_Souterrains._--Within the inner rampart, but not in the raised mound as far as we have examined, underground passages and chambers varying in plan have been discovered. These earth-houses, to which the term _Souterrain_ is now usually applied, are generally similar in structure to the sepulchral chambers already described, the passages being lined and covered with stones, and the chambers of a bee-hive shape, formed by overlapping courses. Where the earth was sufficiently compact the excavation was sometimes made practically without the aid of stone, which was used only in forming the entrance. It is evident from the intricate nature of these underground structures, and the readiness with which they could be defended from attack, that they were designed as places of safety. They were probably used both as places of temporary retreat and as storehouses, the want of ventilation, save that derived from the narrow external entrance, rendering them unfit for continued habitation. Tacitus says the Germans dug underground dwellings: ‘These they use as winter retreats and granaries, for they preserve a moderate temperature; and upon an invasion, when the open country is plundered, these recesses remain inviolated, either because the enemy is ignorant of them, or because he will not trouble himself with the search.’ An examination of the kitchen-middens of some of these raths produced the ordinary ‘finds’ of primitive dwellings, stone, flint, and bone weapons and implements, the bones of animals used for food, fragments of pottery, bronze and iron objects. The Whitechurch rath, examined by Mr. R. J. Ussher, yielded a variety of these, including many iron objects, which showed that its occupation probably covered a long period of time. The rath had been deeply excavated to form the chambers and an extensive system of connecting galleries.[78] Souterrains are found apart from raths in isolated places in many parts of Ireland. They are very similar to those found in Scotland, where they are known as ‘eirde houses,’ ‘weems,’ or ‘Picts’ houses,’ and also to those found in Cornwall, which seems to point to a common origin for all. ‘The only slight difference between the Irish and the Scotch,’ says Dr. Munro, ‘is in the extent of curvature of the main gallery, which appears to be less pronounced in the Irish souterrains.’ He also points out that they differ in being so often found in connection with raths, as among the Scotch examples ‘only one instance is known inside a fort--viz., that in the ancient fort known as Macbeth’s Castle on Dunsinane Hill.’[79] Underground dwellings have been used by primitive races everywhere--in Asia, Africa, and America, as many travellers testify.