His principal works are his edition of the Sachsenspiegel (in 3 vols., 1827, 3rd ed., 1861, containing also some other important sources of Saxon or Low German law), which is still unsurpassed in accuracy and sagacity of research, and his book on Die Hausand Hofmarken (1870), in which he has given a history of the use of trade-marks among all the Teutonic nations of Europe, and which is full of important elucidations of the history of law and also contains valuable contributions to the history of art and civilization.
An excellent harbour, sheltered against pirates, it became almost at once a competitor for the commerce of the Baltic. Its foundation coincided with the beginning of the advance of the Low German tribes of Flanders, Friesland and Westphalia along the southern shores of the Baltic - the second great emigration of the colonizing Saxon element.
The inhabitants are mainly of the Saxon stock and speak Low German dialects, except in the Upper Frankish district around Siegen, where the Hessian dialect is spoken.
To it Sundanese stands in the relation that Low German holds to High German, and the Madurese in the relation of a strongly individualized dialect.