I haven't actually got around to reading Mystery Of The Cathdrals cover to cover again but this is the second time Fulcanelli implies a deeper link between gothic architecture, alchemy and specifically Solomnic magic
'The Labyrinth of Solomon...is a cabalistic figure found at the head
of certain alchemical manuscripts and which is part of the magic
tradition associated with the name of Solomon.'
He also discusses the origin of the word Gothic and seems to imply that the Cathedrals were not only alchemical 'textbooks in stone' but perhaps grimoires