iv).
The Satpura range, thus defined, separates the valley of the Nerbudda from the valleys of the Tapti flowing west, and the Mahanadi flowing east.

The Vindhyan sandstones certainly are a formation of immense antiquity, perhaps pre-Silurian.

They are azoic, or devoid of fossils; and it is consequently impossible to determine exactly their geological age, or 'horizon' (ibid.p.

xxiii).

The cappings of basalt, in some cases with laterite superimposed, suggest many difficult problems, which will be briefly discussed in the notes to Chapters 14 and 17..