70 J. B. Woodworth — Post- Glacial 



mineralogical constitution. The most perfectly symmetrical 

 pebbles are a variety of compact quartzite, or even vein quartz. 

 Finely crystallized granitic rocks also exhibit good facets, but 

 the quartz is apt to stand out above the feldspar. Quartz-por- 

 phyries, felsites and other massive rocks exhibit forms related 

 with original fragmental contour and mineralogic construction. 

 Pits are reamed out where minerals have decomposed, and 

 grooves are worn often regardless of structure but commonly 

 along lines determined by weakness in the rock. Facets 

 show no prevalent relations to joint-planes or bedding; but 

 often one can see that a joint-face has been cut and polished. 



The symmetry of the pebbles gives them an artificial 

 appearance in many instances. The original symmetry of 

 rounded water-worn pebbles has been preserved by the 

 production of balanced planes on opposite sides of the frag- 

 ment. Pyramidal, triangular pebbles are common. The 

 smaller pebbles by reason of the facility with which they may 

 be undermined and overturned by the wind, are more gene- 

 rally carved on all sides than the larger ones. 



Nomenclature. — In Germany sand-blasted pebbles receive 

 specific names depending upon the number of edges which 

 are developed by the intersection of facettes. The term 

 facetted-pebble proposed by Walther has already been given 

 in this country to a product of glacial action.* Since some 

 of the sand-carved pebbles are facetted, some grooved, and 

 others merely pitted, I would suggest that "glyptolith" 

 (glyptos, carved ; litkos, stone) might be employed, in the 

 sense of a rock surface carved by wind-blown sand. " Eolite " 

 has already been appropriated for a rock made by the deposi- 

 tion of sand by seolian action. f 



That the blowing of sand by wind must have been wide 

 spread in the interval between the disappearance of the last 

 ice-sheet and the occupation of the land by plants, is shown 

 by the fact that even now wind-blown sand and sand-blasting 

 is to be observed at numerous points on the sand-plains in this 

 district. The question is to determine whether the glyptoliths 

 found in grass-covered tracts or in wood-lands are due to a 

 phase of general deflation preceding the incoming of the 

 recent flora, and are, therefore, indicative of an eolian phase 

 succeeding the deglaciation of the district, or whether they 

 are due to secular wind erosion acting now and then as the 

 opportunity is offered by the removal of the soil and the ex- 

 posure of sand to the wind. My own observations have not 

 been sufficiently extended to come to a definite conclusion in 

 regard to this matter, particularly since in many places the 



*Chaniberlin: 7th Annual Report, U. S. a. S., p. 209, 1888. 

 fT. M. Reade: Geol. Mag., dec. ii, vol. ii, pp. 587, 588. 



