Bode's Law, so-called, is only an empiric formula, but until the
discovery of Neptune it accorded so well with the distances of the
planets that astronomers were disposed to look upon it as really
representing some underlying principle of planetary distribution. They
were puzzled by the absence of a planet in the space between Mars and
Jupiter, where the ``law'' demanded that there should be one, and an
association of astronomers was formed to search for it. There was a
decided sensation when, in 1801, Piazzi, of Palermo, announced that he
had found a little planet which apparently occupied the place in the
system which belonged to the missing body. He named it Ceres, and it
was the first of the Asteroids. The next year Olbers, of Bremen, while
looking for Ceres with his telescope, stumbled upon another small
planet which he named Pallas. Immediately he was inspired with the
idea that these two planets were fragments of a larger one which had
formerly occupied the vacant place in the planetary ranks, and he
predicted that others would be found by searching in the neighborhood
of the intersection of the orbits of the two already discovered. This
bold prediction was brilliantly fulfilled by the finding of two more
-- Juno in 1804, and Vesta in 1807. Olbers would seem to have been led
to the invention of his hypothesis of a planetary explosion by the
faith which astronomers at that time had in Bode's Law. They appear to
have thought that several planets revolving in the gap where the
``law'' called for but one could only be accounted for upon the theory
that the original one had been broken up to form the several.
Gravitation demanded that the remnants of a planet blown to pieces, no
matter how their orbits might otherwise differ, should all return at
stated periods to the point where the explosion had occurred; hence
Olbers' prediction that any asteroids that might subsequently be
discovered would be found to have a common point of orbital
intersection. And curiously enough all of the first asteroids found