Volltext Seite (XML)
j Agate. a proper direction, we can always obferve the open ing by which the folution has entered*. Ribbon agate is formed in veins, and has been formed by depofition from different folutions. The mode of formation of breccia or fragment a gate is different from that of either of the preceding, if a completely formed agate vein is (again) rent, it is eafily conceivable, from the great brittlenefs of the ftcne of which it is compofed, that many pieces would break off, and fall into the numerous openings thus formed. A new folution being poured into thefe rents would fill them up, and connedt together all rhe fragments, and thus a brecciated agate would be formed. In a fimilar manner are formed the fmaller and greater angular lengthened drufy cavities of quartz a nd amethyft, that occur in agate. Similar rents, but on a fmaller fcale, are to be ob- 'ferved in ribbon agate, and thefe are generally filled ^ith quartz and ameihylt. * Many objections bave been oppofed to tbis explanation, but the only one worthy of notice is the following. If the cavities have been filled by infiltration, it is demanded, how can we ex plain the efcape of the water after the depofition of the ftony tnatter ? To this it may be anfwered, that as foon as the dilfolv- ed matttr was depofited, the water which held it in folution, from its lefs fpccific gravity, would be difplaced by' the heavier Pew folution, and efcape by the infiltration opening. Bb Gccgmstic