Early tables resembling those of natural logarithms

That natural logarithms may be constructed from Napier's logarithms is no surprise to a modern mathematician, but the thought that this might have been done within ten years of Napier's original publication seems a historical impossibility, since by that time, most of the modern constituents of the notion had not been conceived. Nonetheless the practical use of Napier's tables required interpolation, and the systematization of that interpolation generated a new table with a remarkable similarity to natural logarithms. This interpolation table was later extended by Speidell to stand alongside his ‘New Logarithms’, as an alternative form.