a. Sample location.
b. Thin sections in photographed natural light (right) and between crossed
Figure 20. Sample M3, taken from beneath the barrel of the 5-in. gun (scale
in millimeters). Thick sections taken in natural light are not available for
Figure 21. Sample M5, a vertical sample taken from the front of the 5-in.
gun housing. No thick section or location photographs are available. Thick-
ness was only 0.6 cm, and it was obtained at nearly the same location as
February sample F8. Right to left are thin sections photographed in natural
light and between crossed polarizers, respectively (scale in millimeters).