n 1864. In
this work Bertrand upheld the thesis that "the dolmens and _allees
couvertes_ are sepulchres; and their origin seems up to the present to
be northern." In 1865 appeared Bonstetten's famous _Essai sur les
dolmens_, in which he maintained that the dolmens were constructed by
one and the same people spreading over Europe from north to south. At
this time the dolmens of North Africa were still unstudied. In 1867
followed an important paper by Bertrand. In 1872 two events of
importance to the subject occurred, the publication of Fergusson's _Rude
Stone Monuments in All Countries_, and the discussion raised at the
Brussels Congress by General Faidherbe's paper on the dolmens of
Algeria. Faidherbe maintained the thesis that dolmens, whether in Europe
or Africa, were the work of a single people moving southward from the
Baltic Sea.

The question thus raised has been keenly debated since. At the
Stockholm Congress in 1874 de Mortillet advanced the theory that
megalithic monuments in different districts were due to different
peoples, and that what spread was the custom of building such structures
and not the builders themselves. This theory has been accepted by most
archaeologists, including Montelius, Salomon Reinach, Sophus Mueller,
Hoernes, and Dechelette. But while the rest believe the influences which
produced the megalithic monuments to have spread from east to west, i.e.
from Asia to Europe, Salomon Reinach holds the contrary view, which he
has supported in a remarkable paper called _Le Mirage Oriental_,
published in 1893.

The questions we have to discuss are, therefore, as follows: Are all the
megalithic monuments due to a single race or to several? If to a single
race, whence did that race come and in what direction did it move? If to
several, did the idea of building megalithic structures arise among the
several races independently, or did it spread from one to another?

We shall consider first the theory that the idea of megalithic building
was evolved among several races independently, i.e. that it was a phase
of culture through which they separately passed.

On the whole, this idea has not found favour among archaeologists. The
use of stone for building might have arisen in many places
independently. But megalithic architecture is something much more than
this. It is the use of great stones in certain definite and particular
ways. We have already examined what may be called the style of
megalithic ar