INTRODUCTION 9 



able-bodied men to defend its frontier, and the crowd 

 that still returns to these pleasant gardens, to rest 

 among beds of flowers and pools of water, is made sombre 

 by the ever-present marks of mourning. Yet the chil- 

 dren, who must carry on the great traditions of France 

 after the war has ended, mercifully spared the depression 

 which their elders so bravely conceal, sail their boats 

 across the pond as in happier days. A string orchestra, 

 with many women now among its musicians, draws a 

 group about it beneath the trees. In spite of the war 

 the old life of Paris still goes on. 



Encircling the pool, and stretching away on all sides, 

 the busts and statues of eminent men look out of the 

 past. Even the light reflected from the windows of the 

 palace tells of great discoveries. For on a winter's day 

 in 1808, while looking at one of these windows through 

 a piece of Iceland spar, Malus detected for the first time 

 that remarkable property of light --its polarization by 

 reflection which aided greatly in the establishment of 

 the wave theory by Fresnel. 



To our left rises the great dome of the Pantheon, 

 inscribed " Aux grands hommes la patrie reconnaissante," 

 enshrining the tombs of Hugo, Lagrange, and Bougain- 

 ville, and testifying, in the mural decorations of Puvis 

 de Chavannes and in Rodin's "Le Penseur," to the 

 perennial flow of French genius. Here, in 1851, Foucault 

 suspended from the lantern of the dome an immense 

 pendulum which, swinging in an unchanging plane as 

 the floor turned beneath it, made visible the rotation 

 of the earth. Close at hand stands the Bibliotheque de 

 Sainte-Genevieve, with its rich collection of manuscripts 

 and early printed books; flanked by the Ecole de Droit, 

 fronting on the broad Rue SoufHot. Book shops are 

 everywhere, devoted to law or to medicine, to history, 

 art or science, to theology or belles-lettres. On all sides 



