By Colonel Sir Henry James
London   Longman, Green, Longman, And Roberts
13" x 10.5" xi, 624, [50]
The ordnance survey data for the relative levels of the land above sea level in the British Isles.
By Colonel Sir Henry James

1861 Abstracts Of The Principal Lines Of Spirit Levelling In England And Wales

London   Longman, Green, Longman, And Roberts
13" x 10.5" xi, 624, [50]
The ordnance survey data for the relative levels of the land above sea level in the British Isles.
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Description

Scarce

As explained in the introduction of the work: "The levels established on these lines...furnish definite points all over the kingdom from which the lines of levels for the contours and the detail plans of every part of the country are carried, and thus all the levels on the Ordnance plans refer to one common datum level." According to the Ordnance Survey: "Ordnance Survey Bench marks (BMs) are survey marks made by Ordnance Survey to record height above Ordnance Datum. If the exact height of one BM is known then the exact height of the next can be found by measuring the difference in heights, through a process of spirit levelling." Thus these volumes contain the fundamental data on which later measurements were made in the process of making ordnance survey maps. It was the culmination of 18 years of surveying. The second volume contains 24 folded plates of graphical representations of the measurements taken. This work is scarce. This copy belonged to Gloucester Public library, and contains library plates and stamps.

Condition

In the original cloth. Externally sound, with some bumping to the extremities and spine, and some marking to the boards. Both volumes have library plates to the front pastedowns and front free endpapers, and barcodes to the front free endpapers. There are also library stamps to the rear of the title pages, and to the reverse of each plate in volume two. Generally clean and bright, and generally firmly bound

Very Good

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