Contenu du sommaire

Residential mobility is not yet a well known phenomenon ; it cannot be measured easily and census are mostly useless on this point. Could the analysis of elector's migrations give us a better information on this subject ? In testing the method on the example of the second arrondissement, in the center of greater Lyons, the study attempts to measure what contribution can be expected from such an analysis for a better knowledge of residential mobility. It tries to determinate the limits and the weaknesses inherent to the results. The pattern of migrations described for Lyons, suggests some hypothesis that must be checked and precised by other ways and on a different scale.

Through a detailed study of the Pliocene Outcrops in the St-Péray valley we can identify, owing to their recurrent position beneath granitic slopes and also to their sinuous lay-out on a map, and old prepliocene riverbed of the Rhône from St-Péray up north down south to St-Georges-les-Bains. Besides, numerous outcroppings of rhodanian pebbles show that the river once again took that bed during the Villafranchian then the Giinz periods, heaping up during the latter a powerful, 40 meter high accumulation-sheet, prior to giving up that valley entirely while it was being hollowed out and the western river branch first met, further down south, the Charmes granitic threshold. The St-Péray depression thus became a two levelled dead valley of the Rhône : the higher one reaching up to 195-200 m and, the lower one to 170-180 m, both deeply weathered during the interglacial Günz-Mindel period (paleosoil ≥ 4-5 m) ravined and fossilized during the Mindel by siliceous local alluvia on the western side (Massif Central), by calcareous ones on the eastern (Crussol's Hill).

The weight of the district of St-Etienne on the French cycle industry has been quite lessening since 1938. The scooter-market as well as the moped and the motorcycle market have been missed. The American « bike-boom » is cautiously welcome. The productive structures and the managers' mentality are still deeply rooted in craftsmanship. But fort all that, this district secures nearly 40 % of the spare-parts producers turnover, and relies on a small number of leading firms.