The question whether the cromlech was originally covered by a cairn or mound has been the subject of much discussion, but its full consideration is outside the limits of this work. The great majority of existing cromlechs in Ireland are, now at least, of the free-standing order. Of these some, from the nature of their position and structure, could never have been the centres of tumuli. Others, no doubt, were covered; but, in the case of most, time has so altered their condition that it is now difficult to determine how they really stood in their original and finished state.[26] A little consideration will show that, as the cromlech and covered chamber belong to the same general class of sepulchral monuments, it was intended by the original builders that access should be had to them from without. Mr. Borlase, agreeing with Fergusson, is ‘inclined to regard the dolmens as no mere tombs intended to be closed for ever, but as sacred shrines in which the spirits of the dead were worshipped, and which were constructed with a view of being accessible to devotees.’[27] The remains deposited within had to be protected from the severity of the weather and the intrusion of wild animals. In the case of the uncovered cromlech all intervening spaces would be closed up with smaller stones and earth, and the walls banked up to the edge of the cap-stone. Mr. Borlase advances the theory that the cromlech, hitherto technically so-called, is the more megalithic portion of the giant’s grave, and ‘that both types, despite the difference in their appearance in the condition in which we now find them, belong to one and the same class of dolmen, originally of elongated form.’[28] He supports this by pointing out that the ‘giant’s grave’ is a long, wedge-shaped structure, rising gradually from a lower to a higher end, the latter having the heavier supports and larger covering stone. These would be the more difficult to destroy, for, in the long lapse of time, as stones were required for building or other purposes, the smaller and lighter would be carried away. How far this may be the case we cannot here consider; but some cromlechs, such as those raised of great boulder rocks, could never have been of the extended order of structure.