Dismantled the remaining three nearside half-drop windows today.  Salvaged the glass that was usable  and the brass channel from the top rail of two of them.  The third was so choked with decomposed rubber that I left it for another time.   Cut up the rusty steel into easily-disposed-of pieces ready to take to the tip.  Started to scrape the corrosion from the alloy fixed glazing bottom clamp bars.