An essay on visual glasses, (vulgarly called spectacles) wherein it is shewn ... that the common structure of those glasses is ... very prejudicial to the eyes; the nature of vision in the eye explained, and glasses of a new construction proposed / [Benjamin Martin].

  • Martin, Benjamin, 1705-1782.
Date:
1757
Catalogue details

Licence: Public Domain Mark

Credit: An essay on visual glasses, (vulgarly called spectacles) wherein it is shewn ... that the common structure of those glasses is ... very prejudicial to the eyes; the nature of vision in the eye explained, and glasses of a new construction proposed / [Benjamin Martin]. Source: Wellcome Collection.

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    For the U S E of the GENERAL APPARATUS 4 O F Optical Instruments. I. qpHE COMPOUND POCKET MICROSCOPE A muft be held in a perpendicular Manner, and the Objedf to be viewed is to be laid on the concave Glafs below, and then the inner Part moved gently up or down, will exhibit a clear and pleafant view of the Qbjedt ; if it be a tranfparent Object, the Light will be remedied from the Looking-Glafs below, and fhew it very plainly. A Tadpole, or fmall Fifh, is to be placed in the glafs Tube for viewing the Circulation of the Blood in the Tail, Fins, &c. Very fmall living Objedts are to be put into the fmalleft Tube to be viewed ; or they may be placed in the Concave with a Piece of plain Glafs over them to confine, yet not bruife, them. In the fame Glafs you alfo put a Drop or two of Water, Vinegar, &c. to view the Animalcules in them. For viewing the larger Sort of fmall Objedls you fcrew off the upper Part of the Mi- crofcope, and holding the Qbjedf juft under it, or before it, they appear very diftindl and beautiful. Note, The Objects to be viewed Jhould always be held in the Suni or in D a