This is part of the collection of the Los Angeles Department of Water and  Power, which has the single largest collection of Bledsoe’s work that I have seen. Their collection is now held by the California Historical Society, and is archived, curated, and conserved by the University of Southern California library. It shows the construction of the Los Angeles Aqueduct. The original images were on 6×8 glass plates, but these are rarely handled, and most images (including this one) have been scanned from internegatives or prints and have lost image quality along the way.

This is the library’s description of the image: Photograph of a view of construction of the Los Angeles Aqueduct, showing a wooden track, ca.1910-1920. A large, riveted pipe, supported by concrete blocks, runs from the left foreground to the hill that sits at the center background. A wooden track runs along the ground, parallel to the pipe. In the center of the image, two men lean on a cart that rests on the track. A metal apparatus with cables extending from the top, apparently used to hoist beams, sits to the right of the track. Hills are visible in the distance.

Photograph by J.W. Bledsoe

From the California Historical Society Collection at the University of Southern California

http://digitallibrary.usc.edu/cdm/singleitem/collection/p15799coll65/id/3551/rec/6