A long time ago, I remember reading about a work that showed that there were no distinct breaks in the local dialects as one travelled from west to east across France, and how at the easternmost areas, the dialect shared more in common with German than it did with the westernmost dialects. Now, many years later, I am trying to track down some concrete references to anchor this memory. But I have had no luck! I vaguely have the notion that the study was a classic or well-known one in linguistics, but this, too, might be wrong ...
Can someone help out? Either by affirming this is true with pointers to references, or by firmly knocking me on the head and telling me that I am misremembering in my old age due to the misadventures of a misspent youth?
So, maybe I am even more confused and I meant a French-Italian gradient rather than French-German. In which case, Ferdinand de Saussere's "Course in General Linguistics", Part 4 ("Geographical Linguistics"), Chapter 3 ("“Causes of Geographical Diversity”), describes part of the phenomenon:
“Just as one cannot say where High German ends and Low German begins, so also it is impossible to establish a line of demarcation between German and Dutch, or between French and Italian. Taking points far enough apart, it is possible to say with certainty ‘French is spoken here; Italian is spoken there’. But in the intervening regions, the distinction becomes blurred. The notion of smaller, compact intermediate zones acting as linguistic areas of transition (for example, Provençal as a half-way house between French and Italian) is not realistic either. In any case, it is impossible to imagine in any shape or form a precise linguistic boundary dividing an area covered throughout by evenly differentiated dialects. Language boundaries, just like dialect boundaries, get lost in these transitions. Just as dialects are only arbitrary subdivisions of the entire surface covered by a language, so the boundaries held to separate two languages can only be conventional one”
So, it does talk about the blending of French into Italian, without any distinct breaks between dialects. But it does not describe not the easternmost French dialects being closer to westernmost Italian dialects rather than the westernmost French dialects, which was the other part of what I remembered.