28 Introductory Biology 



combined lenses when viewing objects and discovered that a second lens 

 would magnify the enlarged image from a magnifying glass. Their 

 microscope was made of three tubes, had a size of 2 by 18 inches, and 

 magnified about nine times. 



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 mm 



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Fig. 1. — Leeuwenhoek's microscope (1673). This simple microscope consisted 

 of a lens mounted between two flat pieces of metal, with an adjustable point for 

 holding the specimen and focusing purposes. (From the Evolution of the Micro- 

 scope, American Optical Company, Instrument Division.) 



Fig. 2. — Hooke's microscope (1665). The body tube contained a series of 

 lenses which magnified the image in the manner of a compound microscope. 

 Illumination was provided by a lamp and a bull's-eye condenser. The instrument 

 was sixteen inches high and had a maximum magnification of 42 x. (From the 

 Evolution of the Microscope, American Optical Company, Instrument Division.) 



Robert Hooke (1635-1703), an English microscopist, constructed an 

 outstanding microscope in 1665 which consisted of an objective lens, a 

 field lens, and an eye lens. The latter two magnified the image of the 



