# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: napier and logarithms
From: Paul Hirose
Date: 2009 May 29, 21:12 -0700

```corallina wrote:
> I worked the sqrt of 100000 in about 2 hours.

How did you do it? As a schoolboy I was taught a method similar to long
division, but all I can remember now is that it began by grouping the
digits in pairs.

> Also this leads to the question as to whether Napier or Briggs were
> able to find the value of log(2) or log(3) to 7 decimal places or did
> that have to wait for Euler.

Briggs published 14-place logs of the numbers from 1 to 20000 and 90000
to 100000 in 1624. Adrian Vlacq filled the gap in 1628 with a 10-place
table.

> After receiving my slide rule in the mail and trying a few
> calculations, I have decided that weak eyesight precludes this method.

As a teen I could read a slide rule easily, but now at age 52 it's
impossible without help, though my distant vision is fine. A pair of
reading glasses (+2.0 diopter) takes care of that problem. That's a
little too strong a correction for viewing a computer monitor, but a
slide rule is used at shorter distance.

Sometimes I use a large, low power, hands free magnifying glass plus
reading glasses. That extracts all the potential of the slide rule
without eyestrain.

The following 1872 article from the MNRAS mentions the Briggs and Vlacq
tables. "With the exception of Vega's Thesaurus &c., the only complete
table of ten figure logarithms that has been published is the original
one, partially calculated by Briggs and completed by Vlacq... It is not
a little remarkable that the most accessible table of ten-figure
logarithms we possess should have been published nearly 250 years ago.
This places their use out of the power of all who have not access to an
important library."

I was surprised to find "Arithmetica Logarithmica" by Briggs (1624) on
Google books. The original must be quite valuable.

The seminal work by Napier is also on Google, in an 1889 English
translation:

There are a lot of logarithm and log trig tables on Google. Anyone who
wants to reduce a sight the old fashioned way will have plenty of
choices, though reading these tables over the web may be clumsy without
a high speed connection.

--
I filter out messages with attachments or HTML.

--~--~---------~--~----~------------~-------~--~----~
To post, email NavList@fer3.com
To unsubscribe, email NavList-unsubscribe@fer3.com
-~----------~----~----~----~------~----~------~--~---

```
Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)