. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. WaCer Lesel (for brainaye) / en 600 {v> 1 Fig. 1.—Diagrammat (Not to Scate) ction to illustrate method of constructing tunnel below river bed. standing every precaution being taken, all the men engaged in driving the drainage heading by means of a tunneling machine have died; and in the case of the first Vyrnwy tunnel crossing of the River Mersey—driving by Greathead shield under pressure—the mortality was great. Having explained in very
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. WaCer Lesel (for brainaye) / en 600 {v> 1 Fig. 1.—Diagrammat (Not to Scate) ction to illustrate method of constructing tunnel below river bed. standing every precaution being taken, all the men engaged in driving the drainage heading by means of a tunneling machine have died; and in the case of the first Vyrnwy tunnel crossing of the River Mersey—driving by Greathead shield under pressure—the mortality was great. Having explained in very general terms some of the difficulties of tunnel construction, we will proceed to the case of the great tunnels through the Alps, and for the purpose of rendering the subject more easily intelligible, the following particulars may be given: Length of tunnel in miles North r east portal above sea level South or west portal above sea level do Highest level Maximum grade in tunnel per 1,000 Maximum height of mountain above tunnel Possible maximum tempera lure of rock deg. ard. 3,039 .;, t:>7 3,788 5, 598 85 Mont Cenis. Arlberg. 3,766 1,164 4,12-18 30 :.. 128 85 4,296 3,998 4,300 15 2, 362 65 Simplon. 2, 2o4 2,080 2,314 7 7,005 104. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Board of Regents; United States National Museum. Report of the U. S. National Museum; Smithsonian Institution. Report of the Secretary. Washington : Smithsonian Institution
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