INTERNAL STRTCTURE. •certainly accidental. Inattention to this circiim- ltance, has led feveral mineralogifts into error. I obferved a ftriking inftance of thefe rents in a quarry of gneifs, in the Foreft of Tharand, in Up per Saxony. The-gneifs, at firft fight, appeared to be difpofed in vertical ftrata, and as fuch it was viewed by De Luc : on a clofer examination, however, the apparent vertical; feams proved to be merely accidental parallel rents, perpendicular to the flaty ftru&ure of the ftone; therefore the ftrata were horizontal, not vertical. ; 1 5. Beds are always parallel with the ftrata ; thefe, therefore, point out the diredtion of the ftrata. 6. Although the flaty ftrudture points out to us the direction which the ftrata muft have, it does not follow, that a rock having a flaty ftrudure rs ftratified. j 7. In fandftone, Iimeftone, and rock-fait, regular and very extenfive ftripes are fometimes obferved, which have been confounded with true feams of ftratification. An attentive examination, however, always difcovers them traverfing the real ftrata feams. Von Buch, in his defcription of Landeck, and geognoftical obfervations made in Italy and Germany ; and Friesleben, in his obfervations on Thuringia, defcribe ftriking inftances of ftripes re sembling ftrata-feams. ; Strata
