THE CONE OF THE TINIERE. 317 



cone has been bisected for a length of one thousand feet, and 

 to a depth, in the central part, of about thirty-two feet six 

 inches above the level of the railway. The section of the cone 

 thus obtained shows a very regular structure, which proves 

 that its formation was gradual. It is composed of the same 

 materials (sand, gravel, and larger blocks) as those which are 

 even now brought down by the stream. The amount of detritus 

 does, indeed, differ slightly from year to year, but in the long 

 run the differences compensate for one another, so that when 

 considering long periods, and the structure of the whole mass, 

 the influences of the temporary variations, which arise from 

 meteorological causes, altogether disappear, and need not 

 therefore be taken into account. Documents preserved in 

 the archives of Villeneuve show that in the year 1710 the 

 stream was dammed up, and its course a little altered, which 

 makes the present cone slightly irregular. That the change 

 wat not of any great antiquity is also shown by the fact that 

 on the side where the cone was protected by the dykes, the 

 vegetable soil, where it has been affected by cultivation, does 

 not exceed two to three inches in thickness. On the side 

 thus protected by the dykes the railway cutting has exposed 

 three layers of vegetable soil, each of which must, at one 

 time, have formed the surface of the cone. They are regu- 

 larly intercalated among the gravel, and exactly parallel to 

 one another, as well as to the present surface of the cone, 

 which itself follows a very regular curve. The first of these 

 ancient surfaces was followed on the south side of the cone, 

 over a surface of 15,000 square feet : it had a thickness of 

 four to six inches, and occurred at a depth of about four feet 

 (1.14 metre measured to the base of the layer) below the 

 present surface of the cone. This layer, which belonged to 

 the Roman period, contained tiles and a Roman coin. 



The second layer was followed over a surface of 25,000 

 square feet ; it was six inches in thickness, and lay at a depth 



