1 IN THE MONOGRAPH SERIES directed by Henri Villat, several fasci- cules
have been devoted to Relativity. First there are the general
presentations ofTh. De Donder (nos. 8, 14, 43, 58), and then those more
specifically devoted to Einsteinian gravitation - notably Georges
Darmois's contribution (no. 25) and that of J. Haag (no. 46) on the
Schwarzschild problem. The present fascicule takes its place alongside
the two latter monographs, but it has been conceived and composed in
such a way that it may be read and understood by anyone with a knowledge
of the principles of Absolute Differential Calculus and of Relativity -
either from the original exposi- tions of Einstein, Weyl, or Eddington,
or, in French, from Cartan's excel- 2 lent works (for everything having
to do with mathematical theories) and 3 from Chazy's (for Relativity and
Celestial Mechanics), or naturally from Levi-Civita's The Absolute
Differential Calculus (first edition, London and Glasgow, Blackie and
Son, 1927) where the two original papers written in Italian are brought
together: namely, Calcolo differenziale assoluto and Fondamenti di
meccanica relativistica (Bologna, Zanichelli). As for the present
fascicule, it is hardly necessary to point out that, as its title
indicates, we seek to establish in the simplest possible terms the rela-
tivistic aspect of what Newton and those who followed him regarded as
the key to ordinary Celestial Mechanics.
