LOGARITHMS—D OCAGNRE. 179 
It would take much too long to pass in review the editions of 
tables of logarithms published in various countries during the last 
three centuries; the number certainly exceeds 500.! 
As to France, it must not be forgotten that Napier’s book, intro- 
duced into our country by Henrion, was republished in Lyon in 1620. 
What are known as “‘common”’ logarithms, were brought into France 
by the Englishman Wingate, who likewise contributed to popular- 
izing the slide rule. 
Some tables in seven decimals, by Gardiner, were in 1770, issued 
in an elaborate edition at Avignon though the work was quite un- 
manageable on account of its folio form. On the completion of these, 
Callet reproduced them in 1785, in a volume of convenient size, the 
execution of which does honor to the capable printer Ambroise Didot. 
At the time of a new edition of this work, in 1795, Firmin Didot, 
son of Ambroise, invented the stereotype, which has the great ad- 
vantage of permitting the correction of mistakes as soon as they 
are recognized without running the risk of introducing new ones. 
No work on logarithms not based on the prototype of Vlacq, was 
published before the end of the eighteenth century when the adop- 
tion in France of the metric system, entailing the centesimal division 
of the quadrant, required the calculation of new trigonometric tables. 
The direction of this important work was unfortunately given to 
Prony who organized it in a truly remarkable way. Having confided 
the choice of methods and the establishment of formulas to several 
mathematicians of whom the best known was the illustrious Legendre, 
and having entrusted the determination of results which may be 
called primary, to professional calculators, he gave the task of filling 
the rest of the columns beyond these primary results to assistants 
who, in the domain of calculation, could be regarded only as ordi- 
nary workmen apt merely in performing additions required by the 
use, directed by the professionals, of the method of differences. It 
is curious to note that the majority of these assistants had been 
recruited from among the hair-dressers whom the abandonment of 
the powdered wig in men’s fashion had deprived of a livelihood. It 
goes without saying that in view of the control of the results (carried 
out to the fourteenth decimal), all these calculations were done in 
duplicate in localities distant from one another. 
These tables of Prony, called also “du cadastre,”’ of which the 
publication, cut by Didot to 12 decimals, was interrupted for the 
time by the failure of the assignats, gave birth, several years ago, to 
the eight-decimal tables of the geographical service of the Army, 
executed by the National Printery with type specially cast for the 
1 Details concerning the most important publications are given in the article, “Numerical calculations” 
in the French edition of the Encyclopedia of Mathematical Sciences (Gauthier-Villars, 1909), which the 
author of the present article signed with Prof. R. Mehmkede, Stuttgart. 
