NAPIER COMMEMORATIVE LECTURE. 65 
returns to the same topic in the dedication of the Rabdologia 
of 1617, an Hnglish translation of which reads as follows:— 
“The difficulty and prolixity of calculation (most illustrious 
Sir), the weariness of which is so apt to deter from the study of 
mathematics, I have always, with what powers and little genius 
I possess, laboured to eradicate. And with that end in view, I 
published of late years the Canon of Logarithms, wrought out by 
myself a long time ago, which, casting aside the natural numbers, 
and the more difficult operations performed by them, substitutes 
in their place others affording the same results, by means of easy 
additions, subtractions, bisections, and trisections. Of which 
logarithms, indeed, I have now found out another species much 
superior to the former, and intend, if God shall grant me longer 
life, and the possession of health, to make known the method of 
constructing, as well as the manner of using them. But the 
actual computation of this new Canon, I have left, on account of 
the infirmity of my bodily health, to those versant in such studies; 
and especially to that truly most learned man, Henry Briggs, 
Public Professor of Geometry in London, my most beloved friend.” 
The change referred to in those passages practically 
amounts to a choice of a base for the logarithms: and in 
our modern notation, the choice between which Napier 
and Briggs hesitate, is between 10 and 1/10 for the base. 
After his death at the age of 67, in the same year as the 
publication of the Rabdologia, the Mirifici Logarithmorum 
Canonis Constructio was published by the care of his son 
in 1619. From this work we have already quoted frequently 
in the preceding account of Napier’s discovery. It had 
L been written several years before the publication of the 
Descriptio, but the author had delayed publishing it “until 
he had ascertained the opinion and criticism on the canon 
of those who are versed in this kind of learning.’’’ 
In the Constructio, Napier uses the term artificial num- 
bers, for what he calls logarithms, in the Descriptio; and 
* See Introduction to the Constructio by Robert Napier. 
E—May 21, 1914. 
