A fortunate and rather strange circumstance has both facilitated and given a degree of certainty to the information and ideas we are about to lay before our readers. The tombs of the men of the polished-stone epoch--their funeral monuments--have been thoroughly studied, described, and ransacked by archæologists and antiquarians, who for many years past have made them the subject of a multitude of publications and learned dissertations. In fact, these tombs are nothing but the _dolmens_, or the so-called _Celtic_ and _Druidical_ monuments; but they by no means belong, as has always been thought, to any historical period, that is, to the times of the Celts, for they go back to a much more remote antiquity--the pre-historic period of the polished-stone age. This explanatory _datum_ having been taken into account, we shall now study the _dolmens_ and other so-called _megalithic_ monuments--the grand relics of an epoch buried in the night of time; those colossal enigmas which impose upon our reason and excite to the very highest pitch the curiosity of men of science. _Dolmens_ are monuments composed of a great block or slab of rock, more or less flat in their shape according to the country in which they are situate, placed horizontally on a certain number of stones which are reared up perpendicularly to serve as its supports. [Illustration: Fig. 130.--Danish _Dolmen_.] This kind of sepulchral chamber was usually covered by earth, which formed a hillock over it. But in the course of time this earth often disappeared, leaving nothing but the naked stones of the sepulchral monument. [Illustration: Fig. 131.--_Dolmen_ at Assier.] These are the bare stones which have been taken for _stone altars_, being referred to the religious worship of the Gauls. The supposed Druidical altars are, in fact, nothing but ruined _dolmens_. The purpose, therefore, for which they were elevated was not, as has always been stated, to serve as the scene of the sacrifices of a cruel religion; for, at the present day, it is completely proved that the _dolmens_ were the tombs of a pre-historic epoch. These tombs were intended to receive several dead bodies. The corpses were placed in the chamber which was formed by the upper slab and the supports. Some of these chambers had two stages or stories, and then furnished a larger number of sepulchres. Figs. 132 and 133 represent different _dolmens_ which still exist in France. [Illustration: Fig. 132.--_Dolmen_ at Connéré (Marne).] [Illustration: Fig. 133.--Vertical Section of the _Dolmen_ of Locmariaker, in Brittany. In the Museum of Saint-Germain.] Some _dolmens_ are completely open to view, like that represented in fig. 132, nothing impeding a perfect sight of them; others, on the contrary, are covered with a hillock of earth, the dimensions of which vary according to the size of the monument itself.