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I concur with Mr. Kolbe regarding Sir R.Knox-Johnstone's involvement in a the 
project mentioned with a re-constructed Viking ship.

The sun compass mentioned here I am farily sure had an article regarding this 
device in the Institute of Navigation journal around that time, and I 
probably have a copy here. If I find it I will post the reference or scan it.

I went to a lecture by Sir R.K-J at Warshash, some time around then, and the 
sun-compass and its use was discussed.

He also mentioned there was speculation about the possible knowledge and use 
of Icelandic Spar  i.e.  calcite crystal,  which is an excellent polariser 
(used to be used in microscopes until polaroid was invented) and that it 
could give a good indication of the position of the sun even through cloud 
due to the polariation of the light which is still present and detectable.  
The sun-compass, therefore it was suggested, was used when the sun was 
visible; and the calcite crystal when it was not.

A whole large crystal needs to be used, (which can be found naturally as they 
are relatively common), and more to the point has to be cut correctly (and 
therefore polished somehow) to obtain the polarising effect. Hence much 
speculation as to the possibility of its use.

Douglas Denny.

Chichester. England.


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