The nearer together that these phenomena have occurred the stronger have they been.

Professor M. S. di Rossi brings forward many examples where there has been a coincidence between the appearance of the aurora and earthquakes. On 139 nights out of 211 days the aurora was seen in some parts of Italy, and ninety-three times earthquakes were felt. On forty-six occasions earthquakes and aurora took place together.[111] In considering the probability of a connection existing between these two phenomena, we must bear in mind that the aurora is at no great height above the surface of our earth, and, further, that it can be partially imitated. The fact that in earthquake countries, like Japan, the aurora is practically never seen, would indicate that we can neither regard this imperfectly understood phenomenon either as an effect or cause of earthquakes. That earthquakes and the appearance of the aurora in certain countries should not sometimes coincide is an impossibility.

Dr. Stukeley, who, it must be remembered, attempted to correlate the phenomena of earthquakes and electricity, when writing of the disturbances which shook England in 1849 and 1850, says that the weather had been unusually warm, the aurora borealis frequent and of unusually bright colours, whilst the whole year was remarkable for its fire-balls, lightnings, and corruscations.[112]

The aurora was observed before the commencement of the Maestricht earthquakes in 1751[113] whilst at the time of the shock flashes of light like lightning were observed in the sky.

Glimmering lights were seen in the sky before the New England earthquakes (Nov. 18, 1755), and again, before the disturbances which occurred in the same region in 1727, peculiar flashes of light were seen.

Preceding the Sicilian earthquake of 1692 strange lights were seen in the sky. Ignis fatui have also been observed with earthquakes. At the time of auroral displays Bertelli has observed microseismical disturbances, and M. S. di Rossi, who has made similar observations, thinks that there is an intimate connection between the aurora and earthquakes; the aurora either occurring in a period of earthquakes, or else taking the place of earthquakes.