Adams gives the Magi the classic two-principle Persian theology and runs their line forward to the Gaurs of her own day, the Zoroastrian survival the reservoir keeps returning to.
In Hannah Adams
In Adams’s own words, from the 1817 Dictionary. Each passage is quoted verbatim under its own entry.
Magi, interpreters of sacred mysteries. The Magi, or Magians, are an ancient Persian sect, who believed in two co-eternal principles, namely, Oromasdes, the source of all good, and Arimanius, the fountain of all evil. The former they worshipped under the symbol of its purest emblem, a perpetual fire.
Their priests attained to such extraordinary skill in philosophy, that some have imagined they exercised curious and diabolical arts, and hence arose the term Magicians. Such were the ancient Magi of the Persians; their descendants in Persia are the Gaurs of the present day.
Hannah Adams, A Dictionary of All Religions (Boston, 1817), entry “Magi.”