Chronometers, **6.5010.54 Clavius, C. Opera mathematica...(Continued 1.) et usus instrumenti horologiorum, - Horologiorum nove descriptio. 5. Romani calendarii & Gregorio XIII. restituti explicatio. - Novi calendarii Romani apologia adversus Michaelem Meestilinum, - Appendix in qua J, Scaliger, G. Germanus, & F. Viete confutantur, - Refutatio Cyclometride Scaligeri. Some of the treatises are independently paged; of (Continued)