Before we pass on to the consideration of those _castra_ which, like Manchester and Lancaster, have preserved to the present day their original Roman or Celtic prefixes in more or less altered shapes, we must glance briefly at a general principle running through the modernised forms now in use. The reader, with his usual acuteness, will have noticed that the word Ceaster reappears under many separate disguises in the names of different modern towns. Sometimes it is _caster_, sometimes _chester_, sometimes _cester_, and sometimes even it gets worn down to a mere fugitive relic, as _ceter_ or _eter_. But these different corruptions do not occur irregularly up and down the country, one here and one there; they follow a distinct law and are due to certain definite underlying facts of race or language. Each set of names lies in a regular stratum; and the different strata succeed one another like waves over the face of England, from north-east to south-westward. In the extreme north and east, where the English or Anglian blood is purest, or is mixed only with Danes and Northmen to any large extent, such forms as Lancaster, Doncaster, Caistor, and Casterton abound. In the mixed midlands and the Saxon south, the sound softens into Chesterfield, Chester, Winchester, and Dorchester. In the inner midlands and the Severn vale, where the proportion of Celtic blood becomes much stronger, the termination grows still softer in Leicester, Bicester, Cirencester, Gloucester, and Worcester, while at the same time a marked tendency towards elision occurs; for these words are really pronounced as if written Lester, Bister, Cisseter, Gloster, and Wooster. Finally, on the very borders of Wales, and of that Damnonian country which was once known to our fathers as West Wales, we get the very abbreviated forms Wroxeter, Uttoxeter, and Exeter, of which the second is colloquially still further shortened into Uxeter. Sometimes these tracts approach very closely to one another, as on the banks of the Nene, where the two halves of the Roman Durobrivæ have become castor on one side of the river, and Chesterton on the other; but the line can be marked distinctly on the map, with a slight outward bulge, with as great regularity as the geological strata. It will be most convenient here, therefore, to begin with the _casters_, which have undergone the least amount of rubbing down, and from them to pass on regularly to the successively weaker forms in _chester_, _cester_, _ceter_, and _eter_.