This second part of the sixth volume of Joseph Needham's great enterprise is the first to be written by a collaborator. Francesca Bray, working closely with Dr Needham, has produced the most comprehensive study of Chinese agriculture to be published in the West. From a huge mass of source material, often confusing and obscure, , and from first-hand study in China, she brings order and illumination to a crucial area of Chinese technological development. Miss Bray sees agriculture as a system of technology holding a balance between nature and society: it represents an interplay between what is allowed by the natural environment and what is hindered by the state of society. She thus begins her book with an account of the ecological background to China's agricultural history and with a thorough survey of the source material. The main body of the book is an account, organised broadly along the lines of the great medieval Chinese treatises, of the technological history of agriculture, with major sections devoted to field systems, implements and techniques (sowing, harvesting, storing) and crop systems (what has grown and where and how crops rotated). The crops studies in detail are those without which no Chinese could survive: cereals, legumes, oil crops, tubers, fibre crops, vegetables and fruit - the crops, in other words, of self sufficiency in times of hardship and of commercial enterprise in times of prosperity. The concluding section contrasts Europe's Agricultural Revolution with agrarian change in North China in the Han and with the 'Green Revolution' in South China in the Sung. Important distinctions between dry-grain and wet-rice agriculture are noted with the consequent variations in the development of Chinese society. In the theoretical analysis which concludes this section we find a vital contribution to the elucidation of the main question posed by Dr Needham's work: why did the Scientific Revolution which transformed the world take place in Europe and not in China?