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Many thanks to Jan and Bruce for their replies. Unfortunately,
I am taking all data from tables in Brother Arnold's book, so Bruce's
suggestion, although most valid, is of no help. I have searched
my library, as well as the Internet, in an effort to obtain
understandable data (to me) regarding proportional logs, but have
so far been unsuccessful. If anyone out there can refer me to
a site or a publication that deals in depth with this subject, including
an explanation for dummies (that's me) on how to calculate these
logs, please give me a shout. These things seem to have passed
into antiquity without so much as an obituary, as respects navigation
- I find only diurnal proportional logs for use in astrological
calculations.
Thanks again to all.

On Thu, 26 Aug 2004 00:05:38 +0200 Jan Kalivoda 
writes:
> Yes, Henry, if you have computed the value 1' 30" for 30 degs
> yourself from the usual tables of the refraction and parallax and
> didn't taken it from some prepared table in your table set (as I
> supposed), this is a beautiful explanation.
>
> I have seen the term "PL" for other bases than 10800 secs, too. But
> not at the beginning of the 19th century and only in German, it's
> true.
>
> Hello, Bruce.
>
> Jan
>
>
> ----- Original Message -----
> From: "Bruce Stark" 
> To: 
> Sent: Wednesday, August 25, 2004 10:44 PM
> Subject: Re:       Proportional logs, etc.
>
>
> Henry,
>
> I'm thinking the problem comes from using a slightly different value
> of
> refraction. A change of less than one second of arc in the
> refraction correction
> would change the PL enough to make your calculation agree with that
> table.
>
> There were a number of ways of calculating refraction, and tables
> didn't
> always agree precisely.
>
> So far as I know, the term "Proportioning Logs" was used only for
> the kind
> you are familiar with, though the idea was used with other intervals.
>
> Bruce
>
>
>
>
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