. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. 168 PRACTICAL TKEATISE ON THE MICROSCOPE. ciety of Arts. The eye-piece in question was invented by Huyghens for telescopes, with no other view than that of diminishing the spherical aberration by producing the refrac- tions at two glasses instead of one, and of increasing the field of view. It consists of two planoconvex lenses, with their plane sides towards the eye, and placed at a distance apart equal to half the
. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. 168 PRACTICAL TKEATISE ON THE MICROSCOPE. ciety of Arts. The eye-piece in question was invented by Huyghens for telescopes, with no other view than that of diminishing the spherical aberration by producing the refrac- tions at two glasses instead of one, and of increasing the field of view. It consists of two planoconvex lenses, with their plane sides towards the eye, and placed at a distance apart equal to half the sum of their focal lengths, with a stop or diaphragm placed midway between the lenses. Huyghens was not aware of the value of his eye-piece; it was reserved for Boscovich to point out that he had, by this important arrangement, accidentally corrected a great part of the chro- matic aberration. Let fig. 118 represent the Huyghenian eye-piece of a microscope, F F being the field-glass, and E E the eye-glass, and L M N the two extreme rays of each of the three pencils, emanating firom the centre and ends of the ob- ject, of which, but for the field-glass, a series of co- loured images would be formed from B, R to B B; those near B. R being red, those near B B blue, and the intermediate ones green, yeUow, and so on, corre- sponding with the colours of the prismatic spectrum.— This order of colours, it will be observed, is the reverse j-j J18 of that occurring in the com- mon compound microscope, represented by fig. 115, in which the single object-glass pro- jects the red image beyond the blue. The effect just described, of projecting the blue image beyond the red, is purposely produced, for reasons presently to be given, and is called over-correcting the object-glass as to colour. It is to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly
Size: 1235px × 2023px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
