Before reviews devoted to particular branches of science had come into existence, results obtained by individual research were diffused by means of letters to those who were likely to be interested. At a later date they were published in encyclopaedic journals, in literary periodicals, and in the Proceedings of the various academies. This makes it extremely difficult to obtain accounts both accurate and complete of much that has been written in this or that particular subject. To assist in removing this difficulty, and to bring within the reach of the student the results of historical research, I have suggested, for instance, an examination of the periodicals, etc., which, while not exclusively devoted to science, may nevertheless contain material of the greatest value to us in the history of science. The suggestion had the honour of receiving the approval of one eminent bibliographer, and, in his turn, he did for three rare German periodicals what I had done for two of the most celebrated Italian literary journals.