28 ANCIENT FORTIFICATIONS in 



ally regaining a country in which they found the recent works 

 of a polilhed people, they could not fail to acquire much know- 

 ledge in the arts. At the time, therefore, when Adrian built 

 his rampart, A. D. 120, we know, almoft to a certainty, that 

 the inhabitants of Scotland, as far to the north as the Grampi- 

 an mountains, underftood and practifed the art of constructing 

 durable buildings with mortar. The forts or caflella erecled 

 by Agricola, which Tacitus* fays were fo ftrongly con- 

 tracted as to refill: the utmoft efforts of the enemy to take 

 them by ftorm, were now in the pofTefnon of the Caledonians. 

 The Roman caflella were circular, and fometimes fquare, inclo- 

 fures, furrounded with a ftrong wall of ftone, hewn into 

 fquare blocks, and cemented with mortar. The fpace inclofed 

 was fufficient to contain various buildings likewife of ftone, 

 barracks for the winter habitation of the troops, granaries for 

 provifions, and fometimes baths. The form of thefe caflella 

 may be feen in the fculptures upon the Trajan column, and 

 their conftruction may be learnt from Vegetius. The re- 

 mains of a bath belonging to one of thefe caftella, probably 

 erecled by Agricola, were difcovered, within thefe few years,, 

 at the village of Dalnoter, between Glafgow and Dumbarton. 

 The Caledonians had witneffed the building of thofe Structures, 

 which were reared with the mofl perfect fkill in military archi- 

 tecture, from materials which the country furnifhed in abun- 

 dance. They were now in pofTeffion of the Structures them- 

 felves. It is reafonable, therefore, to conclude, that they now 

 learnt the art of constructing regular buildings with ftone and 

 mortar, and practifed it, both for the purpofes of defence and 

 habitation ; becaufe the contrary fuppofition would do violence 

 to all probability. 



The wall of Adrian, which was built in 120, and that of 

 Antoninus Pius, built> as Horsley thinks, in 140, were 



both 



* Vit. Agric. cap. 22. 



