OF THE FIELD OF THE MICROSCOPE. 



87 



actual areas for the case when die hemispherical surface is taken 

 as equal to 1,000,000 ; die fifth contains the corresponding tan- 

 gential area. 



10 



17 



_' 

 S3 



: 



:-.' 



r 



- 



- 



10 



- 



40 

 50 



1 



4 



1 



100 

 400 



IfM 



14102 

 37601 



38 

 Iff 

 Mi 



151&2 

 34074 



257215 



Mi 



3827 



15545 



35000 



MM 



108721 



166666 



710140 



1500000 



On comparing these calottes with the nearly corresponding 

 combined amplifications (t^., such as are practically obtainable), 

 the result we arrive at, as stated above, is a gradual diminution 

 of the amount of light for the higher powers. But, with low 

 powers, the possibility, however, seems to obtain that an object 

 observed through the Microscope appears to be more brightly 

 illuminated than when seen with the naked eye. If we assume 

 that the angle of aperture 30, contained in the above table, 

 corresponds to an objective-amplification of seventeen times, 

 which agrees with experiment, we obtain, with an eye-piece 

 amplification of about three times, an image-area which is 50 ! 

 2,500 times larger than the object, whilst the amount of light 

 utilized is about 3,500 times greater than in ordinary vision. 

 The brightness would accordingly be increased in the ratio of 

 to 25. But the question arises whether a cone of light 

 with an aperture of this size emerges sufficiently narrow from 

 the objective to be received by the pupfl of the eye; for it 

 is evident the above conclusion becomes illusory if that is not 



For the examination of this question we will construct the path 

 of rays in the Microscope according to the diagram above explained 

 (p. 41). Although, owing to want of space, the distances there 

 given do not coincide with the actual dimensions, the conclusions 



