i8 95 . THE CANONS OF SOUTHERN FRANCE. 381 



Readers who wish for further particulars about this curious 

 country will find excellent descriptions in the readable book by Mr. 

 Baring-Gould ; and so far as its physical features are concerned, in 

 E. A. Martel's marvellously cheap and beautifully illustrated volume 

 on the Cevennes. 2 My present intention is to discuss a point on 

 which both these writers seem to be behind the knowledge of the day 

 — namely, the manner in which these wonderful ravines have been 

 formed. 



Mr. Martel argues, and Mr. Gould takes it for granted, that 

 the canons were originally subterranean watercourses, and that the 

 caverns formed by these underground waters became open valleys 

 by the falling in of their roofs. This idea has commended 

 itself to other travellers, and is even shared by some who have a 

 considerable knowledge of geological causes. It is a possible explana- 

 tion, and looking to the canons alone, without considering the 

 valleys beyond and below them, it might seem a reasonable way of 

 accounting for their existence ; but it is not the way in which other 

 gorges and canons have been formed, and there is no reason that I 

 can learn why these should have been formed in so exceptional a 

 manner. 



A few decades ago it was generally supposed that such deep 

 ravines were simply cracks in the earth's crust, and travellers 

 described them as resulting from some " great convulsion of nature," 

 laying stress on the fact that every concavity on one side was opposed 

 by a convexity or promontory on the other, and taking it for granted 

 that the two walls had originally fitted into one another and had 

 simply gaped apart. Now we believe that a river is not there 

 because of the valley, but the valley is there because of the river, 

 which has gradually cut and carved its way through the solid land, 

 and has thus led to the formation of the valley. 



Let us grant, therefore, that running water has made the canons 

 of Lozere; but did the water begin its work below, or did it cut its 

 way down from the surface ? That is the question at issue. Lime- 

 stone formations are always full of fissures, caves, and caverns which 

 have evidently been occupied and enlarged by subterranean streams. 

 If the roof of such a cavern fell in, would it not present the features of 

 a canon ? It is quite possible that it would, in many respects; but it 

 is exceedingly unlikely that the roof of a deep-seated cavern should fall 

 in completely for any great distance. 



The canons are in some places over 1,500 feet deep, and that of 

 the Tarn is thirty miles long ; and one would not expect the roof of a 

 cavern of such a length and such a depth to fall in along the whole 

 of its course. Again, the floor of the canon is a continuous slope, 

 while most of the caverns have very irregular floors, here descending 

 with a vertical fall, there blocked by a barrier which forms a lake. 

 The roof is as irregular as the floor, being sometimes low and some- 

 2 " Les Cevennes," par E. A. Martel. Paris, 5th edition, 1894. 



