side by cliffs of hard
limestone, 30 to 40 metres high, in which innumerable caves are
scooped--the so-called _boves_, which are used as dwellings, with doors
and windows flush with the face of the cliff. These _boves_ are
invaluable defensive positions, out of reach of bullets and shells. The
valley bottom is wet and swampy, with dense clumps of poplars mingled
with alder-bushes. There are numerous villages at the foot of the
cliffs,--Rozet-St.-Albain, Breny, Armentieres,--or on the slopes above,
like Noroy. A frontal attack on such a position would have been too
costly. The Allies turned the line of the Ourcq from the north. They
crossed the river in force in the upper part of its course, where it
has not yet attacked the stratum of hard limestone, and where the valley
is wider, and the sides are less steep. Nevertheless they encountered
terrible difficulties.

[Sidenote: Strategic value of hills of Orxois.]

North of the Ourcq, indeed, the last heights of the Orxois form another
chain of hills, from four to six kilometres wide--the last obstacle
before we come to the plateau of the Soissonnais. These hills are of the
greatest possible diversity of shape and vary in height from 200 metres
at the western extremity to 230 at the eastern. Their bases consist
largely of sandstone and Fontainebleau sand, with clumps of forest
scattered here and there; higher up is the softer limestone, the land
being entirely cleared and covered with crops. Here and there we find
the remains of the former covering of clay and Fontainebleau
sand--wooded ridges which expand toward the east into the wood of
Seringes, the forest of Nesle, and Meuniere wood. These hills, the last
as we travel northward, where they command the whole of the Soissonnais,
have therefore the greatest strategic value, particularly the positions
of Hartennes, Plessier-Huleu, and Seringes.

[Sidenote: The French approach from the west.]

Luckily these formidable defensive positions were approached from the
west, astride the ridges. Starting from the forest of Retz, the French
crossed the Savieres with a rush, and in a single bound reached
Noroy-sur-Ourcq and Villers-Helon, which lie along one of the ridges,
surrounded by orchards. On July 19 they had advanced three kilometres to
the east; the strong line of the Ourcq was outflanked. On the 20th they
were at Parcy-Tigny and Rozet-St.-Albain, pushing forward over the
broken ground planted with sugar-beets and cereal