212 GEOLOGICAL OBSERVATIONS IK FRANCE. 



when accurate barometrical measuremeuts are published, to 

 mention the hour of the day when they were made ; and at 

 the same time the measurements of other travellers, liowever 

 diiJerent they may be from our own, with the formulae they 

 employed if possible. Thus useful materials would be stored 

 up for the promotion of science. 



The following observations are classed according to the 

 journies in which they were made; and in them I have coii* 

 formed as much as possible to the rules I have laid down, 



S^ct. L 



Tour through Heights ascertained during a tonr made in the ci-devant prcH 

 Nonnaiidy. vinces of Picardy and Normandy, 



This tour was made toward the end of the summer of 

 1803, in company with my friends and colleagues Messrs^ 

 Its leading ob- Jurine and de la Roche. I set off from Paris with intention 

 jects. ^Q follow tlie seacoast as much as possible, to examine the 



structure of the shores, and the different elevations of the 

 cliffs. I used a siphon barometer made by Diimotier, which 

 however I did not think sufficiently accurate to allow me 

 to consider my results in any other light than, simply geolo- 

 gical. 

 Chalk soil in- It is Well known, that part of the soil of France, pro- 

 terspersed with ceeding in a north-west direction from Champagne to the 

 borders of the sea, is composed of chalk, which continues 

 as far as England, and includes flints of irregular form, se- 

 parate from each other, but arranged in parallel beds, more 

 or less distant, which alternate with the chalk. Beauvais, 

 Amiens, &c., are in this line. On the left banlc of the 

 Somme, below Amiens, ore little hills of no great height 

 formed of this chalk, which is burned for lime. At Pic- 

 quigny there is very good peat. 



At St. Valery on the Somme the cjiff is not above 6o or 

 Stratum of ^^ feet high. The chalk is in ])orizontal strata, a foot and 

 flints, which half thick, between which is a very thin bank of flints, 

 out torm\he The^e flints, separated and rounded by the waves of the sea, 

 pebbles on the appear to compose the pebbles that are found at the mouth 

 of the river. At Crotoy, a town formerly fortified, and 

 built on the right bank of the Somme at its mouth, the cliff 



no 



