A general history of animalcules .... Being part I of 'A history of infusoria, living and fossil' / [Andrew Pritchard].

  • Andrew Pritchard
Date:
1843
Catalogue details

Licence: Public Domain Mark

Credit: A general history of animalcules .... Being part I of 'A history of infusoria, living and fossil' / [Andrew Pritchard]. Source: Wellcome Collection.

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    myself determined on presenting the public with detailed methods of constructing and testing achromatic micro¬ scopes. I further directed the attention of my workmen to the subject, and gave them, from time to time, such infor¬ mation, as, with their skill and perseverance, might advance them in this branch of art, and I believe, up to the present time, the only successful artists in this country are those who have been in my employ. In cases where an achromatic microscope cannot be procured, recourse should be had to single lenses or doublets, for the ordinary compound, however well con¬ structed, cannot be depended upon. With respect to the cost of an effective microscope, with a moderate equipment of apparatus, such for example as the one described in the 6th chap, of the Microscopic Illustrations, which is of the best construction I have seen, the price would now be from 20 to 30 guineas. As there are a great many persons who require only a plain, sound instrument, of more moderate cost, I have deemed it ex¬ pedient to take this also into consideration, and, after much api^lication and repeated experiments, have at length produced one, in every way suitable to the case. Such is my vertical tripod achromatic microscope. It may be stated that nine-tenths of the observations recorded in this work may be repeated and tested by this microscope. On comparing the above instruments with that used by Dr. Ehrenberg, there is no doulit that, in point of mecha¬ nical construction, they are greatly superior, whilst the optical part is equal to any with which his researches have been made. In adverting to this portion of my suliject, I am