At the Earth's Core by Edgar Rice Burroughs

I was born in Connecticut about thirty years ago. My name is David Innes. My father was a wealthy mine owner. When I was nineteen he died. All his property was to be mine when I had attained my majority -- provided that I had devoted the two years intervening in close application to the great business I was to inherit.

I did my best to fulfil the last wishes of my parent -- not because of the inheritance, but because I loved and honored my father. For six months I toiled in the mines and in the counting-rooms, for I wished to know every minute detail of the business.