ItemarU on Prof. Ahhes Note, d'c. By Br. E. GUtaij. liGo 



of Prof. Abbe does not essentially differ from the older one. For it 

 is clear that (fig. 223) : 



, , BO 



tan ^=013; 



substituting this in the equation of Prof. Abbe : 



taI^-.t' 1 



we get 



or, 



_BC 1 



CD xh~ r 



BC 



h 



CD 

 / 



BC 



Now, —r- is nothing else than the actual amjDlification of the 

 object of the length E F = A, placed at E ; if, therefore, C D = the 



Fig. 223. 



Er~ 



usual distance for which the *' linear amplification " is determined, 



R C 

 then —7- is the " linear amplification " itself. And as in this 



case C D is a constant value, say C, we get, 



BC _ 1 



wherefrom it is directly concluded, that the amplification numbers 

 of Prof. Abbe (expressed by ^ ) and those obtained by the old mode 



fby-7-j are in a constant relation. If, therefore. Prof. Abbe 



Ser. 2.— Vol. V. 



3 E 



