This Prince paſſed by the impregnable City of Taitung; which as it is the laſt City towards the North, ſo alſo it is the Key and Bulwark of the Province of Xanſi againſt the irruption of the Weſtern Tartars; for it commands all the Souldiers which keep the many Fortifications of thoſe Quarters, where a fair Level down extending itſelf beyond that famous Wall, I mentioned heretofore, gives a fit occaſion for the incurſion of the Tartars.