106 PEOCEEDINGS 03? THE GEOLOGICAL SOCIETY. 



character, with those of other rivers, of which I have had surveys 

 made ; and I hoped to have brought the whole subject of valley-gravels 

 before the Society in the early part of 1868. The announcement of 

 the intended absence fi^om England of llr. Prestwich has induced me 

 to describe the Amiens gravels first, in order to have the advantage 

 of his presence at the meeting, reserving my account of other river- 

 gravels and general comparison to a future paper. 



The plan and sections of the Quaternary deposits at Amiens illus- 

 trating this paper will, I hope, make the actual geographical and 

 geological positions of the Amiens beds quite clear. 



It should be mentioned that, in August 1866, after examining the 

 levels myself, I called at the railway office at Amiens to obtain the 

 precise height of the different points on the railway above the sea, 

 and to get the name of a competent surveyor, and was referred to 

 the chief engineer, M. Guillom. That gentleman only saw me for a 

 few minutes, but kindly promised that if all the points on which 

 I required information were laid down on a plan, he would have the 

 sections carefully taken for me in a few weeks. This plan was ac- 

 cordingly sent to him by me a few days afterwards, with the lines 

 marked on which I wished the levels. 



The work was more tedious than was expected by M. Guillom, 

 and he did not send me the measured sections until May 1867. The 

 levels of these sections have been taken with the greatest care, and, 

 I believe, are as precise as any that have been taken for geological 

 purposes ; and I am therefore indebted to M. Guillom for the means 

 of drawing an exact picture of the surface of the chalk prior, as I 

 believe, to the deposition of any of the valley-gravel or loess at 

 Amiens. The value of this communication therefore much depends 

 on M. Guillom' s survey. 



The heights on the maps and sections are in English feet, the datum 

 line being mean tide at Havre. The scale of the plan (Plate III.) is 

 31 inches to a mile. The vertical scale in Plate lY. is ^ inch to 

 55 feet, and is three times the horizontal scale. The dotted lines on 

 the plan show the position of five sections, I K, E S, L M, IN" P, 

 N Q, nearly at right angles to the river, some of them extending 

 to a height of 200 feet above the sea. The line A B is along the 

 Imperial Road. See Plates III. and IV. 



II. Desceiption oe the Longitudinal Sechok-. 



There is also a longitudinal section, divided into three parts on ac- 

 count of the pubKe buildings at St. Acheul preventing continuous 

 levels being taken. The divisions are C D, E F, and G H ; but it 

 will be treated sometimes in this paper as one section, C H. See 

 Plate lY. figs. 3, 4, and 5. 



It passes through the celebrated pits of St. Acheul. and is bounded 

 by the River Arve, a tributary of the Somme, at its eastern point, C, 

 and by the escarpment of chalk in the Eue de Cagny (700 yards 

 west of the railway-station, Amiens) at its western extremity, 

 point H. 



