Napier's logarithms  (1616, 1619) 1616 original definition and tables of logarithms

 (Text in html from the Netherlands).

A table (based on 100) that demonstrates the idea.

How would one use Napier's Tables:

Example: The rule of 3.
Suppose a/b = c/d.
Given any three of these values, find the fourth.

Napier's Theorem: If a/b=c/d then
NOG(a)- NOG(b) = NOG(c)-NOG(d)

Napier's logarithm tables.
 

Making Napier logarithm tables. (MS Excel)
 

How do Napier logarithms compare with modern logarithms?
 

The End