What made Egypt great is this stuff - silt. It's a rich supermineral silt, it's like an expresso, tiny flakes of rock and minerals that the river picked up over its wondering course and swept along with the flow.

 

All rivers carry some silt, but the Nile has the benefit of starting in Ethiopia, where the rock is young and volcanic. This forms the richness of silts. A hundred and forty million tons of this stuff are carried by Nile down river to Egypt each year. Every year, the seasonal flood covered the fields and left behind nutrient-rich silt that fertilized the crops. The more silt, the more food was produced. It was the size of the flood and with it, the bounty of silt, that the Nilometer was used to predict. 

 

So simply by measuring the heights of the Nile, the Egyptians were able to forecast food production and with it, the profits of the farmers. Each year, they used this information to set tax levels. So the wealth and the might and the splendor of the Ancient Egypt is all down to a simple twist of geographical feed. In fact Ethiopia itself gets almost no benefit from that fertile soil washed off its highlands. It’s even said that ,"It’s greatest export is the silt that it sends down the Nile. Silt, that made the Pharaohs rich.

 

But the ebb and flow of the Nile had more far-reaching implications for the Egyptian people than mere taxes. Intriguingly, maybe that where access to water is limited that actually determines the way a society is organized, even its use of slavery. Where water is in short supply or from a single source as it is in Egypt, you need a highly structured society to get the best out of it.

 

A lot of skilled irrigation - you need bureaucrats to decide where they think the water channels; you need teams of working men, slaves ready to do actual hard work in digging. And once a channel is in place; you need farmers with money enough to buy the water that it delivered. So right away you've got three tiers of society, and I haven't even mentioned the Pharaohs.