Figure 12.—Works at the central shaft, Hoosac Tunnel, for hoisting, pumping and air compressing machinery, and general repair, 1871. (Photo courtesy of State Library, Commonwealth of Massachusetts.)
Figure 13.—Hoosac Tunnel. Air-compressor building on Hoosac River near North Adams. The compressors were driven partially by waterpower, derived from the river. (Photo courtesy of State Library, Commonwealth of Massachusetts.)
Figure 14.—West portal of Hoosac Tunnel before completion, 1868, showing six rings of lining brick. (Photo courtesy of State Library, Commonwealth of Massachusetts.)
When the Shanleys took the work over in 1868, following political difficulties attending operation by the State, the period of experimentation was over. The tunnel was being advanced by totally modern methods, and to the present day the overall concepts have remained fundamentally unaltered: the Burleigh piston drill has been replaced by the lighter hammer drill; the Doane drill carriage by the more flexible “jumbo”;nitroglycerine by its more stable descendant dynamite and its alternatives; and static-electric blasting machines by more dependable magnetoelectric. But these are all in the nature of improvements, not innovations.
Unlike the preceding model, there was good documentation for this one. Also, the Hoosac was apparently the first American tunnel to be well recorded photographically. Early flashlight views exist of the drills working at the heading ([fig. 6]) as well as of the portals, the winding and pumping works at the central shaft, and much of the machinery and associated aspects of the project. These and copies of drawings of much of Doane’s experimental apparatus, a rare technological record, are preserved at the Massachusetts State Library.