The sixteenth century Alderney crystal: a calcite as an efficient reference optical compass? by...

The sixteenth century Alderney crystal: a calcite as an efficient reference optical compass?

by Albert Le Floch, Guy Ropars, Jacques Lucas, Steve Wright, Trevor Davenport, Michael Corfield, and Michael Harrisson

Proceedings AVolume 469(2153):20120651

May 8, 2013

©2013 by The Royal Society

(a) The Alderney crystal (5×3×2.3 cm).

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Case of an unpolarized light impinging on a calcite crystal.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Case of a linearly polarized light.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

(a) Case of a partially polarized light.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Inductive coupled plasma-atomic emission spectroscopy (ICP-AES) spectra for the bulk of a freshly collected calcite crystal and of the Alderney crystal.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Mg2+–Ca2+ exchanges on calcite surface for a crystal partially immersed in a solution of MgNO3 in water.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Mg2+–Ca2+ exchanges on calcite surface for a crystal partially immersed in sea water.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Comparative roughness measurements obtained with a Taylor-Hobson surface profiler.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Typical perturbations of a magnetic compass by one of the excavated cannon of the Alderney ship.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Typical measured sky irradiances at twilight on 18 April 2011 at 48°07′ N, 1°41′ W. (a) The successive photographs are taken within 10 min intervals.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Typical bearing of the Sun at 22.16 during twilight for low irradiances.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Sun tracking experiment (see panel a).

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society

Heating of a calcite crystal.

Albert Le Floch et al. Proc. R. Soc. A 2013;469:20120651

©2013 by The Royal Society