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I haven't had the chance to investigate your comments but I am not
married to my analysis of Bygrave's method. We both agree that one of
the scales is an inverse scale since they both run in the same
direction and that Bygrave didn't tell us that. When I tried to figure
it out I came to the conclusion that the tangent scale had been
inverted but I can see your point that it could be the cosine scale. I
think that I read that the Dennert & Pape MHR-1 has a co-tangent scale
and the Bygrave looks just like it so it made sense that the Bygrave
also had the inverse tan scale. I am planning to spend some time this
weekend really delving into this further.

I would appreciate a copy of Aquino's method, can you send it to me
off list?

I am really enjoying this deep analysis of the Bygrave slide rule and
it may turn out that Captain Bygrave was more brilliant than we
originally thought.

gl

On May 29, 2:39�pm,  wrote:
> It's just been drawn to my attention that in the book "Spherical 
Trigonometry" by J.H. Clough-Smith, on page 105, "Aquino's log tangent + log 
secant method" is described. It seems fairly clear that the Bygrave Slide 
Rule is based on this method, which talks about 'only needing tables of log 
secants and log tangents'.
>
> I rest my case. �Bygrave must have consciously changed the name 'secant' to 
'cosine' in his written descriptions.
>
> I have a .gif of this description but as a non-member I can't post it here.
>
> Peter Martinez
>
> --------------------------------------------------------
> [Sent from archive by: peter.martinez-AT-btinternet.com]
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