n Nubia the degradation of the oblong Egyptian
_mastaba_ gave rise to the simple stone circle. This type spread to the
west along the North African littoral, and also to the Eastern desert
and Palestine. At some subsequent time mariners from the Red Sea
introduced this practice into India.

[It is important to bear in mind that two other classes of stone circles
were invented. One of them was derived, not from the _mastaba_ itself,
but from the enclosing wall surrounding it (see my Ridgeway essay, Fig.
13, p. 531, and compare with Figs. 3 and 4, p. 510, for illustrations of
the transformed _mastaba_-type). This type of circle (enclosing a
dolmen) is found both in the Caucasus-Caspian area as well as in India.
A highly developed form of this encircling type of structure is seen in
the famous rails surrounding the Buddhist _stupas_ and _dagabas_. A
third and later form of circle, of which Stonehenge is an example, was
developed out of the much later New Empire Egyptian conception of
a temple.]

But at the same time, as in Nubia, and possibly in Libya, the _mastaba_
was being degraded into the first of the three main varieties of stone
circle, other, though less drastic, forms of simplification of the
_mastaba_ were taking place, possibly in Egypt itself, but certainly
upon the neighbouring Mediterranean coasts. In some respects the least
altered copies of the _mastaba_ are found in the so-called "giant's
graves" of Sardinia and the "horned cairns" of the British Isles. But
the real features of the Egyptian _serdab_, which was the essential
part, the nucleus so to speak, of the _mastaba_, are best preserved in
the so-called "holed dolmens" of the Levant, the Caucasus, and India.
[They also occur sporadically in the West, as in France and Britain.]

Such dolmens and more simplified forms are scattered in Palestine,[118]
but are seen to best advantage upon the Eastern Littoral of the Black
Sea, the Caucasus, and the neighbourhood of the Caspian. They are found
only in scattered localities between the Black and Caspian Seas. As de
Morgan has pointed out,[119] their distribution is explained by their
association with ancient gold and copper mines. They were the tombs of
immigrant mining colonies who had settled in these definite localities
to exploit these minerals.

Now the same types of dolmens, also associated with ancient mines,[120]
are found in India. There is some evidence to suggest that these
degraded types of Egy