236 MINERAL REPOSITORIES. a. When a number of veins, that do not interfedt one another, occur in the fame diftridt, it is ob- ferved that they have ufually the fame diredlion and conftituent parts ; thus intimating, that all of them have been formed at the fame time. When different venigenous depofitions occur in the fame diftridt, then the diredtion of the veins of thefe different depofitions is various, and they are arranged in fuch a manner, that each particu lar formation has a certain diredtion. b. Veins running in different diredtions, either crofs, or fimply meet one another. When they crofs, that which is croffed or interfedled is the oldeft, and that which croffes or interfedts, the newejl. This important obfervation was firft made on the continent of Europe by Werner, and in England by Price, in the mines of Cornwall. In confidering the relative age of veins, there is ano ther dillindlion to be attended to. It is founded on the materials of which the vein is compofed, and their greater or lefs incorporation with the rock which the vein trayerfes. The oldelt veins in a mountain are thofe compofed of nearly the fame materials as the flrata they traverfe, and in which no diftindt feam of feparation is to be obferved between their fides and walls; on the contrary, the fubftance of the vein is to be obferved mix ed with, and paffing into that of the rock ; and it wedges out in every direction in the mafs of jrock, thus fliewing, that it has not been filled from above
