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Frank,

I don't believe it was a matter of the English manufacturers shunning patent
royalties; it is more likely that micrometer sextants were generally
considered to be less accurate than vernier sextants. The 1930 article that
George sent states this very clearly and in fact announces that Heath has
overcome the problems leading to inaccuracies (backlash, "pull" on the
sextant centre etc.). Even in the Plath patent description of 1921 the
vernier is described as being more accurate, it says that the micrometer has
been added to be able to get a quick reading when no high accuracy is
required.

Wolfgang

-----Urspr�ngliche Nachricht-----
Von: NavList@fer3.com [mailto:NavList@fer3.com]Im
Auftrag von frankreed@HistoricalAtlas.net
Gesendet: Montag, 5. November 2007 03:34
An: NavList@fer3.com
Betreff: [NavList 3780] Re: micrometer sextants.



Of the 1930 Brown's Nautical Almanac, I wrote:
"One ad shows a high-end vernier sextant that has a micrometer drum, too."

And Wolfgang added:
"That was patented by C.Plath in 1921."

So then perhaps the delay in English sextants was simply because no English
manufacturer was willing to pay patent royalties until they knew there was
strong market demand for micrometer sextants (??). And about Plath, do you
know: did they begin manufacturing such sextants in 1921? Or was that the
patent date only?

 -FER
http://www.HistoricalAtlas.com/lunars




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