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Eight Bygraves.
Six HR1s
Twelve MHR1s.
Three HR2s.

What a pitiful number of survivors.  It is even worse than I thought.
I wonder how many were made?
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I made an error again which should be corrected:-

I wrote:
"The explanation of Aquino's short-method of logTan / logCosecant  sight
reduction (I sent in a copy of the explanation recently from 'Spherical
Trigonometry' by J.H. Clough-Smith) makes the argument conclusive for me.
Aquino published his method a couple of decades later than Bygrave. In fact,
Aquino's method should perhaps really be called Bygrave's method,  as the
latter invented the principle of perpendicular from the observer's meridian
to the star meridian  firstly,  in 1921 (using a mechanical implementation)."
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This is quite wrong. I was assuming Clough-Smith was correct in his book 
(published 1966) which states "Aquino's Tabular Method ... first published in 
Rio de Janeiro in 1943".

I only learned from a posting here that Aquino first published the details of 
his method in 1908; and the tables were published by Potter in London in 
1918.  Thank you Mr. Waldendand for post 8770 with these details.
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This puts a completely different complexion on the development of the Bygrave slide rule.

It is not unreasonable to expect that Captain Bygrave was fully familiar with 
all contemporaneous developments in navigation.
The publishing of tables by Aquino in 1918 in London makes it as close a 
certainty as is possible, that he would have known of them and the principles 
of the method.
It is not unreasonable to extrapolate slightly further and suggest perhaps he 
started thinking about the mechanical implimentation of the method, which led 
to the development of the instrument.
This tends to add favour the logtan/logcosecant combination of scales 
arrangement for Bygrave... as in Aquino's log tan/logcosecant method.

Douglas Denny.
Chichester.  England.


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