308 



Mount Jura. 



I)Ale not so 

 high as Recu- 



Reculet. 



Temperature 

 of springs. 



Agrees \»Uh 

 Saussure's law 



Another does 

 not. 



GEOLOGICAL OBSERVATIONS IN FRANCE. 



The Jnra ig a chain of calcareous mountains 15O or 200 

 miles long:, by 35 or 40 broad ; running S. S. W. and N N. E,. 

 from the neighbourhood of Poii^iu in Eresse to Basil. Its 

 course therefore is nearly parallel with that of the Alp§, of 

 ide external chains of which it must be considered as a de* 

 pendance. It is not very easy to mark the Ssituation and 

 form of the strata of the Jura. ]\Jr. Saussure thinks, .thai- 

 the strata of the eastern chain, which \^,t\ie JQftiest arid the 

 nearest the Alps, rise leaning against the centre of the chain, 

 and decline on the opposite side; vvliile the strata of the lol- 

 lowiug chains to the west have the form of arches, or semi- 

 -arches, and terminate in plains, the l^ase of which consists 

 of horizontal Ji>eds of limestone. 



The Dole, twelve miles north of Geneva, has been gee 

 nerally deemed the highest summit of the Jura. Accord- 

 ing to Mr. Deluc it is 658 toises above-the lake, a«d copse* 

 quently 847 above the sea. I co|isideF the Reculet, ten 

 miles north-west of Gerieva, as rath eF higher. It is one oi 

 the number of mountains in Ihe chain, that appear to con- 

 tradict the general for m, of, th^ strata above given; for, iri-. 

 stead of rising against the/centre of the chain, they present' 

 their cliffs to the Alps. - ., .-w.'-ii: u».' ; 



In an expursjoii I made on the Re(cu.let,,the 7th of 4"- 

 ^ust, 1802^ 1 5 J^scertaii^ed; th^ tejaiperature ofivvo; springs 

 at the same time with their,hei^ht .^bo\e. tl},e sea. The tem- 

 perature x)f one, situate above the chalet of Arderau, and 

 730 toises above the sea, was 48° [43° F.], while that of 

 the open air was 21-5° [80-3 F.]. That of the other, called 

 ^oqverse, 815 toises above the sea, was 4° [41° F.], the 

 thermometer in the open air bting at 20*5° [78° F.]. These 

 twp. observations agree sufficiently with the law of the de- 

 crease of heat laid do^n by Mr., Saussure ;^ the following is 

 pot quite so consistent with it. Oa the 29th of August, 

 X^Q2, .the thermometer ip a fine spring near the village of 

 V^irisf at the foot of .mount Saleve, 200 toises above the 

 sea, stood at 8*5° [51-2^ F.], and in the open air at 13*7® 

 ^62-8°F.]. 



XII. 



