The Great Hoosac Tunnel.
Messrs. Editors:--In No. 23, Vol. XVII., of your paper, is an article upon the Hoosac Tunnel, but made up from data nearly a year old, and consequently not correctly representing the tunnel as it is at the present time. Your conclusions of course were based upon the same data; but during the past year, and especially during the past five months, much greater progress has been made than ever before upon the work, and a knowledge of what has been done since the last report was issued will, I think, give you a different impression of the time required for its final completion.
Referring to the profile in that number of the SCIENTIFIC AMERICAN, the following are the distances to the various points where the work is being prosecuted:
Distance from east end to central shaft 12,837.294 feet
" " central shaft to west shaft 9,747.072 "
" " west shaft to new shaft 265.000 "
" " new shaft to well No. 4 659.150 "
" " well No. 4 to pier[1] 1,522.825 "
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" " east end to pier[1] 25,031.341 "
[Footnote 1: The instrument pier is 4 feet west of the present west end of the tunnel.]
The following are the lengths of the headings at the various points of the work, Dec. 2, 1867:
Length of east end heading 4,608.000 feet
" " west shaft, east heading 1,262.000 "
" " " " west heading 611.000 "
" " west end heading 617.000 "
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Total length of headings 7,098.000 "
Leaving 17,933.341 "
or 3,396 miles of heading yet to be made, of which 1,218.975 feet are between the west end and the west shaft, and 16,714.366 feet between the west shaft and east end of the tunnel.
The central shaft is down 583 feet, and well No. 4 is down 150 feet.
The progress for the month of November, 1867, was as follows:
East end heading 126.00 feet
West shaft, east heading 33.00 "
" " west heading 5.00 "
West end 20.00 "
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Total for the month of November 184.00 "
Thirty feet of brick arch were completed during the month at the west end, making a total of 516 feet of brick arch completed to date.
The progress for the last six months has been as follows:
East end 711.00 feet
West shaft, east heading 216.00 "
" " west " 288.00 "
West end 180.00 "
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Total, from June 1, to Dec. 2 1,395.00 "
" for the previous six months 632.00 "
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" " year ending Dec. 2, 1867 2,027.00 "
The new shaft has been sunk, and at its foot are the pumps which, together with those at the west shaft, are now throwing out between 900 and 1,000 gallons of water per minute.
During the last month great quantities of water were struck at both headings of the west shaft (70 gallons per minute at the east heading in one day), and the work was stopped in consequence, which accounts for the small progress at this point. A new pump of 1,000 gallons per minute capacity will be at work, in addition to the above, in a few days, and the work can then go forward with increased rapidity.
Well No. 4 is an artesian well, which is now being carried down as a shaft to afford two more faces to work from. Its depth will be, when finished, 215 feet, its dimensions 8 by 8 feet.
At the rate of progress for the past year it will require but eight years and ten months to pierce through the mountain and at the rate for the past six months it will require but six years and five months. But when the central shaft and well No. 4 are sunk to grade the number of faces to work from will be doubled, and the time of completion thereby greatly diminished. At present drilling machines are employed only at the east end, but in a few weeks they will be used at the west shaft, and also at the central shaft as soon as the buildings and machinery are again in place, and this again will hasten the completion of the work. At the west shaft buildings are already erected for the manufacture of nitro-glycerin, and the use of this powerful explosive will be adopted during the present month. In fine, every means that will hasten the work will be employed, and ere the present generation passes away, and even within from four to seven years, trains loaded with freights and passengers will pass and repass through the great heart of the Hoosac Mountain as an hourly occurrence.
A. BEARDSLEY, C. E., Asst. Engineer.
North Adams, Mass.