Transactions. 47 



disdained to simplify their plan in order to save all this formid- 

 able labour, and seem to have only omitted any part of it when 

 the lie of the country was such as to provide the required defence 

 without artificial aid. It is certain, therefore, that every portion 

 of the work was deemed by its makers essential ; and though it 

 may be difficult for us now to understand its motive, that must 

 have been perfectly clear at the time. 



It will be seen by the sketch that whilst the stone wall, or 

 murus, runs along the northern boundary, with only a fosse in 

 front of it, to make it more difficult to surmount by an enemy 

 approaching from the north, there is quite an extensive system of 

 earthworks behind the murus — that is, on the southern side of it. 

 Those, known as the vallum, comprehend two distinct earth 

 mounds, or aggers, with a fosse between. Generally speaking, 

 this vallum follows the line of the murus, always, however, 

 leaving a space between broad enough to be traversed by a body 

 of troops. But that is not the case throughout the whole length 

 of the wall. A most notable feature of the work is that some 

 miles west of Chesters, where the high ridges of the country 

 begin, the murus follows the crest of this ridge throughout, and 

 does not leave it till the country drops down into the valley of 

 the Irthing at Gillsland. This line of elevated country forms an 

 irregular curve, the convex side being towards the north. The 

 vallum, however, does not keep to the heights. It proceeds in a 

 straight line across the country, leaving the high ground to the 

 north, and forms a string to the bow, joining the line of the murus 

 again just before it drops down suddenly nearly opposite to Green- 

 head railway station. 



This is a very remarkable feature of the wall, and its signifi- 

 cance is increased by the fact that about the place where the 

 vallum is farthest apart from the murus, a Roman station otcurs 

 on the line of the vallum, which has evidently no connection with 

 the series of stations on the Ime of the murus. This station, near 

 to Bardon Mill, known as Chesterholm, has been identified with 

 Vindolana. It lies on the edge of a depression, and high above it 

 is the line of the wall, proceeding westward from the great station 

 of Borcovicus, or Housesteads. The divergence of the vallum 

 from the high line of the murus across this stretch of country 

 lends itself to two explanations. Dr Bruce and those who hold 

 with him that the work was all made at the same time — the val- 



