NATURE 



377 



THURSDAY, MARCH 14, 1872 



LA SEINE* 



IN carrying out the great works for the improvement 

 and embellishment of Paris under the late Empire, 

 all incidental discoveries of objects relating to art, history, 

 and science, were systematically investigated, recorded, 

 and preserved, instead of being left to the chance and 

 uncertain description of casual and independent ob- 

 servers. In a liberal and enlightened spirit the Munici- 

 pality of Paris and the Pr(^fet of the Seine (M. Hauss- 

 mann) established a proper organisation and a staff 

 {Service des fouilles et des substructions) to follow up such 

 discoveries, to take plans of old works, to preserve all art 

 treasures or objects of scientific value ; to note, in fact, and 

 to investigate everything of interest. Men eminent in 

 several departments were consulted, and engaged to draw 

 up reports with full illustrations of the discoveries. By 

 these judicious measures, the knowledge of the topo- 

 graphy, antiquities, and archeology of Old Paris has been 

 greatly advanced. Works of the Roman, Gallic, and 

 Mediaeval periods have been brought to light, surveys and 

 plans made, and the more important specimens preserved 

 in situ or in the public museums. 



To M. Belgrand, the eminent and able engineer for the 

 water supply and drainage of Paris, was deputed the work 

 of recording all the geological and some of the archreo- 

 bgical facts discovered during the construction of the 

 large works on which he was engaged. 



Paris up to the last few years had been supplied with 

 water from local sources (river, canal, and wells), but as 

 these were found insufficient and of indifferent quality, it 

 was determined to seek for other and better sources of 

 supply at a distance, and some large springs in the chilk 

 district, respectively distant sixty and eighty-four miles 

 from Paris, were eventually selected by M. Belgrand, and 

 their waters werebrought to Paris by meansof aqueducts on 

 a high level. In carrying out this great work, M. Belgrand 

 made himself intimately acquainted with the hydrography 

 of the Basin of the Seine. He explored every valley, and 

 determined the regime of every important river. The 

 result of the first part of the inquiry appeared in a valuable 

 series of tables, showing the connection between the 

 rainfall and the discharge of each river — the extent and 

 nature of the tloods, and the geological character of the 

 ground with reference to the range and extent of the 

 permeable and impermeable strata, and which he illus- 

 trated by a specially coloured map. In connection with 

 the construction of the aqueducts, M. Belgrand had also 

 to ascertain the nature of the surface and the contours of 

 the hills and great plains along which he carried them, and 

 to examine the many pits whence the materials for con- 

 struction were obtained. This geological investigation led 

 to the discovery of many interesting specimens, and further 

 suggested many theoretical inquiries relating to the origin 

 of the present surface, and to the regime of the old Seine 

 during the later geological periods. The result of the in- 



' Le Bassiii Parisicit aiix Ages AnUhistori.]ms. P.ir M. Belgrand, 

 Inspecteur-Genc'ral des Poms and Chaussees, Directeur des Eaax et des 

 Egouts de la ViUe de Paris. (Paris : Imprimcrie Imperial.) 



quiry is embodied in the three handsome quarto volumes 

 before us— one of 255 pages of text, with io5 pages of 

 introduction, descriptive of the country and giving the 

 theoretical views ; a second containing plates of fossils, 

 of flint implements, and pit sections ; and a third with 

 extended coloured sections and a monograph by M. Bour- 

 guingnat of the shells found in the Drift beds. 



Paris stands on Tertiary strata, from beneath which, at 

 a distance of some miles, the chalk crops out and forms 

 a belt many miles in width. These formations constitute 

 a table land having a height of 100 to 200 feet alono- the 

 sea coast of Normandy, and rising from 500 to 6do feet 

 inland in Champagne. This district is traversed by the 

 Seine and its tributaries, flowing in comparatively narrow 

 valleys cut deep into the table land ; while, on the extended 

 upland plains thus formed, there rise, here and there 

 ranges of hills of Fontainebleau Sands or other later 

 Tertiary strata. The strike of these hills is in a direc- 

 tion entirely distinct from that of the hill slopes flanking 

 the river valleys and forming part of the present river- 

 system. The latter range in various directions — north, 

 north-east, south, and south-east— in accordance with 

 the direction of the tributaries of the Seine until they 

 join that river, the main chmnel of which has, from 

 Montereau to the sea, a general direction south-east to 

 north-west. M. Belgrand found that the hills on the 

 plains nearly all ranged in this one given direction, or 

 approximately from south- east to north-west, with inter- 

 vening valleys having the same direction. Numerous 

 such ridges, none being of any great length and all narrow 

 and having this definite trend, are found to extend over 

 the whole plateau area uninfluenced by the more tortuous 

 deeper river-valleys which intersect the same area at 

 various angles to their course. The river- valleys are 

 covered with gravel formed of the debris of the rocks 

 through which the present rivers flow, while the plateau 

 valleys and plains are free from such debris, but are 

 covered with a uniform layer of red clay or loam. Whence 

 M. Belgrand concludes that the two systems of valleys 

 have a different origin. He contends that it is not pos- 

 sible to have a true river channel without having more or 

 less drifted gravels formed by the constant action of run- 

 ning water and by floods, and therefore that these higher 

 valleys could not have been formed by river action, while 

 at the same time their rectilinear and special bearing in- 

 dicates that their formation is due to one common and 

 independent cause. 



M. Belgrand considers that the only e.xplanation which 

 will account for the phenomena presented by these 

 higher-level valleys and hills, is the rapid and transient 

 passage of a large body of water over the surface ; and 

 as the excavation of these higher valleys took place after 

 the formation of the Fontainebleau Sands and of the 

 Calcaire dc Beauce (Miocene), and before the Pliocene 

 period (for the Etephas meridionatis of the valley of the 

 Eure shows that the land had then emerged), and as also, 

 according to M. Elie de Beaumont, the elevation of the 

 main chain of the Alps took place at the same period, 

 M. Belgrand connects the two events and supposes that 

 the sea of the Pliocene deposits of the Alpine area was 

 thereby displaced and that it swept over this northern 

 portion of France, denuding the softer portions of the 

 strata and leaving narrow ridges of the harder portions 



