Description: PC0002 Image no. 198. East portal of Summit Tunnel western summit length 1660 feet
Photographer/artist: Alfred A. Hart
Date taken: 1860s
Photo location: Summit Tunnel
Type: photo
Subject: Transcontinental Railroad Construction
County: Placer
Source: Stanford Collection
References:
Contributor: Stanford Libraries
Notes: Original image is 3.9 MB. HCS 1/13/2022. Image at Stanford site. See also Goldbaum and Huffman's 2012 book, Waiting for the Cars, p. 244. The authors further explain: "Using black powder, the headings were driven an average of 1.18 feet per day per face. On February 9, 1867 nitroglycerin was first used in Summit Tunnel. With nitro, the daily advance per face was increased to 1.82 feet.
Mindful of the devastating explosion of nitroglycerin being shipped through downtown San Francisco in 1866, the railroad hired chemist James Howden to manufacture nitroglycerin right at the tunnel. The company paid him $300 per month in addition to the $500 paid in royalties for use of the patented formula."
The authors continued: "The advantage of nitroglycerin was that, with its greater power, the holes for the charges could be smaller, and thus drilled faster. In working the faces with nitro, holes 1 1/4 inches in diameter were drilled - half the size required for black powder. Furthermore, because nitro broke the rock into smaller pieces, less time was needed to clear the rubble. Nitroglycerin produced less smoke to foul the air, but it caused headaches. ... Nitro was carefully poured into the vertical holes through funnel and an iron tube. The tube and cold temperature within the tunnel slowed the flow of the viscous oil. Nitro was detonated with common blasting power in cartridges."
Hart's image no. 211, West Portal Tunnel no. 1 is referred to as the West Portal, sometimes Grizzly Peak. The authors note that in 1913, the railroad was rebuilt between Rocklin and Colfax and resulted in a shortening of the line.
Rights: NOT FOR SALE; research only
Identifier: AAH0032
Serial Number: 2086
Donation: Alfred A. Hart Collection (AAH) collection (#34)
