"Dr. Gregory's elements of catoptrics and dioptrics. To which is added I. A method for finding the foci of all specula as well as lens's universally. As also for magnifying or lessening a given object by a given speculum or lens in any assign'd proportion, &c. II. A solution to those problems which are left undemonstrated. III. A particular account of microscopes and telescopes, from Mr. Huygens. With an introduction shewing the discoveries made by catoptrics and dioptrics." added to your shopping cart ×