Press: RareBooksClub.com (May 11, 2012)
Author Name:Clark, Edwin
This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book (without typos) from the publisher.
1850 Excerpt: ...ten days of intense anxiety.
The tube was supported at each end on piers of sandstone, built for the purpose, to within 20 inches below the bottom of the tube.
They were 12 feet high, and 18 feet by 9 feet in plan at the top, with a slight batter.
A layer of elm planking was placed on the pier 2 inches thick; folding wedges of American elm 10 inches square at the larger end, and 7 by 10 at the smaller end, and 10 feet long, were then driven longitudinally between the bottom of the tube and the planking, the lower wedge only being driven, the upper one being accurately fitted to the bottom of the tube.
These wedges were driven by a battering-ram.
Previous to the driving of these wedges, some portion of the centre of the platform was removed for a space of 112 feet: the deflection was one inch and a quarter; the curve was, however, irregular.
The great extra weight thrown on the remainder of the platform became very evident.
After driving the wedges, and further removing the platform, as the tube descended and compressed the remainder of the timber, the difficulty of extracting it became greater and greater, and the timbers were cut out piecemeal.
They became at length so compressed that great difficulty was experienced even in this operation.
A hole drilled with an augur was immediately filled up by the pressure, so that it was impossible to bore to any depth; and great labour was required to splinter away the timber in small fragments.
The descent of the tube from its own weight was watched constantly with the greatest anxiety, as the operation proceeded at length night and day.
The great problem was now being solved.
Many had predicted a deflection of two or three feet, and a great number of high authorities had affirmed that the tube could not support its...
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