The thesis is an introduction to the textbooks on international law written mainly in the 19th century. So the chief source' materials are the textbooks themselves. The study is not an exhaustive account of the work of each textbook writer, but only of his attempt to consider the law as a system. Nor does it cover every book written. Limitations of language mean that only books in French, German and English are included. Besides, the aim has been to give an impression of the general character of the textbooks, and it is felt that the omission of a number of works, especially in French and German, does not frustrate such a limited objective. (This means that Italy and Spain are neglected; the Italians are considered with Sereni's "The Italian Conception of International Law", and it is felt that Spain may be relatively unimportant pol itically in the 19th century). As the aim is to describe and explain the textbooks themselves, there is no attempt to write a general history of ideas. All secondary materials are subordinated to the task of explaining the textbooks. These materials are gleaned from general historical surveys which are to be found in the bibliography, there is some attempt to reconstruct university life, partly from modern surveys of legal education, and partly from legal journals and reviews of the time. However, this attempt was made with a view to explaining the books and questions which such research itself might raise were not pursued. The surveys, journals and reviews are set out in the bibliography.