The mountainous western coast of North and South America, or the shore of the Cordilleras, and the eastern coast of Asia stretching into the East Indies form the area of greatest earthquake activity, with 80 per cent of the entire mechanical force released in earthquakes concentrated there. Another area stretches from the Mediterranean toward the highland of Asia.
In an attempt to find the relation of earthquakes to other natural phenomena, a statistical investigation of the earthquakes of the middle of the nineteenth century was conducted, and the results suggested that earthquakes are more numerous when the moon is new and again when it is full, or when the pull of the moon acts in the same direction as the pull of the sun or when it acts in the opposite direction. The time when the moon is in perigee, or closest to the earth, was also found to be favorable for earthquakes.16 These observations were challenged as to their general validity.
However, mountain building is a process the causes of which have not been established; the migration of continents is but a hypothesis; and the crumbling of the earth's crust must have some additional cause besides the force of gravity, because this force was active when the crust was built and made possible the formation of the crust in its present shape. Hence, all these theories are only hypotheses about unknown causes of known phenomena.
On the basis of the material offered in the foregoing pages, the assumption is made here that earthquakes result from torsion of the 16 Cf. the scientific publications of A. Perrey.
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crust following a change in the position of the equator and the displacement of matter inside the globe caused by the direct attraction of a cosmic body when in a close contact. Pull, torsion, and displacement were responsible for mountain building, too.
If this conception of the causes of earthquakes is correct, then there must have been fewer and fewer earthquakes during the course of time since the last cosmic catastrophe. The regions of the Apennine Peninsula, the eastern Mediterranean, and Mesopotamia, for which we have reliable records, can be compared in this respect with the same regions of today.
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Earthquakes in Asia Minor, Greece, and Rome are described or mentioned by many classic authors. For the purpose of comparison with the earth-tremor activity of the present day, it is enough to point to fifty-seven earthquakes reported in Rome in a single year17 during the Punic wars (—217).
If our interpretation of the cause of earthquakes is correct, then not only must more tremors and stronger shocks have been experienced in olden times, but also their cause must have been known to the ancients.
Pliny wrote: 'The theory of the Babylonians deems that even earthquakes and fissures in the ground are caused by the force of the stars that is the cause of all other phenomena, but only by that of those three stars (planets) to which they assign thunderbolts."18
" Pliny ii. 86. i» Pliny u. 81.
CHAPTER 5
The Steeds of Mars
' I 'HE CASE of Abraham Rockenbach and David Herlicius, who * wrote about the year 1600, and who were informed on the matter of the comets of antiquity,1 shows that the contents of some old manuscripts were known to the scholarly world then, though not to modent scholars.
A scholar and pamphleteer, Jonathan Swift, in his Gulliver's Travels (1726), wrote that the planet Mars had two satellites, very small ones. "Certain astrologers . . . have likewise discovered two lesser stars, or satellites, which revolve about Mars, whereof the innermost is distant from the center of the primary planet exactly three of its diameters, and the outermost five; the former revolves in the space of ten hours, and the latter in twenty-one and a half . . . which evidently shews them to be governed by the same law of gravitation, that influences the other heavenly bodies."2
Actually Mars has two satellites, mere rocks, one being as small as about ten (?) miles in diameter, the other only five (?) miles.8 One travels around Mars in 7 hours 39 minutes, the other in 30 hours 18 minutes. Their distance from the center of Mars is even less than Swift said it was.4 They were discovered by Asaph Hall in 1877. With
1 See the Section, "The Comet of Typhon."
2 Travels into Several Remote Nations of the World, by Lemuel Gulliver (London, 1726), 11,43.
3 The diameters of these satellites are not exactly known (Russell, Dugan and Stewart, 1945).
4 Phobos is distant from the planet's surface less than one diameter of the planet (from the planet's center less than one and a half diameters of the planet).
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the optical instruments of the days of Swift, they could not have been seen, and neither Newton nor Halley, the contemporaries of Swift, nor William Herschel in the eighteenth or Leverrier in the nineteenth century suspected their existence.5 It was bold of Swift to assume their very short periods of revolution (months), measured only in hours; it was a very rare coincidence, indeed, if Swift invented these satellites, guessing correctly not only their existence, but also their number (two), and especially their very short revolutions. This passage of Swift aroused the literary critics' wonder.
It is an even chance that Swift invented the two satellites of Mars and thus by a rare accident came close to the truth. But it may also have been that Swift had read about the trabants in some text not known to us or to his contemporaries. The fact is that Homer knew about the "two steeds of Mars" that drew his chariot; Virgil also wrote about them.6
When Mars was very close to the earth, its two trabants were visible. They rushed in front of and around Mars; in the disturbances that took place, they probably snatched some of Mars'
atmosphere, dispersed as it was, and appeared with gleaming manes.7 The steeds were yoked when Mars (Ares) prepared to descend to the earth on a punitive expedition.
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When Asaph Hall discovered the satellites, he gave them the names of Phobos (Terror) and Deimos (Rout), the two steeds of Mars; 8 without fully realizing what he did, he gave the satellites the same names by which they were known to the ancients.
Whether or not Swift borrowed his knowledge of the existence of two trabants of Mars from some ancient astrological work, the ancient poets knew of the existence of the satellites of Mars.
6 Leverrier died one month after Asaph Hall made his discovery.
• Iliad xv. 119; Georgics iii. 91. Horses were sacrificed to Mars (Plutarch, Roman Questions, xcvii) either because they are animals employed in war, or because af the trabants of Mars which looked like horses drawing a chariot.
7 G. A. Atwater suggests that these might have been electrical effects.
8 Asaph Hall, The Satellites of Mars (1878): "Of the various names that have bemi proposed for these satellites, I have chosen those suggested by Mr. Madan of Eton, England," Deimos and Phobos.
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The Terrible Ones
Venus had a tail, considerably shortened since the time it was a comet, but still long enough to give the impression of a hanging flame, or smoke, or attached hair. When Mars clashed with Venus, asteroids,1 meteorites, and gases were torn from this trailing part, and began a semi-independent existence, some following the orbit of Mars, some other paths.
These swarms of meteorites with their gaseous appendages were newborn comets; flying in bands and taking various shapes, they made an uncanny impression. Those which followed Mars closely looked like a troop following their leader. They also ran along different orbits, grew quickly from small to giant size, and terrorized the peoples of the earth. And when, soon after the impact of Venus and Mars, Mars began to threaten the earth, the new comets, running very close to the earth, added to the terror, continually recalling the hour of peril.