"# 745 Drilling Jumbo in operation in the face of one
of the Diversion Tunnels. From 20 to 25 drills can be operated at once and one-half of the face drilled in one operation. December 8th, 1931.
# 671 View of the drilling Jumbo taken outside the
Diversion Tunnels. It is of welded steel con¬struction, mounted on a truck chassis. December 13th, 1931.
# 747 Another view of a drilling Jumbo, backed up to the tunnel--face, showing the method of con¬struction and mounting. December 8th, 1931.
# 748 100-ton Marion Electric Shovel excavating blasted rock from one of the Diversion Tunnels. A three-and a half cubic yard dipper is used on these shovels. December 8th, 1931."
black and white photographs 4 x 5.3 in. or 8 x 4.8 in. paper background 10 x 13.5 in.
Archived TIFF images were scanned by Kathleen Broeder at 400 dpi with an Epson Expression 10000XL scanner. Digital images were reformatted in Photoshop. JPG and PDF files were then created for general use.