A. A. Young — Sands of ' th J'ofsJ,/,,, S,i, t </. stone. 49 



Enclosures of another type are transparent spaces irregular 

 in shape; some of these of the form of six-sided j.ristns, ami 

 others appearing to be cylindrical. One of the latter, occurring 

 in a grain measuring '016 in. X '008 in., was -0045 in. X -0003 

 in. In another grain a tubular or prism-shaped cavity occurred 

 measuring -003 in. X '001 in., with an enclosed brown spot -001 

 in. long. A grain measuring -013 in. X "012 in. contained 

 eleven of these transparent cavities. 



Other enclosures are colored brown, yellowish, reddish, neu- 

 tral, or nearly black. Some are evidently cavities with colored 

 contents, a few with solid contents. One of the larger measured 

 •0045 in. X '0035 in. Some are of irregular contour, but the 

 most give hints of regular sides and forms. From one brown 

 enclosure, '0045 in. X '0033 in., there extended a tube, at right 

 angles, -003 in. long X "001 in. broad. In one grain, '024 in. 

 X .020 in., there was one brown cavity, -007 in. X "006 in., 

 with upper and lower sides parallel planes; a second similar 

 cavity, "003 in. x '002 in., in son; a a six-sided 



shape; a third cavity, drab colored, "002 in. X -001 in., and Eve 

 gonal. Such enclosures appear to 

 horizons of Potsdam, and are found to some 

 extent in St. Peter's. 



In two instances I have found inclusions that were apparently 

 minute grains of worn quartz. One was furnished by a nearly 

 oval grain of sand, measuring -03 in. X "025 in., whose crystal 

 envelope was very thin. Embedded in this grain, at a depth 

 of '005 in. from its upper surface, and nearly as much above 

 the under, lay a grain of worn quartz of rounded outline. It 

 measured '0045 in. X "0035 in. and was traversed by four par- 

 alell bands of cloudiness. The second instance occurred in a 

 grain nearly oval, '017 in. X '014 in. across. The enclosed grain 

 measured -0035 X '003 in. When viewed by reflected light it 

 was very distinct in outline: and translucent, but in a less 

 degree than the grain in which it was embedded. 



The quarried rock, that is composed of this crystal-sand, gleams 

 brilliantly in the sunlight. It may be worthy of record that 

 the same sparkle of minute crystals appears also in the smooth 

 surface of some of the fossil tracks, and in the ripple-marks. 

 many of which are preserved with admirable distinctness. 



The grain of sand figured above is one of special symmetry 

 and complete .. shows well the relation of the 



crystal envelope to the imprisoned nucleus with its inclusions. 

 Am. Jouk. Sci.-Third Sebies, Vol. XXIV, No. 139.— July, 1882. 



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