To this second essay I have added an appendix, the chief aim of which is to give the sources at which the original manuscripts written by Newton and Leibniz when they were discovering their respective calculuses may be found. This has not been done hitherto, and it is all the more necessary that it should be done, as modern authors, such as Moritz Cantor in his monumental Vorlesungen zcher Ge schichte a'er Mathemati/e, neglect the fact that any early manuscripts Of Newton's on ?uxions are extant.