Richard Dixon Oldham is credited with discovering the two main types of body waves -- elastic shock waves that travel through the Earth during earthquakes. The first of these waves is called a P , or Primary wave, because, due to its rate of propagation, it is the first wave to arrive at a seismograph. The second variety is called the S, or Secondary wave, which arrives after the inital P waves and vibrates at right angles to the direction of the travel. Oldham's interest in seismology developed from a distinguished background in geology.

Oldham was born in Ireland in 1858, and his father, who was a well-known geologist and professor at Trinity College in Dublin, encouraged Oldham's interest in geology. Oldham was educated in England, first at Rugby and later at the Royal School of Mines. In 1879 he traveled to India to resume the work of his father, who...