28 June 2013

Post 9) Getting it right…..or don’t believe all the facts

     I’ve been working my way around the centre, (St Augustine’s Trench) building by building and my last post was the image of the John’s Porter House and Severn Tavern façade on the north corner of Zed Alley. Pickfords, directly north again next door is also now in the bag (below) and then I started on Stone Bridge, before tackling the giant ten storey sugar house at quays head.

      After a while things weren’t adding up and I decided to cross check what i'd worked out as the the modern water level in the float with that of Jessop’s 1793 plan of the Avon and Frome; from Rownham ferry to Temple Backs and Traitors Bridge (Wade St)

     It turns out that the quay gauge normally read 15 feet in 1793, increased to 16 feet in the 1820s. The Quay gauge at the end of Narrow Quay by the Arnolfini (Acramans Anchor and chain warehouse) or Prince St bridge pier was an iron wheel linked to a float that read the height of water in the Frome like a clock hand. Zero on the quay gauge being low tide on the Frome.

     I cross checked all the land measurements of Jessop’s cross sections with the 1885 1:500 Ordnance Survey spot heights and found that the water level in the Floating harbour was kept at 19’4” above Ordnance Datum as opposed to 22’4” which i'd previously incorrectly worked out, a difference of three feet! So 19’4” AOD was 16 feet on the gauge in the 1820s. I should have remembered my modern quay gauge photo below north east of St Philip's bridge!

     I will now have to go back and redo the arches and approach ramp from Clare Street on my model of the Drawbridge as they are too flat! (Below)
     With this important matter out of the way, I decided to begin work on Bristol Bridge as a showcase model and new header image for this blog.

     Bristol Bridge has been rather difficult to get right. Fifteen hours of cross checking photos from my ferry trip, city walks, 1768 plans and 1885 and 2013 maps all threw up anomalies. The size of the arches has been the cause of the problem, hindering the start of my model. The 1793 Matthews Guide and all subsequent publications that copied the original disclosed dimensions are wrong. The main span was quoted at 55 feet and the two side arches at 40 feet from the springing. This may have been a case of rounding off. Both measurements as built are actually a few feet out, which is why I could not fit the three arches and two piers and two abutments into the physical 165’8” from the old St Nicholas pier wall to the 1723 Redcliffe river wall available.

     So cross checking sources and getting it right could make all the difference to a whole street of models being out, especially where you have vanished buildings and only watercolours and a line on a map as evidence of what they looked like.

     The Bristol bridge model is now coming on well. Below is a weigh house with weighbridge, nearing completion, that stood on the southwest corner of Bristol Bridge nearest St Nicholas Church from approximately 1816-20 until the 1860s/70s widening of Bristol Bridge and Baldwin Street.
     It was drawn by Architect James Foster in March 1816 and appears in watercolours by Rowbotham and Delamotte next to the Oyster Women’s shed. Two other Weigh Houses stood at Broad Quay as drawn by Hugh O’Neill and Temple Gate, (location yet to be found) Whether or not Foster designed it for Parnall's of Narrow Wine Street remains to be seen as they did not start business until 1820.

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