Can anyone explain some building terms, please?
An ancestor of mine was killed during the construction of Spa Mill in Ossett, WRY (there's a lot about the mill at
https://www.ossett.net/ossett_mills.html). He was a joiner, so had presumably been involved with the centres (framework) over which the arch was built. Unfortunately when these were removed the arch collapsed; his death certificate, quoting the Coroner, indicates that the arch was made of brick.
The fullest report I have found is in the Huddersfield and Holmfirth Examiner of 3 June 1854, part of which is as follows:
An arch, six yards span and about forty-eight feet in length, was being built, of which the part built up had been backed up nearly level with the centre. There were three windows in the arch on one side. A great portion of the upper end had been without centres for several days. On Tuesday afternoon the centres were lowered. In two or three minutes afterwards the whole of the arch suddenly fell in, and covered up the two men.... The stone walls from which the arch sprung had not given way at all.
The building isn't there now, but I imagine this would have been a large entrance passing through one of the mill buildings. 'Upper end' probably refers to the ground sloping down from the road. I'm not a builder or architect, so some of the terminology means little to me; 'centres' are explained on a number of websites, but what is meant by 'the part built up had been backed up nearly level with the centre'?