APPLICATION TO THE SYLYANIA SANDSTONE 651 



of the granules shows the imprints of the microscopic rhombohedrons of 

 the dolomite, thus proving that tlie enlargement of the original quartz 

 granules took place in situ. This phenomenon indicates that we have 

 had the principle of concentration, operating on either an aqueous or 

 ^olian type of granule^but which ? There's the rub ! — and there is so 

 much of it in evidence that a decision can be reached with reasonable 

 certainty. When not secondarily enlarged the Sylvania granules are 

 found to be all rounded, large and small, the rounding involving the real 

 bodies of the grains and not confined to the edges and corners (see fig- 

 ures 3, 4:^ 5, and 6, jolate 47). The surfaces of the coarser granules are 

 very characteristically frosted and pitted to an extent seen only in desert 

 sand. Indeed, this sand in its purity, degree of rounding, and assort- 

 ment has attained a degree of perfection that is being constantly ap- 

 proached, but never attained by any known modern example. It out- 

 Saharas the Sahara ! This perfected character of the Sylvania granules 

 can be understood when the probable history is known, a lengthy and 

 repeated buffeting with wind and wave, with no opportunity for the ac- 

 cession of new material and with a mineral substance inert to residual 

 action. The studies on the Escambia, Santa Eosa, and Palm Beach sands 

 of Florida indicate that the elimination of minerals other than crystal- 

 line quartz may be quite as perfect for aqueous sand as for aeolian (figure 

 4, plate 44), but that there is developed a plainly different type of 

 granule. 



Search must be made for field evidence, confirmatory or otherwise, of 

 the hypothesis of the aeolian origin of the Sylvania deposit. In the w^ay 

 of confirmation it may be said that there is an irregular stratification indi- 

 cated in all the exposures, the strata changing materially in thickness 

 within short distances; the cross-bedding is general and pronounced, the 

 steeper angles observed ranging from 28 to 32 degrees. In places the 

 cross-bedded layers, when followed downward, are seen to curve around 

 and become tangent to the stratification, mentioned by Barrell on page 

 642 of this 23aper, as characteristic of aeolian deposits. Steeply inclined, 

 oblique partings occur in the deposit, not conforming with the cross- 

 bedding nor the stratification^ which, may represent, so far as they are not 

 joints, the inclined surfaces of the dunes at various stages. Considerable 

 irregularity in the thickness of the formation is to be noted within short 

 distances. From the Ohio line northward into Michigan it grows thicker, 

 l)ecoming 288 feet thick at Milan, averaging in the Solvay wells at De- 

 troit 93.5 feet, then disappearing rather rapidly and being represented 

 by a silicious dolomite, from which the characteristic Sylvania granules 

 may be extracted by the use of acid. A similar dolomite is found in the 



