astronomers for the last fifty years. He saw that the ring
was an object of astonishing interest, unique at that time, as it is,
indeed, unique still. He felt, however, that he had hardly demonstrated
the matter with all the certainty which it merited, and which he thought
that by further attention he could secure. Yet he was loath to hazard
the loss of his discovery by an undue postponement of its announcement,
lest some other astronomer might intervene. How, then, was he to secure
his priority if the discovery should turn out correct, and at the same
time be enabled to perfect it at his leisure? He adopted the course,
usual at the time, of making his first announcement in cipher, and
accordingly, on March 5th, 1656, he published a tract, which contained
the following proposition:--

aaaaaaa ccccc d eeeee g h
iiiiiii llll mm nnnnnnnnn
oooo pp q rr s ttttt uuuuu

Perhaps some of those curious persons whose successors now devote so
much labour to double acrostics may have pondered on this renowned
cryptograph, and even attempted to decipher it. But even if such
attempts were made, we do not learn that they were successful. A few
years of further study were thus secured to Huyghens. He tested his
theory in every way that he could devise, and he found it verified in
every detail. He therefore thought that it was needless for him any
longer to conceal from the world his great discovery, and accordingly in
the year 1659--about three years after the appearance of his
cryptograph--he announced the interpretation of it. By restoring the
letters to their original arrangement the discovery was enunciated in
the following words:--"_Annulo cingitur_, _tenui_, _plano_, _nusquam
cohaerente_, _ad eclipticam inclinato_," which may be translated into the
statement:--"The planet is surrounded by a slender flat ring everywhere
distinct from its surface, and inclined to the elliptic."

Huyghens was not content with merely demonstrating how fully this
assumption explained all the observed phenomena. He submitted it to the
further and most delicate test which can be applied to any astronomical
theory. He attempted by its aid to make a prediction the fulfilment of
which would necessarily give his theory the seal of certainty. From his
calculations he saw that the planet would appear circular about July or
August in 1671. This anticipation was practically verified, for the ring
was seen to van