LOGARITHMS—D’OCAGNE, 181 
extended, of which the primitive type, conceived in 1652 by Oughtred, 
has since then, with various modifications in detail, multiplied in an 
infinite number of varieties.! 
Combined with diverse mechanical means, such logarithmic 
circles have in their turn brought about the construction of machines 
to accomplish operations of a very different complication; such a 
one is that extraordinary machine for resolving algebraic equations 
of any degree whatever, designed about 20 years ago by M. Torrés- 
Quevedo, and which that ingenious Spanish scholar exhibited several 
months ago, among many other devices of his own invention, not less 
surprising, in the mechanical laboratory of the Sorbonne. 
It is also from the logarithmic scale that Lalanne derived the idea 
of anamorphosis, announced in 1843, which has so notably con- 
tributed to the development of graphic methods of calculation and 
has been the origin of the new conceptions which gradually developed 
into what is to-day known as Nomography. 
When we thus rapidly glance at the great multiplicity of results 
in practice and in theory which have sprung, from the invention of 
the Scotch lord in 1614, we come to realize that of all the achieve- 
ments of human genius, not one has surpassed this in fecundity, and 
we can have only praise for the happy initiative which, as shown by 
the impressive celebration of its tercentenary, has led the public 
thought toward the source of so much progress. 
1 On these methods and the different mechanical or graphic methods which have been devised for the 
simplification of numerical calculation, see the work of the author of the present article: “Le calcul sim- 
plifié par le procédés mécaniques et graphiques”’ (published by Gauthier-Villars). 
