Fig- 73 - I did mention some time back that if I were to build this again, then I would not start in the centre, but at one end and work out from there.  It is at this stage that we see the reason why.  Iron construction, consists of joining lengths of iron together, be it plate, bulb iron or angle iron, the lengths, other than for plate, being of about 40 feet long.  The practice is that there is a minimum distance between these butt joins, in the main it is the distance of two frames, or 4 fee