Speyer Line (Isogloss)
The Speyer Line is also known as the Appel- / Apple Line and is usually viewed as the southern borderline of the Central German language area, which is bordered in the north by the Benrath Line . South of the Speyer line is the area of the Upper German dialects . Since the Speyer line crosses the Main several times in the cities of Faulbach , Freudenberg and Großheubach , it is also called the Main Line . There, in the Spessart region , it is also known regionally as the Äppeläquator .
The Speyer line began north of Pilsen and crossed the German-Czech border south of the city of Karlsbad . Until then, it has been obsolete since 1945, as the German-Bohemian dialects gave way to Czech with the expulsion of the German-speaking population . It now runs over the Ore and Elster Mountains and from there follows the Thuringian Forest to the Rhön (this roughly corresponds to the cities of Plauen - Rudolstadt - Arnstadt - Eisenach ).
At Vacha , the Germersheim line meets the Speyer line, which it follows to Gemünden , before separating from the Speyer line again there. Now the line runs along the western side of the Spessart and crosses the Main several times at the Mainviereck .
In Eberbach the isogloss to exceed Neckar and south of Speyer the Rhine. The Speyer and Germersheim lines meet again at Germersheim and now run together up the Rhine towards the German-French border. South of Karlsruhe , more precisely near Ettlingen , the Karlsruhe Line crosses the Rhine. It crosses the German-French border and meets the Speyer line near Weißenburg and the three bundles of isoglosses now end together in the Vosges .
The dialects south of the Speyer line, the Upper Germans, did the High German sound shift with the change from Appel to Apple to a greater extent than the dialects north of it, but this sound shift did not take hold completely. It was only carried out completely and consistently on the southern edge of the German-speaking area, in High Alemannic and Tyrolean .