Posts Tagged ‘Charles Darwin’

Charles Darwin’s Birthday

Friday, February 12th, 2010

Today is the 201st anniversary of the birth of Charles Darwin, ‘Father of Evolution’. His voyage on HMS Beagle from 1831-1836 is being retraced by Randstad Clipper Stad Amsterdam, with his great-great-granddaughter Sarah Darwin and a group of scientists and researchers aboard. This beautiful clipper arrives in Sydney tomorrow for a four day stay.

Magnetism

Friday, January 23rd, 2009

I’ve just finished reading A Pirate of Exquisite Mind: The Life of William Dampier: Explorer, Naturalist, and Buccaneer by Diana and Michael Preston. I was very impressed to read of the meticulous observations that Dampier made. In fact, his writings were carried by Charles Darwin on his voyage on the Beagle and held in high esteem by sailors such as Cook and Nelson. I knew that Dampier had charted part of the Western Australian coast in the 1685 but not that he made three circumnavigations.

My only quibble with an otherwise excellent book was the authors’ confusion between variation and deviation. As Matthew Flinders observed and defined deviation in the early 19th century, it is unlikely that the crew onboard with Dampier would have moved iron objects away from the compass to avoid its effects.

To clarify the two terms I have extracted the definitions below from The Language of the Sea*.

Variation. The angle between magnetic north and true north, it varies in different parts of the world, and may be either easterly or westerly. It is caused by the magnetism of the Earth.

Deviation. The amount of deflection of a compass needle caused by the magnetism of the vessel itself. The deviation is different according to the vessel’s heading.

There is much greater detail about these two concepts in Navigation and Passage Planning.

*Found in Skipper and Crew, Knots and The Language of the Sea.