etween the eastern
boundaries of India which were known to Ptolemy and Marinus, and those our
newly discovered western parts of the coast of Africa and the Azores and
Cape Verd islands, the most westerly which were yet known. _Thirdly_, he
concluded that this still unknown space, between the eastern limits known
to Marinus and the Cape Verds, could not exceed a third part of the
circumference of the globe; since Marinus had already described 15 hours
towards the east, out of the 24 parts or hours into which the
circumference of the world is divided by the diurnal course of the sun;
and therefore to return in an easterly direction to the Cape Verd islands
from the limits discovered by Marinus, or to proceed westerly from these
islands to meet the eastern limits of Marinus, required only to pass over
about 8 parts in 24 of the circumference of the earth[1].

He reckoned, _fourthly_, that as the cosmography of Marinus had given an
account of fifteen hours or parts of the circumference of the globe
eastwards, and had not yet attained to a knowledge of the eastern
extremity of the land, it followed of course that this eastern extremity
must be considerably beyond those known limits; and consequently, that the
farther it extended eastwards, so much the nearer it must approach to the
Cape Verd islands, or the then known western limits of the globe: And, if
this space were sea, it might be easily sailed over in a short time; and
if land, that it would be much sooner discovered by sailing to the west,
since it must be much nearer to these islands in that direction. To this
may be added what is related by Strabo in his Fifteenth Book, that no army
ever penetrated to the eastern bounds of India, which according to Ctesias
is as extensive as all the rest of Asia. Onesicritus affirms that India is
a full third part of the world; and Nearchus says that it is four months
journey in a straight line from west to east. Pliny, in the 17th Chap, of
his 6th Book, says that India is a third part of the earth, and that
consequently it must be nearer Spain in the western than in the eastern
direction.

The fifth argument which induced the admiral to believe that the distance
in a western direction to India was small, was taken from the opinion of
Alfragranus and his followers, who computed the circumference of the
globe as much less than all other cosmographical writers, as they only
allowed 56-2/3 miles to a degree of longitude. Whence my fat