When the
Beagle sailed out of
Devonport on 27th December 1831,
Charles Darwin was twenty-two
and setting off on the voyage of a lifetime. The journal that he kept shows a naturalist making patient
observations concerning geology and natural history as well as people, places and events.
H.M.S. Beagle arrived at the
Cape Verde Islands on 16 January 1832 and anchored at
Porto Praya,
on the island of
Santiago (spelled St. Jago, in Darwin's narrative). Darwin went ashore with two officers and rode to
the village of
Ribeira Grande, a few miles east of Porto Praya, to visit some Spanish ruins there, and
returned to Porto Praya the next morning. On another day Darwin headed for
St. Domingo, but became lost
along the way and ended up at the village of Fuentes before heading back to the Beagle.
It was on
Santiago that Darwin made his first curious discovery. He found a horizontal white band of shells
within a cliff face along the shoreline of Porto Praya. The fact that this layer was forty-five feet above
sea level raised some interesting questions for Darwin.
- It was obvious that this layer of shells was at one time under the ocean. How did it end up
forty-five feet above sea level?
- Was it possible that small upward movements of the land raised the shell layer? More violent movements
of the earth would have otherwise broken up the nearly horizontal line of shells.
The arrangement of the shell layer appeared to support Lyell's theory of a world slowly changing over
great periods of time, a novel concept in Darwin's day. This observation, and many others like it, would
later lead Darwin to develop his own theory of
Raising Continents and Sinking Ocean Floors.