nd contemporary
writers.

We are indebted to Cleomedes for most of what we know of his opinions and
discoveries; with such as relate to morals or to pure astronomy, we have no
concern. But he was of service also to geography. He measured an arc of the
terrestrial meridian; but his operation, as far as we can judge by the
details which have reached us, was far from exact, and of course his result
could not be accurate; it would appear, however, that his object was rather
to verify the ancient measures of the earth, particularly that of
Eratosthenes, and that he found them to agree nearly with his own. He
explained the ebbing and flowing of the sea, from the motion of the moon,
and seems to have been the first who observed the law of this phenomenon.
In order to represent the appearance of the heavens, Cicero informs us that
he constructed a kind of planetarium, by means of which he exhibited the
apparent motion of the sun, moon, and planets round the earth. It is on the
authority of Posidonius, that Strabo relates the voyage of Eudoxus of
Cyzicum from the Persian Gulf round Africa to Cadiz, which we have already
mentioned.

Having thus exhibited a view of the discoveries in geography, the advances
in the sciences connected with it, and the commercial enterprises of the
Egyptians, while under the dominion of the Ptolemies, it will be proper,
before beginning an account of the geographical knowledge and commercial
enterprises of the Romans (who, by their conquest of Egypt, may be said to
have absorbed all the geographical knowledge, as well as all the commerce
of the world, at that period), to recapitulate the extent of the Egyptian
geography and commerce, especially towards the east We shall direct our
retrospect to this quarter, because the commodities of the east being most
prized, it was the grand object of the sovereigns and merchants of Egypt,
to extend and facilitate the intercourse with that quarter of the globe as
much as possible. And we are induced to undertake the retrospect, because
the exact limit of the geographical knowledge and commercial enterprise of
the Ptolemies is differently fixed by different authors: some maintaining
that the Egyptians had a regular and extensive trade directly with India,
and of course, were well acquainted with the seas and coasts beyond the Red
Sea; while other authors maintain, that they never passed the straits of
Babelmandeb, and that even within the straits, their geographic