The string that you see is the center line of the trestle and shows the height the trestle will be. At the end of the string (on the right) is the entrance to the tunnel. A pipe line, 36 inches in diameter, will come thru the tunnel onto the trestle., PCA0071-669, Box: PCA 71. Asa C. Baldwin Photograph Collection, ca. 1905-1943, PCA 71. Alaska State Library - Historical Collections Finding Aids. https://alaska.libraryhost.com/repositories/2/archival_objects/41350 Accessed November 24, 2024.