A HISTORY OF DERBYSHIRE organization must necessarily vary widely from a fort one-tenth or even one-twentieth of the size, capable of holding a few hundred men. For our present purpose it is more important to consider the latter class, which, indeed, is far the better known to us through numerous excavations in many lands. It is a large class, and it is not surprising that its abundant examples show considerable differences. All of them are based on the same skeleton plan. All have the same general outline of a rectangle with rounded corners. But sizes and shapes fluctuate within wide limits. On the Rhenish and Danubian frontier the internal areas of the forts seem GREAT WALL r " ' TM^MHHM^H^HMaH^^MHMMri ^^^B ii--n mi a-tt IBM SCALE IN fICT 73 40 SO SO 100 ISO EAST GATE FlG. 4. HoUSESTEADS FoRT ON HADRIAN'S WALL, EXCAVATED IN 1898 BY MR. R. C. BoSANQUET. (I.-VI. and XIII.-XVIII. Barracks. VIII. Stores. X. Headquarters. IX.-XII. Probably officers' quarters.) in general to range between 4^ and 7 acres. But several are much smaller (i to 2 acres), and a few are distinctly larger. On the British frontier between Tyne and Solway, called Hadrian's Wall, the average size is smaller than in Germany. The areas range, for the most part, between 3 and 5^ acres, but one or two are smaller and several are larger. These fluctuations are partly due, perhaps, to accidents to the spacious- ness of the site, or the local abundance of stone or labour, or the views of a particular officer. But in the main they seem to correspond to the various sizes of the garrisons, that is, of the auxiliary regiments. A cohort or 'ala' might be either 500 or 1000 men ; a cohort was infantry, 196
