X-RAY iMICKOSCOPY 





iW^ 



fffl- 



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Fig. 13. Wood splinters. (T.P.D. microscope.) 



Fig. 14. Ant. (T.P.D. microscope.) 



spatial distribution of the specimen out of a 

 print. This is clearly illustrated in Fig. 3. 



The large depth of field, however, is espe- 

 cially important for stereomicroscopy in 

 which the specimen is seen in its right pro- 

 portion, but on a larger scale. The geometri- 

 cal conditions for this can easily be deducted 

 from Fig. 16. Assume that the M times mag- 

 nified specimen is placed at a distance / from 

 the observer (Fig. 16a). Let the maximum 

 angle of convergence be (p. Thus tan (p = 

 e/2l, in which e is the interocular distance. 



Fig. 15. Pu.sterior end of a mosquito. 



b •cts tftpitcts Mm 



c point sources 

 ■ \ / 



Fig. 16. Condition for making stereographs. 



670 



