NEVA LIMESTONE."-Prosser and Beede gave this name to this limestone, it being the name of a station of the Atchison, Topeka & Santa Fe railroad. It lies immediately above the Elmdale formation.

ESKRIDGE SHALES."-From large exposure of these shales near Eskridge, the name was given by Prosser and Beede. It fills the interval between the Neva limestone and the Cottonwood limestone.

COUNCIL GROVE STAGE."

The Council Grove stage is subdivided into two parts, namely, the Cottonwood limestone and the Garrison formation. COTTONWOOD LIMESTONE."-The name Cottonwood limestone or Cottonwood Falls limestone is a commercial term used by the trade for an indefinite period before it was applied to a definite geologic horizon. Extensive stone-quarries were opened up in the vicinity of Cottonwood Falls and stone shipped to many places for erecting costly buildings. In the summer of 1893, Haworth and Kirk made a geologic section up the Neosho and Cottonwood rivers. Their first report was published in January, 1894, and the name Cottonwood Falls limestone formally given to their number 13 of this section. Later, in 1894, Prosser introduced the term "Cottonwood formation," including the Cottonwood Falls limestone and the overlying shale-bed. For the limestone he used the word "Cottonwood" rather than Cottonwood Falls, and in a number of publications since that date has adhered to the name Cottonwood. To simplify matters, therefore, this Survey, in volume III, used the word Cottonwood, which was considered unobjectionable, as the change was so little, and particularly as the commercial name was used indiscriminately, either Cottonwood or Cottonwood Falls. In 1902, Prosser" suggested the name Alma limestone instead of Cottonwood limestone, on account of the name Cottonwood being previously used by N. F. Drake in connection with Texas geology. In a letter, however, to Mr. Bennett, in 1907, Professor Prosser states that "Cottonwood or Cottonwood Falls would be the correct nomenclature." We are not informed of the details for Professor Prosser changing

64. Prosser & Beede, Jour. Geol., vol. X, No. 7, p. 709, 1902. 65. Prosser & Beede, Jour. Geol., vol. X, No. 7, p. 709, 1902. 66. Prosser, Dr. C. S., Jour. Geol., vol. X, p. 709, 1902.

67. Haworth & Kirk, Kan. Univ. Quart., vol. II, p. 112, Jan., 1894. 68. Prosser, Dr. Chas. S., Jour. Geol., vol. III, p. 697, 1895.

69. Prosser, Dr. Chas. S., Jour. Geol., vol. X, p. 711, 1902.

his mind as shown by this letter. The commercial use of the name Cottonwood is so extensive this Survey would be entirely powerless in making a change from Cottonwood to Alma were we to attempt it. Therefore we will continue the use of the name Cottonwood.

GARRISON FORMATION." The Garrison formation, so named by Prosser, fills the interval between the Cottonwood and the Wreford limestone and consists of two members, the Florina shales and the Neosho member.

FLORINA SHALES." The name Florina was given by Prosser and Beede, and was taken from the exposure over the Cottonwood limestone in the quarries near Florina, in the Big Blue valley.

NEOSHO MEMBER."-This is so called by Prosser. He says: "This member was originally termed the Neosho formation, from the excellent outcrop in the Neosho valley near Council Grove. The Florina shales and the Neosho member are now united to form the Garrison formation, on account of good exposures from Garrison south in the Blue valley.

70. Prosser, Dr. C. S., Jour. Geol., vol. X, No. 7, p. 712, 1902. 71. Prosser, Dr. C. S., Jour. Geol., vol. X, No. 7, p. 712, 1902. 72. Prosser, Dr. C. S., Jour. Geol., vol. III, p. 764, 1895.

SUMMARY OF GLACIAL LITERATURE RELATING TO GLACIAL DEPOSITS.

By ALBERT B. REAGAN, La Push, Wash.

GLACIAL DRIFT.

DEFINITION. "Glacial drift is an accumulation of earthy materialsclay, sand, gravel, and boulders-which has been transported by moving masses of ice and deposited over portions of the earth's surface, mostly in the higher latitudes."-Standard Dictionary.

"This aggregation of surface material which overlies different formations indiscriminately, and which is composed of materials which could not have been derived wholly from the underlying rock, is called drift."-Rollen B. Salisbury.

GENETIC CLASSIFICATION.

BASED upon the origin of their formation, glacial deposits

are classed as subglacial, englacial, superglacial, and extraglacial.

SUBGLACIAL DEPOSITS.

The subglacial deposits are those deposits which are dragged along beneath the ice or are formed beneath the ice. They are: Lower till, ground-moraine, or boulder-clay. This is the "hard-pan" clay formation found throughout glaciated regions. It is sometimes called boulder-clay because it contains boulders and pebbles. It is the product of abrasion caused by the stones held in the moving ice-sheet grinding the bed-rock into powder, and the bed-rock, in turn, reducing them to the same material. When the great ice-sheet melted its load was dropped, and in this deposit the coarser and finer materials beneath the sheet were indiscriminately mixed; thus the till or rock-flour.

An examination of this till in Wisconsin gave the following results: It is of medium hardness when dry and slakes readily in water, breaking down into a finely pulverulent mass which has a fair degree of hardness. Under the microscope the grains were observed to have diameters ranging from 10 mm. to 0.003 mm. A very small percentage of the individuals are less than 0.0058 mm. in diameter. The larger grains are fairly well rounded, but the smaller ones have angular outlines.

To use the Standard Dictionary definition for this formation, it is "an accumulation of earthy materials-clay, sand,

gravel, and boulders-which has been deposited over portions of the earth's surface, mostly in the higher latitudes."

GUMBO. This formation is the stratified portion of the lower till of the Mississippi valley. It is a granular, adhesive clay, often several feet in thickness. It is not such a continuous deposit as the overlying loess, there being many places where the loess rests directly upon typical till. Like the loess, though, it seems to bè independent of contour lines in its distribution. Its color varies from light gray or ash to nearly black. The black portions are heavily charged with humus and in places present the appearance of swamp muck. It is from this clay that the black soil so often seen at the base of the loess is usually developed. This gumbo clay contains a few pebbles, much less than the typical till or loess. cording to Mr. Leverett, these deposits may be of aqueous origin; but such an hypothesis cannot be confidently put forward as a solution.

Ac

DRUMLINS.-A drumlin is a smoothly rounded hill. Mounds or hills of this sort are found all over the glaciated region, from Maine to the Rocky Mountains. Their origin is in doubt. Prof. G. F. Wright' and others believe that during the final melting of the ice the surface would melt unequally, since the large boulders and deeper masses of till would partially protect the ice beneath them from melting, and that, consequently, there would be much lateral sliding of till into the depressions thus formed on the ice surface, which, when the glaciers disappeared, would remain as drumlins. But it is difficult to conceive how smoothly rounded hills in such large numbers and such great size could result from this process. Moreover, some of the masses of thoroughly glaciated matter are long ridges parallel with the glaciation, masses still more difficult of explanation as being due to accumulation in surface hollows of the ice.

Prof. N. S. Shaler' believes that these hills are the remains of a former sheet of till of which the greater part has been eroded by the sea waves, but to this opinion there are many objections: First, these deep masses of till are sometimes one mile or more from any similar mass. The amount of erosion required is enormous. Second, had a great mass of till been eroded, most of the larger stones would now remain as broad

1. Wright, Ice Age of North America.

2. Bull. Geol. Soc. Am., vol. 10; also Shaler and Davis, Glaciers.

sheets in the valleys or as terraces on the hillsides, a phenomenon which does not exist. Third, had the till been eroded in the manner supposed above, the erosion must have occurred before the deposition of the marine beds; and these beds, in turn, would preserve the beach gravels beneath them from erosion. No such rolled gravels now exist beneath the clays. Fourth, had there been such an erosion of the till, the kames and marine deltas would not have escaped in such a good state of preservation. Fifth, the lenticular sheets of till on the northern slopes of hills must have substantially the same origin as drumlins themselves. Yet there are multitudes of these hillside lenses in regions where no genuine waterwashed gravel is to be found.

Another theory is that drumlins are the remains of a former sheet of till irregularly eroded by the glacier. But it is difficult to see how a glacier can deposit till and not at the same time deposit glacial gravel.

In speaking of the drumlins of New Hampshire, Emerson says: "Could one raise the stratum of stony clay which overspreads the valleys, as one lifts a plaster mask from the face, it would be found that its under surface had been exactly molded to every line and curve in the rocky substratum; but its upper surface would have the effect of a comic mask, swelling with unequal thickness over every prominent feature; distorting and concealing its true form, and sending up great protuberances due wholly to a thickening of its own mass and not molded on any projecting ledge below. The protuberances formed thus by local thickening of the sheet appear now as drumlins, massive domed hills, in shape like an inverted canoe, with their long axes pointing in the direction of glacial motion from north to south."

Hitchcock and Wright have thought drumlins to be, perhaps, the material of terminal moraines swept over and massed in these peculiar forms by subsequent farther advances of the ice-sheet.

King and Dana have conjectured that drumlins, at least in some cases, were made by superglacial streams, charged with drift, pouring through crevasses or a moulin to the land surface, there depositing their drift, which afterwards by the outflow of the ice would be subjected to its pressure and sculpturing.

3. Monograph 29, p. 545.