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Eyepiece, Diagonal. (i) An eyepiece fitted with a prism to 

 enable the observer to view, at right angles to the axis of 

 the optical instrument, the object. (2) An eyepiece in 

 which a very small portion of the sun's light is reflected 

 from the first surface of a wedge-shaped prism, the rest 

 being transmitted. [2, 3, 6, 9, 10, 11, 13, 15, 17, 18, 20, 21, 

 24, 25, 26, 27.} 



Eyepiece, Ehrlich. A microscope eyepiece with a variable 

 diaphragm, for estimating the number of red and white 

 corpuscles in the blood. [2, 3, 22, 26.] 



Eyepiece, Erecting. The form of eyepiece used in telescopes 

 and microscopes for giving an upright image of the object 

 observed. (7, 2, 3, 8, 9, 10, 11, 13, 15, 16, 17, 18, 21, 22, 23, 

 24, 27.] 



Eyepiece, Huyghenian. A negative eyepiece, designed by 

 Huyghens, for a microscope or telescope. It consists of two 

 plano-convex lenses separated by a considerable space, 

 with both curves turned away from the eye and towards 

 the incidental light. The focal lengths of the field and eye 

 lenses are in the ratio 3:1, while the distance between 

 them is numerically equal to twice the focal length of the 

 eyelens. [2, 3, 17, 18, 20, 21, 22, 23, 26, 27.] 



Eyepiece Indicator. A pointer mounted in a microscope eye- 

 piece. [2, 3, 20, 22, 26.] 



Eyepiece, Kellner. An eyepiece giving a very wide field of view. 

 It consists of a cemented pair of achromatic lenses and a 

 double convex lens. The field and eye lenses are of equal 

 focal lengths, and are separated by a distance numerically 

 equal to the focal length of either. [2, 3, 10, 20, 22, 23, 

 26. 27] 



Eyepiece Lenses. Simple or compound lenses used at the eye 

 end of telescopes, etc. [1, 2, 3, 6, 8, 9, 10, 11, 12, 14, 15, 

 17, 18, 20. 21, 22, 23, 24, 25, 26, 27.] 



Eyepiece Micrometer. A graduated scale usually placed in the 

 focus of the eyelens of an eyepiece. The graduated scale is 

 often replaced by one or more cobwebs or lines moved by a 

 micrometer screw. \2, 3, 10, 11, 14, 18, 19, 20, 21, 22, 25, 

 26, 27] 



Eyepiece, Monocentric. A concentric eyepiece. [2, 3] 



Eyepiece, Negative. An eyepiece incapable of giving a positive 

 image, i.e., the image due to the objective is formed on the 

 negative side of the field lens. [1, 2, 3, 8, 10, 11, 17, 20, 21, 

 23, 25, 26, 27.] 



Eyepiece, Pancratic. An erecting eyepiece of which the power 

 can be varied by altering the position of the lenses. 



Eyepiece, Positive. An eyepiece giving a positive image. 



Eyepiece, Ramsden. A positive eyepiece, designed by Ramsden, 

 consisting of two plano-convex lenses of the same kind of 

 glass,' but with their curved faces turned towards each other. 

 The two lenses are of equal focal lengths and separated by 



