426 
TJie Water Economy of France 
The western or oceanic division comprises by far the most 
extensive area. It extends over two-thirds of the whole surface 
of P'rance, and consequently drains no less than 88 million 
acres. 
The central group of mountains in Auver<i^nc, so striking^ly 
overtopped by the three great volcanic summits of Mont d'Or, 
Cantal, and Mesenc, send forth from their granitic bases the 
feeders alike of the northei'n basin of the Loire, and the southern 
basin of the Garonne. From the northern declivity, each in its 
own deep and well-defined valley, flow the Loire and the AUier 
on the ncjrthern route ; and from the southern slope the Dordogne 
hastens to pay its tribute to the Garonne. We have also on the 
north side the Cher, the Indre, the Creuse, the Vienne, tributaries 
of the Loire ; from the southern declivity flow the Drome, the 
Isle, and the Vezcre, which fall into the Garonne ; and from the 
point where the granitic and crystalline mass disappears beneath 
the stratified layers from whence it burst forth, the Tarn and 
the Lot spring up to swell the waters of the Garonne. 
Thus Auvergne is the cradle of all the great rivers which dis- 
charge their waters into the Atlantic Ocean, with the exception 
of the Garonne, which, together with its southern tributary, the 
Arriege, is of Pyrenean origin. The Arriege may even be con- 
sidered as a branch of the Garonne rather than a distinct river, 
as it forms with the upper part or torrential stream of that great 
river a huge triangle, the base of which is formed by the highest 
range of the Pyrenees, from Puycerda to Bagneres de Luchon. 
East of that extreme lofty range flow the waters of the river Tet 
towards Pcrpignan, thus forming Avith the other mountain-stream 
the Tech the small western section of the Mediterranean basin, in 
the same manner as the Adour and the drainage-water from the 
western slopes of the Pyrenean range form the extreme southern 
secondary basin of the oceanic division. 
All those tributary streams that belong to the Loire basin, as 
well as those belonging to that of the Garonne, flow through 
secondary strata of the oolite or chalk formation before their con- 
fluence with the main streams into which they merge, which 
flow in tertiary or alluvial strata. 
Below the city of Angers the Loire is joined from the north 
by the Maine, which is itself formed by the confluence of three 
rivers, the Loir, the Sarthe, and the Mayenne. Lower down it 
receives the Vilaiiie, the Aure, and the Blavet, which bring the 
waters from the Breton peninsula. 
Between the mouth of the Loire and that of the Gironde — a 
name given to the stream formed by the junction of the Dor- 
dogne and the Garonne, just below Bordeaux — the space 
intervening is drained by two rivers which empty their waters 
