Rabdology

The devices themselves don't use logarithms, rather they are tools to reduce multiplication and division of natural numbers to simple addition and subtraction operations.

Napier coined the word rabdology (from Greek ῥάβδος [rhabdos], rod and λόγoς [logos] calculation or reckoning) to describe this technique.

The second device was a promptuary (Latin promptuarium meaning storehouse) and consisted of a large set of strips that could multiply multidigit numbers more easily than the bones.

An interesting tidbit is this treatise contains the earliest written reference to the decimal point (though its usage would not come into general use for another century).

Nevertheless, these devices (as indeed are logarithms) are examples of Napier's ingenious attempts to discover easier ways to multiply, divide and find roots of numbers.