The Opera Mathematica of Christoph Clavius was compiled in 1611-1612 and contains works within the fields of both pure and applied mathematics. One of the most famous selections from this set is, of course, Clavius exposition of the Gregorian calendar. Except for the Commentary on Theodosius (1721) and the Commentary on John of Holywood’s Spheres (1784), however, there are no English translations of Clavius’ works. As Fr. MacDonnell wrote in 2001, “He was considered an illustrious mathematician and astronomer; one to whom scholars and potentates would entrust with the most sensitive scientific problems of the day. Even so, he has yet to be given full credit for all of his scientific accomplishments.” By making his work more accessible, this project is an attempt to give Christoph Clavius full credit.
To acquire and read the Opera Mathematica, first download “Complete Works of Christoph Clavius” (below). Second, uncompress the resulting .zip file, and finally, use your Web browser to open the index.html file. The result will be an HTML-based interface to Opera Mathematica.