27 OCTOBER 1950, Page 13



SIR,—The Astronomer Royal had done me the honour of writing a review of Worlds in Collision (the Spectator, September 22nd). He des- cribes the contents of my book, and finds that the story of catastrophic events of global character " is supported by a wealth of quotation " from sources (thus leaving the theory of evolution to meet the chal- lenge), but opposes the thesis that celestial bodies (planets or comets) could have been the cause. He ably describes the catastrophe caused by a comet in the time of the Exodus and proceeds : " This comet is supposed to have collided with Mars in the time of Joshua in the year 747 B.C. and, as the result of the collision, to have become transformed into the planet Venus . . . . If a collision between Mars and Venus had occurred in the past . . . . then, starting from the present posi- tions and motions, and computing backwards, we should find that, at a certain epoch in past time, the positions of Mars and Venus were

identical . . . . It is found that no collision occurred • This is sufficient to disprove the main theme."

As to vestiges of past collisions or close contacts in the celestial sphere, I offer a few suggestions. However, to straighten things out, I should prefer to have in the quoted sentence, in conformity with my book, Isaiah instead of Joshua, and Earth instead of Venus (pp. 205 ff.). The last great perturbation I describe occurred on March 23rd, 687 B.C., between Mars and Earth, the last of a series of similar perturbations which started in the eighth century. Thus it would be futile to try to show by calculations from the present orbits of Venus and Mars the point of their encounter in the past. As to the vestiges of the close contacts between Mars and Earth in the past, which took place at fifteen-year intervals from 747 to 687, I pointed to the fifteen- year period between the close approaches of Mars and Earth at present (favourable oppositions) ; also to the similarity in the inclination of the axes of Earth and Mars, which has a meaning if magnetic fields played a role in these contacts.

I suggested also in Worlds in Collision that the atmosphere of Mars consists of neon and argon, and gave reasons for it ; or that Mars's polar caps have a chemical composition similar to that of the brilliant dust- clouds of Venus. This can be investigated by spectroscopic analysis.

The Astronomer Royal brings up a second argument : " A comet could never change into a planet . . . The mass of the largest comet is extremely small compared with that of any of the planets.' He says also that the mass of the comet is so small that the pressure of solar light drives out from the cometary mass the stream of minute particles which form its tail. To this I would answer that the pressure of light, ten thousand times weaker than the sun's attraction and acting here almost without the benefit of acceleration, cannot be ;made responsible for the velocities with which a cometary tail, as a rigid rod, makes its sweep in perihelio, subject to some strong repulsive force which drives the matter composing the tail away from thesun with enormously high velocities " in defiance of the .law of gravitation, nay, even of the recorded laws of motion " ( John F. Herschel).

And were not Jupiter, Saturn, Venus or Earth in the category of comets when they moved on elongated ellipses after having erupted from the sun, as the tidal theory assumes they did ?—Very sincerely


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