M. J. Delauney, from a study of Perrey’s tables of earthquakes from 1750–1842, found two groups of maxima each with a period of about twelve years, one commencing in 1759 and the other in 1756. Two other groups with twenty-eight year periods respectively commence in 1756 and 1773. These groups coincide with the times when Jupiter and Saturn reach the mean longitudes of 265° and 135°. From this Delauney concludes that earthquakes have a maximum when the planets are in the mean longitudes just mentioned. The increased number of earthquakes, especially in November, are attributed to the passage of the earth through swarms of meteors, and in like manner supposes the influence of Jupiter and Saturn to be due to their passing through meteor streams situated in mean longitudes 135° and 265°. As a consequence of this he predicts an increase of earthquakes in the years 1886, 1891, 1898, 1900, &c.[103] Dr. E. Naumann, who critically examined the large earthquakes of Japan, showed that there was an approximate coincidence between many of the disturbances and the thirty-three year period of meteoric showers.[104] Humboldt states that a great shower of meteors was seen at Quito before the great earthquake of Riobamba (Feb. 4, 1797). The earthquakes of 1766 and 1799 at Cumana are also said to have been accompanied with meteoric showers. Mallet gives a list of large earthquakes which occurred at the times when meteors were observed.[105] _The hours at which earthquakes are most frequent._—From the examination of a catalogue of over 2,000 earthquakes which occurred in various parts of the world between the years 1850 and 1857, made by Kluge, it is found that both for the northern and southern hemispheres the observations which were made during the night generally exceed those which were made during the day. +---------------------------+-----------------------+ | | Number of Earthquakes | +---------------------------+-----------------------+ | | Day | Night | |In the Northern Hemisphere | 938 | 1592 | |In the Southern Hemisphere | 292 | 357 | +---------------------------+---------+-------------+