Bailey Willis was the second major American geologist to undertake reconnaissance research in China--in the years 1903-04. Together with the stratigrapher Eliot Blackwelder, topographer Harvey Sargent, and guide Li Shan, he travelled first in Shandong Province, then from Peking to Xian, thence across the mountains into Sichuan, and then by river via the Yangzi Gorges to Shanghai. It was hoped that they would discover the primeval ancestor of trilobites in China, but the search proved unsuccessful. Willis's stratigraphic findings are described, (...) as are his structural interpretations of what he observed in China. His work in China gave rise to some unfounded speculations about the possible causes of lateral Earth movements, due to rocks of different densities being adjacent to one another in the Earth's crust. These ideas were followed by several other 'theories of the Earth' during Willis's later career, some of which were also probably related to his experiences in China. He seemingly practised the formulation of 'multiple working hypotheses'. The paper also discusses the influence of Willis's survey and stratigraphic work on the subsequent development of Chinese geology, with particular attention given to the various meanings of the term 'Sinian System'. Mention is made of later work in China on Lower Cambrian stratigraphy. (shrink)