518 



J. F. BLAKE ON THE UPPER 



This is an exceedingly complicated classification ; but it is neces- 

 sary to give it in full, because points of discussion arise depending 

 on its details. According to the descriptions given by Tombeck, all 

 kinds of extraordinary developments of the Corallian rocks take 

 place in this district, and many differences are observable from any 



thing found elsewhere; but though 

 Fig 5 —Map of Part of the {t ma J seem presumptuous to found 

 Valley of the Bognon. an Y opinion upon a rapid survey, yet 

 (Scale 1 • 80,000.) ^ na ^ surve y? directed to the special 



examination of crucial spots, fails to 



reveal any thing very abnormal, 

 though there are considerable differ- 

 ences when the rocks are compared 

 with those already studied. In point 

 of fact, an examination of the locality 

 fails to comfirm M. Tombeck's con- 

 clusions in several important points. 



The chief point necessary to esta- 

 blish is the true succession of the 

 rocks which lie between the Yirgu- 

 lian and the Oxfordian beds. By 

 the aid of a personal examination of 

 the spots, aided by the definite facts 

 recorded, when rightly interpreted, 

 one may come to a pretty sound con- 

 clusion. 



! This portion of the series may be 

 first examined in the valley of the 

 Eognon. Passing down this valley 

 from Andelot towards Donjeux, the 

 Corallian rocks, in the form of rubbly 

 limestones with Cidaris florigemma, 

 are first seen on the left bank of the 

 stream at Roche-sur-Rognon. Their 

 base is not here well exposed ; but 

 is stated (19) to consist, in the neigh- 

 bourhood, of disaggregated oolites 

 with Glypticus hieroglyphicus, over- 

 lain by white coral-limestone. On 

 the opposite side of the stream the 

 rubbly • limestones are themselves 

 absent, their place being taken at 

 Cultra by compact Oxfordian lime- 

 stones, similar to those which occupy 

 so much of the ground below them 

 (by general dip) on the left bank. 

 This is doubtless due to a fault; 

 though Tombeck (65) actually thinks 

 the rubbly limestones 100 feet thick 

 have changed into this compact well- 



