are attached to a cup.

These objects were observed to go through a series of periodic changes.
After having become invisible, they reappeared as two luminous straight
bands, projecting from each side of the planet; during the next seven or
eight years they gradually opened out, and assumed a crescentic form;
they afterwards began to contract, and on the expiration of a similar
period, during which time they gradually decreased in size, they again
became invisible. It was perceived that the appendages completed a cycle
of their changes in about fifteen years.

In 1656, Huygens, with a telescope constructed by himself, was enabled
to solve the enigma which for so many years baffled the efforts of the
ablest astronomers. He announced his discovery in the form of a Latin
cryptograph which, when deciphered, read as follows:--

'Annulo cingitur, tenui plano, nusquam cohaerente, ad eclipticam
inclinatio.'

'The planet is surrounded by a slender flat ring everywhere distinct
from its surface, and inclined to the ecliptic.'

Huygens perceived the shadow of the ring thrown on the planet, and was
able to account in a satisfactory manner for all the phenomena observed
in connection with its variable appearance.

The true form of the ring is circular, but by us it is seen
foreshortened; consequently, when the Earth is above or below its plane,
it appears of an elliptical shape. When the position of the planet is
such that the plane of the ring passes through the Sun, the edge of the
ring only is illumined, and then it becomes invisible for a short
period. In the same manner, when the plane of the ring passes through
the Earth, the illumined edge of the ring is not of sufficient magnitude
to appear visible, but as the enlightened side of the plane becomes more
inclined towards the Earth, the ring comes again into view. When the
plane of the ring passes between the Earth and the Sun, the unillumined
side of the ring is turned towards the Earth, and during the time it
remains in this position it is invisible.

Huygens discovered the sixth satellite of Saturn (Titan), and also the
Great Nebula in Orion.

JOHANN HEVELIUS, a celebrated Prussian astronomer, was born at Dantzig
in 1611, and died in that city in 1687. He was a man of wealth, and
erected an observatory at his residence, where, for a period of forty
years, he carried out a series of astronomical observations.

He constructed a chart of the stars, and in order to co