The Archaean rocks still solidly underlie the lowest depth he has ever reached.

The Mongolian or Great Altai, on the other hand, consists mainly of gneiss and Archaean rocks.

We part with our animals near a little shelter at the top of the Archaean rocks and scramble down a slippery trail.

As we have no recognisable remains of the animals and plants of the earliest age, we will not linger over the Archaean rocks.

Now, this is precisely what we find, The oldest rocks known to the geologist-theArchaean rocks-areoverwhelmingly volcanic, especially in their lower part.