Micrographia nova: or, a new treatise on the microscope, and microscopic objects ... To which is added, an account of the camera obscura, and the solar microscope / [Benjamin Martin].

Benjamin Martin

Date:: 1742

Credit: Micrographia nova: or, a new treatise on the microscope, and microscopic objects ... To which is added, an account of the camera obscura, and the solar microscope / [Benjamin Martin]. Source: Wellcome Collection.

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$it appears; there is therefore a juft Degree of magnifying, more or lei's than which would be a Fault: So true is the Obfervation ot Horace, Eft Modus in Rebus \ funt certi denique Fines, £%uos ultra citraque ncquit confiflere ReStum. T h e r e are other Methods by which the magnifying Power- may be computed ; but this, here deliver’d, I take to be the eafi- eft of any mathematical one, and may be applied for any focal Length of the Objedt Lens. But if this be not underftood, the Reader will find a moft plain and pradtical Method of finding how much the Microfcope magnifies with any Objedt Lens what- foever, by the Micrometer only, at the End of the next Chapter, which he cannot fail to underftand or pradtife. CHAP. IV. Of the Micrometer, and its Ufe in mea- furing very finall Objects. THE Parts ot this Inftrument have been already deferibed, from whence its Ufe will be underftood in a very few Words. The Micrometer oq is fix’d in the Focus of the Eye-Glafs GH, and therefore its Point ^ will be clearly feen to move over the Parts of the Image, and to be, as it were, coincident with it. When any Objedt or Part thereof is to be meafured, the Point is to be fet very nicely to one Side thereof, while the Index q r points to- the Beginning of the Diviiions on the upper Part of the Plate, or Num¬ ber$