Answer:
Because there are four corners of the universe and there are four principal winds, and therefore there can be only four gospels that are authentic.
Explanation:
MY LIFE I DONT HAVE. (yet)
The answer is: Improvements in engineering methods.
In order to build a canal, advanced engineering methods are needed to creates dams and locks so we can stretches the slack water levels of the canals. This would be impossible with traditional engineering method.
Beside that, advanced engineering methods also reduce the time needed for the projects and reduce the cost of building the canals.