Reviews—A. de Lapparent—COarte géologique de la France. 227 
7. That the band of moving sands, which has been the source of 
the present dunes, was formed after the formation of the drift in the 
Netherlands, and consequently at the latter period of the Glacial 
epoch, or after this period. 
8. That the alluvial deposits of the Netherlands are posterior to 
the formation of the maritime dunes. J. M. 
RAV CWS. 
wee 
J.—MémorrEs POUR SERVIR A L’EXPLICATION DE LA OarTE Gfho- 
LOGIQUE D&TAILLEE DE LA France. Le Pays pe Bray. Par 
A. pr Lapparent, Ingenieur au Corps des Mines. (Paris, 1879.) 
HIS memoir, the result of many years of labour, undertaken for 
the preparation of the Geological Map of France, is descriptive 
of the Pays de Bray, a district (from its peculiar features) of con- 
siderable interest to the geologist. 
The memoir consists of three parts, which treat respectively, 
of the physical features, the succession of geological formations of 
which the region is composed, the elevation of the district, and its 
connexion with other disturbances in the Paris basin. The Pays 
de Bray has long engaged the attention of geologists. Noticed by 
O. d’Halloy in 1818, its structure has been further described by 
Elie de Beaumont, Graves, Passy, Cornuel, Hébert, and Barrois. 
But the study of the district has been beset with much difficulty, for 
the region is covered by woods and pastures, and divided by thick 
hedges and a great number of inclosures of very difficult access. 
With no stone quarries, the geologist can only avail himself of sand- 
pits, or of clay-pits opened for the manufacture of different kinds of 
pottery. However, the improvement of roads, fresh openings of the 
surface, and constructing railways during the last fifteen years or 
more, have materially assisted a better knowledge of the country. 
The railway from Rouen to Amiens traverses the Pays de Bray at 
right angles to its chief elevation, and two others, from Beauvais to 
Gournay, and from Gournay to Neufchatel, follow the longitudinal 
axis, so that the district “so long isolated in the middle of Normandy 
as a sort of quagmire, almost forsaken by observers, is at the present 
time one of those affording valuable results, although the thick 
herbage over a large area still prevents the direct study of the 
subsoil.” 
The Pays de Bray, or Valley of Bray, is not an ordinary valley, 
but, like the English Wealden area, a so-called valley of elevation 
and erosion ; it is an elongated semi-elliptical opening or trapezoidal 
amphitheatre contracted at both ends, extending from St. Vaast on 
the north-west to Tillard south of Beauvais on the south-east; the 
longer axis is about 40 miles, and that of the smaller 30 miles. 
It is not, however, an elevated dome, but its structure is due to a 
rectilinear dislocation, fault or sharp fold, a true line of rupture, 
around which are grouped a number of secondary effects (p. 132). 
A transverse profile of the Pays de Bray shows three principal 
