Originally these four ages were merely the four seasons; and as each season was under the supposed influence of a planet, it bore the name of the metal appropriated to that planet; thus spring was the age of the sun, or of gold; summer the age of the moon, or of silver; autumn the age of Venus, or of brass; and winter the age of Mars, or of iron.

Afterwards when astronomers invented the great year of 25 and 36 thousand common years, which had for its object the bringing back all the stars to one point of departure and a general conjunction, the ambiguity of the terms introduced a similar ambiguity of ideas; and the myriads of celestial signs and periods of duration which were thus measured were easily converted into so many revolutions of the sun.

Thus the different periods of creation which have been so great a source of difficulty and misapprehension to curious enquirers, were in reality nothing more than hypothetical calculations of astronomical periods.

In the same manner the creation of the world has been attributed to different seasons of the year, just as these different seasons have served for the fictitious period of these conjunctions; and of consequence has been adopted by different nations for the commencement of an ordinary year.

Among the Egyptians this period fell upon the summer solstice, which was the commencement of their year; and the departure of the spheres, according to their conjectures, fell in like manner upon the period when the sun enters cancer.