We always read about "ancient knowledge" and how there may be more of it yet to discover. For those who scoff, I offer this concrete example, and I do mean concrete. I was watching a show on ancient buildings and the subject of concrete and cement came up. I spent til 1:30 in the morning reading up on it and found that the Romans had concrete that could dry or set up under water, but after their civilization collapsed that knowledge was hidden until the mid 1750s when a Scotsman (of course) rediscovered it.
The Romans used volcanic ash. This gentleman used the slag left over from iron smelting. Turns out both substances had silica in them and that is what made the under water drying possible. So anytime anyone says there's no such thing as ancient knowledge being rediscovered . . . NOT!
I will be covering this story in our "game changers" issue for March.