NODULES OF LAVA IN CLINKSTONE. 381 



VIII. 



On the Nodules of Lava found in the Klingstein of the Rock 

 of Sanadoire % 



A HE rock of Sanadoire having been described by various Nodules of lai* 

 naturalists f, we shall confine ourselves to the mentioning of jlj^® phono- 

 a fact, which had long escaped the notice of those whodoire. 

 visited this singular rock, that of nodules of tumefied lava 

 imbedded in the clinkstone. This fact was first observed by- 

 Mr. Lacoste in 1804 + ; and it has been since noticed by 

 Messrs. Menard and Alluaud in the summer of 1807. Hav- 

 ing accompanied these gentlemen in their visits to the Mont- 

 d'Or, we shall point out the road we pursued, and the pre- 

 cise places where this fact occurs. 



1. Proceeding from the lake of GueVi to the rocks of Sa- Places where 

 nadoire and Thuiliere, by the road from Mont-d'Or to itoccurs - 

 Rochefort, and beginning to descend toward the valley, 



where these two rocks are situate, so as to see their summit; 

 on the left of the road, and not above thirty yards from it, 

 is a small eminence, or inequality of the ground, formed of 

 masses and fragments of phonolite, in which nodules of 

 lava are imbedded. 



2. On ascending the great slope at the base of Sanadoire, 

 which is on the west, and directly opposite Thuiliere, we 

 find similar nodules in the crumbled materials from above, 

 which are all of phonolite. Some of these nodules scarcely 

 adhere to the mass that includes them, and are separable by 

 a single stroke of a hammpr. Others adhere £o it more 

 closely, but still do not form one continuous substance with 

 it. The surface of those separated by the hammer is round- 

 ed, but irregular, smooth, and covered with a slight shining 

 coat, which appears to be a very thin pellicle of klingstein. 



These nodules are of different kinds of lava. The lava of dif- 



A, A black, compact lava exhibiting in its fracture aj Gre ^ j inds * 



* Journal de Physique, vol. Ixvii, p. 54. 



f Memoirs of the French Academy, for 1771 and 1773 ; Desma- 

 rets, Memoire sur le Basalte. Journ. de Phys. tome 59, an 1804. 

 JDaubuisson. Memoire sur la Phonolithe. 



X Lacoste's Geological Letters, a work in which they who visit 

 Auvergne will meet with facts no where else described. 



multitude 



