Around 1800 (plus or minus about 5 years) is when it was estimated that the world's population had reached 1 billion.
A mountain peak on a topographic map a mountain would be represented by parallel contours of elevation according to the shape of the peak and the overall shape would be coming to a point or the peak of the mountain and since it is a mountain the contours would be fairly close together.
He got it at the cave Hira
