76 Notices of Memoirs — Prof. Hebert — Folds of the Chalk. 
folds in the Chalk of Northern France, running in a general direction 
from S.E. to N.W. These folds, five in n umher, he distinguished as 
the axes of Perche, the Seine, Bray, Bresle, and Artois. 1 These are 
crossed almost at right angles by a second set, also nearly parallel, 
whose general direction is consequently about S.W. — N.E. To 
describe this second series, andtoadvance some general views on the 
probable age of the folds in both, is M. Hebert’s object in the paper 
under consideration. 
The first fold of this second series Starts at Rouen, and runs in a 
straight line through Aumale to Pecquigny, whence it is prolonged 
in a N.E. direction, passing a little to the south of Arras towards 
Douai and Tournay. 
The second brings the Glauconitic Chalk to the surface at Pres- 
sagny l’Orgueilleux and La Madeleine, near Yernon, and passes in 
its north-east extension close to Breteuil (Oise), cutting the axis of 
Bray a little to the south of Ville-en-Bray. If prolonged in a South- 
west direction, it would pass between Evreux and Conclies by the 
important fault which has determined the outcrop of the Glauconitic 
Chalk in the valley of the Iton. 
The third fold runs along near the shores of the Channel. Start- 
ing from Petreval, near Fecamp, it extends with a curve, or bend, to 
Dieppe, where it is probably represented by the fault described in a 
previous paper. 2 At both Fecamp and Dieppe the beds dip at a 
higher angle on the N.W. than on the S.E. side. Supposing it to 
continue in the same direction on leaving Dieppe, it would then pass 
through Beaurainville, north-west of Hesdin, intersect the axis of 
Artois at Fruges, and terminate at Dennebroeucq, where the 
Devonian beds crop up. 
The presence of these several folds leads the author to conclude, 
in Opposition to several eminent English geologists, that one, if not 
more such folds exist in the bed of the Channel, which will öfter 
serious obstacles to the construction of a tunnel in the Chalk as 
proposed. That such undulations do exist there, he considers to 
have been conclusively proved by the soundings conducted by 
MM. Potier and De Lapparent. One of these (the fourth of this 
series) would be nearer to the English than the French shore, but 
parallel to the Sandgatte coast, and consequently to the other three. 
The fifth and last of the series is also the southemmost. Com- 
mencing at Ferte-Bernard, it Stretches in a N.E. direction, past 
Beynes to Compiegne, and is exactly parallel to that between Yernon 
and Breteuil. 
Respecting the ages of the folds of both the S.E.-N.W. and S.W.- 
N.E. series, M. Hebert comes to the following conclusions : — 
1. The first, or oldest, is the synclinal fold, in which the Wealden 
1 The correspondence of some of these axes with others on this side of the Channel 
had already been pointed out by M. Ch. Barrois in a communication read before the 
same Society in March, 1875. Thus the axis of Artois is probably represented by 
that of Kingsclere; the axis of Bresle by that of Winchester; and the axis of 
Bray by that of the Isles of Wight and Purbeck. 
2 Bull. Soc. Geol. de France, 2 e Serie, tom. xxix. p. 586, and ibid. 3 e sdrie, tom. 
iii. p. 526. 
