The construction of the wonderful canon of logarithms

88 Notes.
God) in a second Edition, to set out such Logarithmes as shal make those
numbers aboue written to fall upon decimal numbers, such as 100,000,000,
200,000,000, 300,000,000, &c., which are easie to bee added or abated to or
from any other number.
V. From the DEDICATION OF RABDOLOGIM.
Most Illustrious Sir, I have always endeavoured according to my strength
and the measure of my ability to do away with the difficulty and tediousness of
calculations, the irksomeness of which is wont to deter very many from the
study of mathematics. With this aim before me, I undertook the publication
of the Canon of Logarithms which I had worked at for a long time in former
years ; this canon rejected the natural numbers and the more difficult operations
performed by them, substituting others which bring out the same results
by easy additions, subtractions, and divisions by two and by three. We have
now also found out a better kind of logarithms, and have determined (if God
grant a continuance of life and health) to make known their method of construction
and use ; but, owing to our bodily weakness, we leave the actual computation
of the new canon to others skilled in this kind of work, more particularly
to that very learned scholar, my very dear friend, Henry Briggs, public Professor
of Geometry in London.
Notation of Decimal
Fractions.
In the actual work of computing the Canon of Logarithms, Napier
would continually make use of numbers extending to a great many
places, and it was then no doubt that the simple device occurred to
him of using a point to separate their integral and fractional parts.
It would thus appear that in the working out of his
great invention of
Logarithms, he was led to devise the system of notation for decimal
fractions which has never been improved upon, and which enables us
to use fractions with the same facility as whole numbers, thereby
immensely increasing the power of arithmetic. A full explanation of
the notation is given in sections 4, 5, and 47, but the following extract,
translated from ' Rabdologiae,' Bk. I. chap, iv., is interesting as being
his first published reference to the subject, though the above sections
from the Constructio must have been written long before that date, and
the point had actually been made use of in the Canon of Logarithms
printed at the end of Wright's translation of the Descriptio in 1616.
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