26 
M. Humboldt on Isothermal Lines^ 
along the coast ; but no attempt has been made to reduce to nu- 
merical expressions the ratios between the seasons in the inte- 
rior and on the coast. In order to do this, I have chosen eight 
places, some of which lie under the same geographic parallels, 
and others in the prolongation of the same isothermal line. I 
h^vve compared the temperatures of winter, of summer, and of 
the waritiest months ; for a summer of uniform heat excites less 
the force of vegetation, than a great heat, preceded by a cold sea- 
son. The terms of comparison have been along the Atlantic ; 
the coasts of Brittany, (from St Malo and St Brieux to Vannes 
and Nantes) ; the sands of Olonne ; the Isle of Oleron ; the 
embouchure of the Garonne and Dax, in the department of the 
Landes; and in the interior, corresponding to the same parallel, 
Chalons sur Marne, Paris, Chartres, Troyes, Poitiers, and 
Montauban. Farther south, from 44^° of Lat. the comparisons 
become incorrect, because France, locked between the Ocean 
and the Mediterranean, presents, along this last basin, in the 
fine region of the olives, a system of climate of a particular 
kind, and very different from that of the western coast. 
Places in the Interior. 
Lati- 
tude. 
Mean Temperature 
Of 
the Year. 
Of 
Winter. 
Of 
Summer. 
Of the 
Warmest 
Month. 
Fahr. 
Fahr. 
Fahr. 
Fahr. 
Chalons sur Marne, - 
48°. 57 
50°.5 
36°. 1 
60°.6 
67°. 5 
Paris, 
48.50 
51.1 
38.7 
65.3 
67.5 
Chartres, 
48.26 
50.7 
37.0 
64.6 
65.7 
Troyes, 
48.18 
52.2 
38.3 
67.3 
68.4 
Chinon, 
47.26 
53.4 
38.7 
69-1 
'70.2 
Poitiers, 
46.39 
54.3 
39.7 
67.1 
69.3 
Vienne, 
45.31 
55.0 
38. 7 
71.6 
73.4 
Montauban, 
44.01 
55.6 
42.6 
, . 69.3 
71.4 
Places on the Coast. 
St Malo, 
48°. 39' 
55°. 5 
42°.4 
66°. 9 
07".5 
St Brieux, 
48.31 
52.3 
41.7 
64.4 
67.1 
Vannes, 
47.39 
51.8 
39.7 
64.4 
65.8 
Nantes, 
47.13 
54.7 
40.5 
68.5 
70.5 
La Rochelle, 
46.14 
53.1 
40.3 
66.6 
67.1 
Olei-on, 
45.56 
58.1 
41.6 
68.5 
72.1 
Bourdeaux, 
44.50 
56.5 
42.1 
70.9 
71.4 
Dax, _ . 
43.52 
54.1 
44.4 
67.3 
68.9 
