286 J. PARKER ON THE nELATIONSIIll' BETWEEN William Charles Lucy, Esq., F.G.S. j John Grant, Esq. j Colonel J. J. Gibb j Charles Salisbury, Esq., B.A. The following Paper was read r-e- ON TilE RELATIONSHIP BETWEEN THE SOM!IE RIVER AND THE SOM)IE VALLEY. By JAMES PARKER, Esq., F.G.S., Hon. Fe!. Ash. Soc. The subject to which it is my purpose to draw attention in this Paper is the relationship of the Somme River to the valley which bears its name. Much has been written about the lithological character of the sand and gravel beds which appear on the slopes of this valley, and about the organic remains discovered in their midst; and much discussion has taken place as to the analogies existingbetween these beds.jmd those, to all appearance, deposited under similar circumstances elsewhere in France, as well as in our own country. But while these details have received so much attention, it seems to me that the far greater question, namely, how they came to be 'distributed in the positions in which we DId them j-that is, why some are on the surface of the plateau, some in the hollows of the combes, some at the bottom of the valleys, while others are on the sloping sides of the same valleys-has not received the attention it deserves, or, rather, obtained the answer it requires before any conclusion can be drawn from the minor con­ siderations of the lithological character, or the organic remains of the beds in question. It has been assumed that the River Somme deposited them there, and that, therefore, no further questions need be asked on this head. But this assumption involves another, namely, that the river having deposited the gravels, cut a valley through them; or, rather (what this assumption practically comes to), that the River Somme made the valley which we now see. As a necessary consequence, too, it must be assumed that the tributary streams made the' tributary valleys; and, in a word/ that the present contours of the country are wholly due to river, or similar snbaii.iel action. It is my purpose, then, to examine the basil> of these assump­ tions, I propose to ask, and to supply an answer to the question, THE SOMME RIVER A~D THE SOMME VALLEY. 287 whether the River Somme can have, in any sense which may be applied to the words, made the Somme Valley. This lies at th e root of the other questi ons which follow from it. If it cannot have made the vaIley, we have a strong apriori argument at least that it could not have deposited the gravels high up on the slopes, or cut through th em afterwards. And in treating the subject I propose to follow a line of argument, and to introduce considerations which have not, as far as I have observed, been treated by writers on the Somme Valley. I propose to ask your attention to the river as a whole, and the district as a whole, as this seems to me to be not only th e natural order of proceeding, but also, as I venture to say, in this particular instance, the only right way of treating the subject. The district to which I have to call attention is, speaking generally, the ancient province of Picardy, traversed by the River Somme from east to west. So much of it as belongs to the con­ sideration of the question at issue is shown in the accompanying map. It will be seen that this map includes the whole of the water-shed of the Somme, together with that of some six or seven.minor rivers, not tributaries of,_but supplementary to, the Somme. In a word, th e map shows the Basin of the Somme j and in order to bring this point prominently forward, a series of figures vrepresenting, in English feet, the heights of the more promin ent elevations in each district are given on the map; on comparing them a general rise will be seen to exist from the centre towards both the northern cdge and the southern edge. Also a rise (but not so great a one) towards the eastern end. The western side is open to the sea, and though high hills oecur reaching to the water's edge, where in many places along the shore they appear as cliffs, still the average level, especially as the mouth of the Somme is reached, shows a considerabl e, though very gredual, fall from the eastern end. The general idea would be represented by cutting a very shallow spoon across the middle, the upper end near the handl e repr esent­ ing the ground whence the highest tributary stream of the Somme rises. Along the most depressed part the trunk-stream of the Somme flows, but it does not drain the whole. Two or three streams run parallel with it (but independently of it), on the north side, and two or three also on th e south side. On the north we have the Canche flowing out at Etaples, the 288 J. P ARK ER ON T HE llELATIOXSIlT P DEnVEES Authie flowing into the bay of that name. Th en a small drainago stream scarcely t o be reckoned. Then the Somme it self flowing past St. Valery, into a much larger bay than that of the Authio, South of this will be found the Bresle, reaching the sea at Treport, the Y eres near to Cri el and th e Aulne and Bethune, h aving united th emselves together, finally discharg ing th emselves into the sea at Dieppe, While the trnnk streams flow more or less in a straight line towards tbe sea, at the head of most, and more especially at the he ad of the Somme, are a series of ramifying streams. I n the la tter case they join the trunk j ust above Amiens. In the case of the Authie just above Doullens, of" the Bethune just above Neufcha tel. The tributaries which discharge th eir waters into the trunk streams, it will be obser ved, flow in a general sense at right angles to th ose streams. There is no tendency whatever to deflection in a west erly dir ection, such as one would suppose, had they owed their origin to any great flow of water from th e east. When they bifurcate or ramify, th ey do so, on the whole, very evenly, in re­ lation to their ge neral downward cour se. I only briefly touch upon th ese points in this g eneral description of t he map, as th ey will necessarily be referred to again when I come to th e argum ent. Before, however, quitting the general description of tbe map , I should add that it may be relied upon for the accuracy of the general lines of the rivers and their branches, as it is a reduction of th e French Ordnance Survey, to one fourth the scale. That is, each English inch on th e redu ced map repr esents as nearl y as possible five miles.v !,he dist rict here given is comprised in sheets No.6, 7, and 8,11, 12, and 13, 20, 21, and 22, in all nine sheets of that Survey. It will be observed that small portions at th e N.W. and S.W. corners, beyond Montreuil and Dieppe are unavoidably omitted. In order to . bring more clearly into view the course of the rivers, I have omitted all the lines of roads, and communal boundaries, and of canals and railroads, which tend to confuse a map, when used for th e purpose of studying the physical features only. Al so the name s of places are omitted (with the exception of very few, which are retained for th e sake of speedy reference to • The French Ordnance Sur vey is sooloo consequentl y the scale is not so lar ge as the one-inch-to 8. mile -scale of our own Ordnance Map. The map I have giv en is 3~ 0, which will be found to be one inch t o about 0'05 mi les. THE SOllME RI VER AND THE s m l ME VALLEY. 289 the district, should any reader care to compare this map with others) . It was impossible to follow, on the reduced scale, all th e lines of hill-shading represented on the larger scale, and even in that case the numerous undula tions are only very incompletely shown, or rather, only th e chief contours are taken notice of. In th e present map then, the brown hill- shading must be accepted as exhibiting only the more important conto urs, and then only approximately. While the shading tends to give a general idea of the country, I do not think it can in any way suggest any false notions. It remains to add that the red figures represent approximat ely'" the heights of the points above the mean sea level, in English feet. They are selected from a much more extensive series, the highest in any one spot always being chosen. Consequently they do not by themselves afford data for computation of the average height of the hills in that part. Still, by taking the highest in any one district, and comparing it with those in anoth er, a general, and not often inaccurate, idea can be gained of the relation which the heights of the hill s bear to each other in the two distri cts.