The study of the dialects of modern Greek in the nineteenth century laboured under two difficulties, one of which has only partially been surmounted at the present day. The first was the absence of descriptive accounts of the speech of individual regions. Much has been done in more recent years to remedy this short coming, but much still remains to be done. There is still no linguistic atlas of Greece. There are still no descriptions of the dialect of many areas. And those which do exist are often based on antiquated principles, and take little account of modern linguistic science or of the advances that have been made in the study of the dialects of other European languages, particularly those of the Romance and Germanic families. The other shortcoming of earlier work in the field was the tendency to regard modern Greek dialects as the direct descendants of the dialects of ancient Greek. Scholars of the generation of F. W. Mullach sought to find Dorisms and Aeolisms in the medieval and modern Greek dialects, or even went further back, seeking the origin of certain of their characteristics in primitive Indo-European. We have seen that the ancient dialects were almost entirely replaced in late Hellenistic times by the Koine, the common Greek language based upon Attic.