groups?

By the ancients. The phenomena of the heavens were studied in very
early ages by several nations of the East. The Chaldeans, the Indians,
the Chinese and the Egyptians have all left evidence of the industry
and ingenuity with which their observations were conducted.

_Phenomena_, appearances.

_Ingenuity_, skilfulness.


What progress did they make in Astronomy?

They built observatories,--invented instruments for observing and
measuring with correctness,--separated the stars into different groups
or constellations, for the more easily finding any particular
star,--gave particular names to most of the moving stars or planets,
and noted the periods which each took to move through its apparent
path in the heavens; and in many other ways the ancients helped to lay
the foundations of that mass of astronomical knowledge which men of
later ages have brought to more maturity.

_Constellation_, a cluster of fixed stars; an assemblage of
stars.

_Observatory_, a place so built as to command a view of the
heavens.