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the name Imaus to the eastern end of the system. In Ptolemy's geography the
name Imaus belongs to the central part from which the Ganges takes its rise. His
Emodus, a part of eastern Himalaya, begins from the sources of the Ganges and
stretches eastwards. But Ptolemy used the name Imaus not only for the part of
the principal system stretching from west to east, where the Ganges originates; he
gave it also to the tremendous meridional branch which goes out, at almost right
angles, from the latitudinal chain, and stretches far to the north, dividing the whole
northern half of Asia into Scythia intra Imaum Montem and Scythia extra Imaum
Montem. Some 60 or 70 years ago this meridional Imaus was supposed to include
the unfortunate Bolor-tag.

Both west and east of his meridional Imaus, Ptolemy has several other ranges,
the names of which he may have received at second or third hand through silk
traders from the country of the Seres, Serica, or which, perhaps, had been collected
already by Marinus. Vivien de Saint-Martin shows a certain resemblance between
Ptolemy and the Puranas; in both cases seven principal mountain ranges are men-
tioned, and some Puranas, just as Ptolemy, enumerate the rivers which take their
rise from each mountain-group.¹

There is quite a host of scholars who have wasted their brains and their ener-
gies in the hopeless and vain attempts to identify Ptolemy's geography with our
present detailed knowledge, and as a rule every new commentator puts forward his
own new system, different from those of his predecessors. Even scholars who have
attained the highest standard of knowledge, as LASSEN and RICHTHOFEN, have
yielded to this temptation. And, indeed, it would be both interesting and of great
value to know how far the information acquired by such men as Marinus and
Ptolemy reached towards the interior and the East of Asia. And still, Sir HENRY
YULE is right in pointing out the impossibility of such a task, of which also Bun-
bury says²: »The attempt of Lassen to identify the various places mentioned by
Ptolemy is based throughout upon the fundamental error of supposing that that
geographer possessed a map of India similar to our own, and that we have only
to compare the ancient and modern names in order to connect the two.»³

If, in the following pages, I appear to have committed the same error which I
am blaming in others, it is not so much any desire of mine to try and offer a new
explanation of a special question, as an attempt to show the enormous importance
of Ptolemy for the cartography of later times, and, in one special case, to prove
that the identification brought forward by some modern geographers cannot possibly
be correct. The problem I am referring to is the Tsangpo-Brahmaputra. But first
a few words should be said about the Indus and the Ganges as given by Ptolemy.