gravels lie along them, directly upon the bed rock. But although often of great depth and distinctness, they are only partially uncovered in the mining operations, and the facts are not examined and recorded when open to view, so that " we can never expect to know exactly what were the relations of the various parts of the old river system to one another." The lava-floods and beds of volcanic ashes and other material over the gravels prevent even the miner from exploring a large part of the old surface, though hydraulic mining and tunnelling have been pushed with great energy where it would pay. The volume gives a detailed account of observations on the gravel deposits and the bed-rock made for the Survey (on appointment of Professor Whitney) by Mr. W. A. Goodyear and Professor W. H. Pettee, which are illustrated by colored maps of the areas of lava and gravel.

Because of its special interest we copy here one of the sections of the Sonora, or Tuolumne County, Table Mountain, from Plate

F. It represents (on a scale of 300 feet to the inch) the cap or table-top of basalt (b) over 200 feet thick, overlying sand-beds and shaly material (c), with an auriferous gravel deposit (g) at the lowest part, and these resting on the nearly vertical metamorphic schists (d). The surface of the schists rises to the left, making there the "rim" of the old channel; and a tunnel (t) is represented passing through this rim to the gold-bearing gravels, a common method of search, though attended with large expense and not always successful.

A notice of the fossils of the gravels, including its Human relics, is deferred to another number.

2. Richthofen's Theory of the Loess, in the light of the Deposits of the Missouri; by J. E. TODD, of Tabor, Iowa.-This memoir, read before the last meeting of the American Association, is a strong argument, well-sustained by facts drawn mainly from the region of the Missouri River, against the wind-drift theory of the loss. The writer observes that although the mollusks are mainly terrestrial, "some semi-aquatic species, as Succineas and Helicinas are abundant from top to bottom [in the loss of the Missouri], and the decidedly aquatic Limnea humilis is quite abundant in the Upper loss of Western Iowa." Further," the small size of the Limneas and absence of Physas in the latitude of Iowa, may be considered as indicating that the waters were cold, while the occurrence of numerous land-shells of species still inhabiting the region, indicates that the lands were more moist with their temperature not differing greatly from the present." Root-marks occur in much of the loss but are mostly confined to its upper portion, being rare at a depth exceeding thirty or forty

feet.

3. Tertiary in Massachusetts Bay.-Many fossiliferous bowlders have been found by Mr. WARREN UPHAM, as reported by Mr. W. O. CROSBY in the Proceedings of the Boston Natural History Society for February last, at different points in the Drift of Truro on Cape Cod. They include Venericardia planicosta, a Lower Eocene species of Virginia, and two others of the same genus, one probably P. parva, described by Lea, from Alabama, three species of Ostrea, one apparently 0. divaricata Lea, of the Alabama Middle Eocene, an Anomia which is probably A. tellinoides Morton, a Plicatula near P. filamentosa Conrad, of the Alabama Eocene, besides several other species of shells, and remains of Echinoderms and a Galaxea-like coral. Mr. Crosby concludes that the Tertiary formation, which was the source of these fossils, now forms the floor of Massachusetts Bay somewhere to the northward of Cape Cod. These facts derive additional interest from a comparison with those announced by Professor Verrill, in the number of this Journal for October last, with regard to submarine Tertiary along George's Bank and Grand Bank. The species found are wholly different.

4. Report of Progress in the Juniata District on the Fossil Iron Ore-beds of Middle Pennsylvania, by JOHN H. DEWEES; with a Report on the Aughwick Valley and East Broad Top District, by C. A. ASHBURNER. Second Pennsylvania Geological Survey. Harrisburg, 1878.-This Report is noticed by title only on page 262 of the last volume of this Journal. It opens with a Preface by Prof. Lesley, Director of the Survey, giving a general sketch of the formations in which iron-bearing beds occur, the most important of which are those of the Clinton group, and the Marcellus. Mr. Dewees presents the facts with full details of the stratification. Excellent sections of the folded rocks are given

which are by Mr. Ashburner, and are continued in his portion of the volume; and these are supplemented by large and fine colored sections and maps in a portfolio. This geologist, moreover, describes the Silurian and Devonian rocks from the Trenton to the Hamilton in the valley of the Juniata, from Lewistown in Mifflin County to Mount Union in Huntingdon County; and the account has special interest since it illustrates the typical structure of Central Pennsylvania. A carefully measured section from the bottom of the Trenton to the top of the Mahoning Sandstone, or top of the Lower Productive Coal measures, shows a thickness of 18,397 feet-and in this long section, 68.9 feet is the average thickness for the 267 separate strata included. A catalogue of specimens, and another of heights above the sea-level are given, in an Appendix to the Report. The former is on a plan worthy of imitation. Mr. Ashburner places on the labels of his specimens (besides the geographical position) the number of the stratum, the distance in feet from the lower limit of the same, and also the dip of the beds; so that any future investigator will be able to take up any part of the work for revision or for further study.

5. On the Geology of Gibraltar.-The following facts are from a paper by Professor A. C. RAMSAY and JAMES GEIKIE, in the Quarterly Journal of the Geological Society for August, 1878.

-More than three-fourths of the promontory of Gibraltar consists of a grayish white bedded limestone, containing occasional casts of Rhynchonelle and encrinal stems, the former closely like R. concinna, a species abundant in the Cornbrash and Coral Rag. The limestone is overlaid by shales of various shades of color, with some thin calcareous beds, which have afforded no fossils. The dip of the rocks is in general over 40°, and in some parts 75° and higher. Upon these beds there are superficial deposits. The oldest is a limestone breccia, covering a large area in the district of Buena Vista and Rosia, and in the vicinity of the South Barracks; it is unfossiliferous. The authors attribute the origin of the limestone fragments of which the breccia consists to the frosts or cold of the Glacial era. The mean temperature of the coldest month (February) is now 54.2°, and the lowest point reached in the six years from 1853 to 1859 was 32.70; and no debris is now forming from such a cause or any other. Besides these surface breccias or conglomerates there are also bone-breccias in caves and fissures. The famous bone-breccia at Rosia Bay occupies a vertical fissure of erosion in the above-described surface breccia, while the Genista breccia occurs in a true cave.

The promontory bears evidence of different sea-levels in terraces or platforms cut in the solid rock, surmounted sometimes by calcareous sandstones. The Europa Flats is one of these sea-levels on the southern portion of the promontory; it extends from west to east for 1650 feet, and it averages 115 feet above the sea-level, though sloping up from 90 feet to 150 feet. It appears also at other points. The calcareous conglomerate over it contains some

remains of Mediterranean species and is evidently of marine shore origin. Another such terrace has a height not less than 250 feet; a third, about 830 yards in length and over 330 broad, is 370 feet above the sea. In the front of the same cliffs at a height of 170 feet an oyster-bed was formerly visible.

Among the species of Mammals identified by Messrs. Busk and Falconer from the Genista cave, there are Rhinoceros hemitœchus, Horse, Boar, Cervus elaphas, C. dama, Ibex, Bear, Wolf, Hyana crocuta, Lion, Panther, Lynx, etc., and these authors concluded that, at the time these animals were living, Europe and Africa were at some point united across the Mediterranean. With this in view, the succession of Quaternary events in Gibraltar is given as follows:

(1.) Great unfossiliferous limestone-agglomerate of Buena Vista, etc.-Land of greater extent than now; winters very cold; Gibraltar apparently not tenanted by the Quaternary Mammalia.

(2.) Caves and fissures with bone-breccia.-Land of greater extent than now; Europe and Africa united; climate genial; immigration of the African Mammalia.

(3.) Platforms or terraces of marine erosion (in part), calcareous sands, etc.-Depression of the land to the extent of 700 feet below present level; movement interrupted by pauses of longer or shorter duration; climate apparently much the same

as now.

(4.) Platforms of marine erosion (in part); Alameda Sands; formation of sand-slopes on east coast, as at Monkey's Cave; mammalian remains under beach or later limestone-agglomerate (perhaps cave-deposits in part).-Reëlevation; land of greater extent than now (Africa and Europe perhaps reunited); climate probably genial.

(5.) Later limestone-agglomerates resting upon and obscuring erosion-terraces and sand-slopes, etc.- Geographical conditions probably same as during part of 4; winter considerably more severe than now.

(6.) The present.-Characterized by the absence of the action of frost.

On the conclusion of the reading of the paper, the statement was made by Admiral Spratt, that to the westward of Farifa Point a submarine ridge exists which nowhere exceeds 130 fathoms in depth; so that an upheaval of about 800 feet would connect the two continents by dry land.

6. Etudes Synthétiques de Géologie Expérimental, par A. DAURRÉE, Membre de L'Institut, Inspecteur Général des Mines, etc. Première Partie, Application de la Méthode Expérimentale a l'étude de divers Phénomènes Géologiques. 478 pp. 8vo. Paris, 1879. (Dunod).-The admirable researches in Experimental Geology of Professor Daubrée have in part been briefly announced in former volumes of this Journal. The work just issued under the above title contains these results in full, and, in addition, those

of more recent researches. After a historical introduction, the author gives an account of his observations illustrating the history of metalliferous deposits, and especially those of tin, lead and platinum, bringing in a wide range of facts relating to such deposits, and among them prominently his remarkable discoveries of a large number of ores of modern formation made out of a lot of Roman coins at the Warm Springs of Bourbonne-les-Bains, and also of similar formations at some other localities; and, after stating the facts, the chemistry of the phenomena and the geological inferences from the facts are learnedly presented.

Professor Daubrée's next subject is Experimental illustrations of the origin of metamorphic and eruptive rocks. Under this head numerous observations are reviewed, and in addition the results of his own experiments, with regard to the formation of silicates by means of superheated water: such as the transformation of glass into a hydrated silica and crystallized quartz, the glass sometimes containing minute well-formed crystals of pyroxene (figures of which crystals as well as of those of quartz are given); and the formation of zeolites (chabazite, apophyllite, etc.) at Plombières, and at other warm baths inside of bricks, along with opal, chalcedony, tridymite, aragonite, and other species. Volcanic phenomena are next illustrated by experiments, and with this chapter the first section of the volume closes. The second section is occupied with mechanical problems: (1) the making of sand-beds and clay-beds, showing for example, the effects of the trituration of feldspar in water (some loss of alkali taking place in pure water and "incomparably less" with salt water), in carbonated waters, etc.; (2) the scratching and polishing of rocks, their flexures, fractures, faults, jointed structure, slaty cleavage and schistosity, and the distortions of fossils and pebbles; and (3) the production of heat in rocks by mechanical methods. All the modes of experimenting are described in detail, and illustrated by figures; many of the results obtained in his mechanical processes are also figured, and their bearings on geological problems are fully and ably discussed. The work is thus in every part a rich contribution to the science of geology; moreover it is made highly attractive by its style of publication and the beauty of its illustrations.

7. Rocks under London.-In the Artesian boring in the Tottenham Court Road, according to a paper by Professor Prestwich (Quart. J. Geol. Soc., Nov., 1878), it was found that the Chalk had a total thickness of 652 feet, the Upper Greensand 28 feet, the Gault 160 feet. Below this was a bed three to four feet thick of phosphatic nodules and quartz pebbles; and then a calcareous stratum, more or less sandy, and part of it oolitic, sixty-four feet thick, which was shown by its fossils to represent the Lower Greensand. Underneath, at a depth of 1064 feet, the bore-hole entered mottled red, purple and greenish shales, to some extent calcareous, having a dip of 35°, and these continued for eightyfive feet; they afforded the fossils Spirifer disjuncta, Rhynchonella cuboides, and other Devonian species. The rocks