coal and wood ash?

Not sure about the victorian way of doing things but I always save the potash from wood/paper buring to put on the veggie patch.  Any coal makes a fantastic path base, or if you have heavy clay I have used it there to break it up.  Mix the potash in with poultry manure and hey presto you will have 'jack in the beanstalk' veggies. 

"How often" depends on your soil; it will leach away much faster in free-draining soil than heavy clay.

This link has some interesting info about the nutrients in wood ash compared to ground limestone (wood ash being surprisingly high in calcium (lime), limestone having a number of useful minerals other than calcium in it).

Both of these will raise the pH of your soil, which may or may not be what you want; extra lime is good for brassicas, bad for spuds.

The Crystal Palace for the 1851 Great Exhibition was built of iron and glass Zippy. A million square feet of plate glass. This was a demonstration of the new technical capacity for factory glass production and helped set the fashion for more plate glass and bigger windows so you are possibly thinking of the previous century.

My point was not an argument to follow the Victorians slavishly but not arrogantly to ignore their practice where it was based on experience and worked.

My point about rejecting good experience was not aimed at Zippy. Sorry Z if it seemed that way.
There were few ages more science smitten than the Victorians - we are at least as inclined to believe in magic additives and super foods!