the Hermunduri, had more friendly dispositions towards the Romans than any other tribe had, and carried on lively commercial intercourse with them in the town of the Vindelici, Augusta; of the fact that this advance met with no resistance from them, we shall find traces further on. Under the following reigns of Hadrian, Pius, and Marcus, further progress was made with these military arrangements. [Sidenote: The upper Germanic Limes.] We cannot historically follow out the mode in which the frontier-fence between the Rhine and the Danube--still in great part subsisting as regards its foundations at the present day--came into existence, but we are able to recognise not merely the course which it took but also the purpose which it served. The work was as to its nature and purpose different in upper Germany from what it was in Raetia. The upper German frontier-fence, with a length in all of about 250 Roman miles (228 English miles[82]) begins immediately at the northern boundary of the province, embraces, as has been already said, the Taunus and the plain of the Main as far as the district of Friedberg, and turns thence southward to the Main, which it meets at Grosskrotzenburg above Hanau. Following the Main thence as far as Wörth, it here takes the direction of the Neckar, which it reaches somewhat below Wimpfen and does not again leave. Afterwards in front of the southern half of this frontier-line a second was laid out, which follows the Main by way of Wörth as far as Miltenberg, and thence is led for the most part in a straight direction to Lorch between Stuttgart and Aalen. Here to the upper German frontier-fence is joined on the Raetian, only 120 miles (108 English) long; it leaves the Danube at Kelheim above Ratisbon and runs thence, twice crossing the Altmuhl, in a curve westward likewise as far as Lorch. The upper Germanic Limes consists of a series of forts which are distant from each other, at the most, half a day's march (about nine English miles). Where the lines of connection between the forts are not closed by the Main or the Neckar, as stated above, there was introduced an artificial barrier, at first perhaps merely by a palisade,[83] afterwards by a continuous earthen rampart of moderate height, with a fosse outside and watch-towers built in at short intervals on the inner side.[84] The forts are not introduced into the rampart, but constructed immediately behind it at a distance seldom exceeding one-third of an English mile. [Sidenote: The Raetian Limes.]