GV—50 PHOTOGRAMMETRIC ENGINEERING 
  
Fic. 4. Optical micrographs made from shadowed negative replicas. 
Collodion replica of the external surface of a tooth, showing the irregular junction between 
the enamel of the crown (above) and the cementum of the root (below). 105 X. 
Collodion replica of the surface of a ground cross-section through a tooth, showing the re- 
gion of the junction between dentin (above) and enamel (below). 105 X. 
Cellulose acetate replica of the etched surface of a copper rotogravure printing cylinder. 
The square elevations, representing depressions in the copper, are the minute wells in which 
ink is held. 105 X. 
Cellulose acetate replicas of the surfaces of two bullets fired from the same revolver. Many 
points of structural similarity can be noted. In order to show the entire replicas the mag- 
nification has been reduced photographically to 3X. 
NN 
AX 
A C. 
t m 
D ms 
me 
—