A mid 19th-century British source says auroras were a rare occurrence before the 18th-century. It quotes Halley as saying that before the aurora of 1716, no such phenomenon had been recorded for more than 80 years, and none of any consequence since 1574. It says no appearance is recorded in the "Transactions of the French Academy of Sciences" between 1666 and 1716. And that one aurora recorded in "Berlin Miscellany" for 1797 was called a very rare event. One observed in 1723 at Bologna was stated to be the first ever seen there. Celsius (1733) states the oldest residents of Uppsala thought the phenomenon a great rarity before 1716. The period between approximately 1645 to 1715 corresponds to the Maunder minimum in sunspot activity.