How was the indus valley discovered?

A British traveler named Charles Masson unwittingly stumbled upon what would lead to uncovering the Indus Valley when he encountered several mounds of bricks in India in the 1820s. Three decades later, engineers building a railroad through the same area found more of these bricks, which eventually prompted archaeologists to investigate. The bricks, it turned out, were part of the Indus Valley civilization.