So, Belfast was a county then?!
I reckon it was an attempt to establish Belfast at either end of a line through the centre of the Earth, around which the globe would then spin.
[Some of us think the World of Belfast ... probably something to do with having been born there! ]
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There are many Belfasts around the world.
A search with e.g.
www.multimap.com will throw up 17 off, most in America.
[The one in Oz was interesting 'cos it is no longer extant - took a while to track it down. The town of Penshurst lies inland.]
You can also use that online tool to look at the 1:100,00 or 1:50,000 scale maps of Belfast.
The County border seems to be a dashed green line, running mostly down the West bank of the Laggan.
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The latter scale map is available in physical form on ...
Sheet 15
DISCOVERER SERIES
ORDNANCE SURVEY OF NORTHERN IRELAND
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Much earlier, the 6" OS maps accompanying the 1830s OS Memoirs of Ireland are available in huge volumes at PRONI in Belfast and at The National Archives in Kew, London.
The ones covering the County border through Belfast are nos. 61, 64 & 65.
[N.B. Very very large & very very expensive to get reproduced. Not sure whether they show the border explicitly.]
Unfortunately the OS Memoir for the parish of Shankill on the Co. Antrim side was never published.
The one for Knockbreda on the Co. Down side would be in the Co. Down 2 Vol. 7 volume.
www.booksireland.org.ukHowever, these memoirs tend not to mention boundaries much, nor indeed even townlands.
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There were many squabbles about boundaries between CHICHESTER, HAMILTON, MONTGOMERY et al after the Plantation.
One contentious area (not Belfast) was the subject of one of Nicholas CRANE's recent "MAP MAN" programmes on TV.
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John