Microscopium polydynamicum : or, a new construction of a microscope, wherein a variety of magnifying powers is communicated to each object-lens / [Benjamin Martin].

Benjamin Martin

Date:: 1771

Credit: Microscopium polydynamicum : or, a new construction of a microscope, wherein a variety of magnifying powers is communicated to each object-lens / [Benjamin Martin]. Source: Wellcome Collection.

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$Dfances from the fame Lens, will have an Image form'd by ity confanily variable in its Difance and Dimenfons, and this conftitutes the variable Magnifying Power of the Lens £ and to know what this is, in any particularCafe, you have the following Rule refulting from the fame Theorems, viz. From the given Difance of the Image from the Lensy fubdudl the focal Difance ; and the Remainder divided by the faid focal Difance, will quote the Number of Times the Image is bigger than the Qbjeff? which is the Magnifying Power in that Cafe. For Example; let the Magnifying Power be required when the Image is at the Diftance of 3 Inches from a Lens, whofe focal Diftance is \ of an Inch; by the foregoing o_7 C Rule we have —-112 = 3 ; or the Obje£I is magni¬ fied 3 Times in Length and Breadth. If the Eye-Glafs be of one Inch focal Diftance, it will fhew the Image 8 Times larger than it would be feen at the Diftance of 8 Inches, by the naked Eye; therefore 8x3 = 24, or the whole Power of magnifying in that Cafe, is 24 Times. Again fuppofe the Diftance of the Image from the ■fame Lens be 4 Inches; then, per Rule, ———■ - =4,3’; °>75 therefore 8 x453 = 34j4 the magnifying Power in this Cafe. Laftly; let the Diftance from the Lens be 5 Inches, then -—^ = 5>66 ; and 5,66x8—45,3 which is the 0,75 whole Magnifying Power at the given Diftance of 5 In¬ ches. And thus you proceed for any other Lens, and Diftance of the Image from it. Hence it is evident, that, in order to give a Variety of Magnifying] Powers to the fame Microfcopic Lens, no¬ thing more is neceflary than fuch a Conftrudtion of the B 2 Micro-$