 At this time, he published his famous "Notes on Southern Rus"' in which he pioneered a new Ukrainian orthography for the Ukrainian vernacular, the "Kulishivka" alphabet, based on phonetics rather than etymology.This later became the basis of the modern written Ukrainian language.In the 1860s and 1870s, he gradually turned more conservative and began to criticize Shevchenko, the Cossack revolts, and the ideal of the Cossacks as the defenders of popular liberty.