An account of Eustachio Divinis’s microscope was read at the Royal Society, in 1668.[12] It consisted of an object lens, a middle glass, and two eye glasses, which were plano convex lenses, and were placed so that they touched each other in the center of their convex surfaces; by which means the glass takes in more of an object, the field is larger, the extremities of it less curved, and the magnifying power greater. The tube, in which the glasses were inclosed, was as large as a man’s leg, and the eye glasses as broad as the palm of the hand. It had four several lengths; when shut up, it was sixteen inches long, and magnified the diameter of an object forty-one times; at the second length, ninety times; at the third length, one hundred and eleven times; at the fourth length, one hundred and forty-three times. It does not appear that E. Divinis varied the object lenses.
Philip Bonnani published an account of his two microscopes in 1698;[13] both were compound; the first was similar to that which Mr. Martin published as new, in his Micrographia Nova,[14] in 1742. His second was like the former, composed of three glasses, one for the eye, a middle glass, and an object lens; they were mounted in a cylindrical tube, which was placed in an horizontal position; behind the stage was a small tube, with a convex lens at each end; beyond this was a lamp; the whole capable of various adjustments, and regulated by a pinion and rack; the small tube was used to condense the light on the object, and spread it uniformly over it according to its nature, and the magnifying power that was used.
[13] Bonnani Observationes circa Viventia.
[14] Micrographia Nova, by B. Martin, 4to.
If the reader attentively consider the construction of the foregoing microscopes, and compare them with more modern ones, he will be led to think with me, that the compound microscope has received very little improvement since the time of Bonnani. Taken separately, the foregoing constructions are equal to some of the most famed modern microscopes. If their advantages be combined, they are far superior to that of M. Dellebarre, notwithstanding the pompous eulogium affixed thereto by Mess. De L’Academie Royale des Sciences.[15]