These so-called secondary earthquakes, although in many instances they may be due to earth pulsations produced by earthquake, or to the immediate sensible shaking of a large earthquake, may perhaps, in certain instances, be attributed to some widespread disturbance beneath the crust of the earth. The occurrence of periods where all earthquake countries suffer, unusual disturbances indicate the probability of such underground phenomena. CHAPTER XIV. DISTRIBUTION OF EARTHQUAKES IN TIME (_continued_). The occurrence of earthquakes in relation to the position of the heavenly bodies—Earthquakes and the moon—Earthquakes and the sun; and the seasons; the months—Planets and meteors—Hours at which earthquakes are frequent—Earthquakes and sun spots—Earthquakes and the aurora. _The position of the heavenly bodies and the occurrence of earthquakes._—Since the earliest times, in searching for the cause of various natural phenomena, man has turned his energies towards the heavens. One of the earliest observations was the connection that exists between the season of the year and the motions of the heavenly bodies. Tides were seen to be influenced by the moon. In later times it has been discovered that periods of maximum magnetic disturbances occur every ten or eleven years with the sun spots, and Herr Kreil, of Vienna, tells us our satellite, the moon, has also an influence upon the magnet. From day to day we see the bond connecting our planet with the sun, the moon, and other heavenly bodies which are outside us gradually becoming closer. Inasmuch as many phenomena, like the motion of the tides, the rise and fall of the barometer, fluctuations in temperature, are all more or less directly connected with the relative position of our planet with regard to the sun and moon, any coincidence between the phases of these bodies and the occurrence of earthquakes more or less involves a time relationship with the other phenomena resultant on lunar and solar influences. _Earthquakes and the position of the moon._—Many earthquake investigators have attempted to show the connection between earthquakes and the phases of the moon. The first and most successful worker in this branch of seismology was Professor Alexis Perrey, of Dijon, who, after many years of arduous labour in tabulating and examining catalogues of earthquakes, showed that earthquakes were more likely to occur at the following periods than at others. 1. They are more frequent at new or full moon (syzygies) than at half moon (quadratures). 2. They are more frequent when the moon is nearest the earth (perigee) than when she is farthest off (apogee). 3. They are more frequent when the moon is on the meridian than when she is on the horizon.