Mat 10, 1918] 



SCIENCE 



469 



parenfly l>arren in chert are: the Silurian forma- 

 tions, and limestones in the upper portion of the 

 Pennsylvanian. The Greenbrier limestone is no- 

 tably poor in flint. The Kanawha Black Flint oc- 

 curs in two lithologic phrases — a high-silica, low- 

 alumina, compact phase, and a phase slightly 

 lower in silica and higher in alumina which has a 

 ' ' slaty ' ' structure. Fossils of species which pos- 

 sess lime shells have been leached out before the 

 deposition of the silica. Replacement of calcium 

 carbonate has played an unimportant role in the 

 formation of the flint. Depositions of silica by 

 descending surface waters in the pores of a car- 

 bonaceous and highly silieious rock has resulted in 

 the formation of a dull, black, compact chert or 

 flint. Absence of original silieious ooze is inferred 

 but not proven. Tilting of the strata has enabled 

 solutions to migrate along the dip, increasing 

 silification. The black flints of the Pennsylvanian 

 were used by the Indians in the manufacture of 

 arrow heads and implements. They have been scat- 

 tered over many counties beyond the flint out<!rop. 

 Flint from limestone formations often contains 

 suflicient lime to form a compact surface when 

 used in road building. Chert beds in limestone val- 

 leys form ridges upon which apples and berries 

 grow especially well. 



The determination of the stratigraphic position 

 of coal seams by means of their spore-exines : 

 Reinhardt Thiessen. 



There has thus far been found no index by means 

 of which coal from different mines or from different 

 bore holes may be correlated, or by means of which 

 the position of a seam may be determined. The 

 spore-exines in coal promise to furnish such an 

 index. The coal from every seam, thus far ex- 

 amined, contains one or more types of exines that 

 are characteristic or predominant or both of each 

 bed, by means of which the coal may readily be 

 identified and the position of its bed be deter- 

 mined. Spore-exines are very prominent in coal, 

 are easily recognized and have retained all their 

 original characters by means of which each type 

 may easily be defined. The coal of the Pittsburgh 

 seam contains at least one type of exine that is 

 both predominant and characteristic of that seam. 

 Similarly the coals from Sipsey, Alabama, Black 

 Creek bed; Carbon Hill, Alabama, Jugger bed; 

 Shelbyville, 111., bed No. 2, and from Buxton, la. 

 Each contains at least one type that is both the 

 predominant and the characteristic exine. Some 

 of these have, besides these, at least one other 

 type that is characteristic of the seam, although 

 not the predominant one. Bed No. 6, of Illinois, 



contains at least one tyjie that is characteristic of 



that bed, and probably more. 



The HolmesviUe, Ohio, glacial terrace and moraine: 



G. G. Cole. 



The village is situated on a large terrace sur- 

 rounded on all sides by low ground, with a swamp 

 separating it from the recessional moraine half a 

 mile south. The terrace is very steep on the north 

 and while quite flat slopes gradually to the south. 

 Well-washed coarse gravel is found on the north- 

 west higher corner, the southern being fine ma- 

 terial and sand. A peculiar arrangement occurs in 

 the terrace: gravel of 74 per cent, local origin at 

 the top, a belt of large boulders at a mean depth 

 of 8 feet, mostly granitic, with fine gravel and 

 sand beneath. This indicates a complicated origin 

 for the terrace. The moraine is a recessional one, 

 located five miles back from the terminal moraine 

 at Millersburg, Ohio. It is of great size and likely 

 to be overlooked as a glacial feature on that ac- 

 count. It is crescent-shaped with concave side 

 toward the HolmesvUle terrace, having its two 

 horns west and northeast of the terrace a mile 

 apart. Numerous kettles with a kettle pond are 

 found on its surface and border. These have been 

 well preserved by virgin forests recently removed. 

 Drift material 31 per cent, foreign, some Cornifer- 

 ous limestone from Lake Erie region being found. 

 The terrace structure is accounted for by suppos- 

 ing an impounded lake between the moraine and 

 a stage of ice recession to present site of north 

 edge of terrace. The lower layers of terrace de- 

 rived from the sediment of this lake; the boulder 

 bed from the melting of the receding ice. The 

 subsequent drainage of the lake around the west- 

 ern horn of moraine, caused the debris to collect in 

 front of the face of ice and increased by material 

 brought out from an interglacial tunnel at north- 

 west corner of terrace, involving an outwash plain 

 distributed as upper surface of the terrace. Steep 

 sides caused by a rapid abandonment of the valley 

 north of the terrace. 



Diverse ancestry of great basin lal-es: Charles 



Keyes. 



Explanation of the former existence of desert 

 lakes of great size in western America on the basis 

 of once greater regional hmnidity becomes notably 

 inadequate when it is realized that hardly any two 

 of these vast sheets of water have had the same 

 origin. Recent quantitative measurement of 

 neighboring glaciation renders this agency a singu- 

 larly inconsequential factor. All things consid- 

 ered it is inferred that the rise and decline of these 

 great lacustral anomalies of the western arid 



