ANNIVERSARY ADDRESS OF THE PRESIDENT. lix 



of 75°, the planes of the cleavage being perpendicular to those of bed- 

 ding, and therefore dipping at an angle of 1 9° towards Mont Blanc, 

 under which, if mistaken for bedding, they would appear to pass. 

 Major Charters adopts Mr. Sharpe's opinion, that these strata dip 

 from Mont Blanc, and is therefore an advocate for his theory ; but 

 Professor Forbes has, on the contrary, disputed, in an able paper, 

 all Mr. Sharpe's statements, and vindicated the accuracy of the Swiss 

 observers, more especially of M. Favre, whose laborious excursions, 

 unchecked by danger and fatigue, and continued over many years, 

 fully merited the confidence demanded for him. In this paper Pro- 

 fessor Forbes points out, as a striking example, the secondary beds 

 of limestone on the road to the Chapeau, which, from some unex- 

 plained reason, Mr. Sharpe had not examined ; and, as I was myself 

 at Chamounix, I hoped to have verified this position of Professor 

 Forbes by personal investigation, and did so to a certain extent, though 

 a severe fit of illness somewhat restricted my observations. The beds 

 of limestone at the Chapeau certainly do dip towards the gneiss, 

 the beds or folia of which rise above at a higher angle than those of 

 the limestone ; but as the junction is concealed by detritus, no 

 positive conclusion could, in my opinion, be drawn from this circum- 

 stance. Reflecting, however, that M. Favre' s great discovery of 

 anthraxiferous beds resting horizontally on the peaks of the Aiguilles 

 Rouges proved that at least the secondary rocks had there been 

 deposited upon crystalline rocks, and subsequently lifted up with 

 them, thus affording an argument against the actual underlying of 

 such rocks by probably even more recent strata, I wrote to M. Favre 

 on the subject, and I shall now give an abstract of his very interesting 

 reply. In the summer he had visited, partly with M. De Verneuil, 

 the Valley of Chamounix, and had also studied the works of Sharpe 

 and Forbes : and after careful investigation he states that the rocks, 

 wherever visible, confirm the conclusions to which he had come in 

 1846 and 1847, namely, that the beds of limestone are nearly vertical 

 at the base of the Aiguilles Rouges, and dip at a high angle under 

 the chain of Mont Blanc, the crystalline schists reposing upon them, 

 and therefore dipping also under the chain. (See fig. 1.) In respect 

 indeed to this limestone, M. Favre states that the Belemnites which are 

 found in the more schistose beds are arranged parallel to the planes of 

 division, which therefore cannot be taken for planes of cleavage, but 

 must be true planes of bedding. At one point the distance from the 

 calcareous rock to the crystalline schists was only 3*2 feet, and a 

 plumb-line suspended from a point in the gneiss above would fall 

 far within the calcareous area. M. Favre considers the representa- 

 tion by Studer of the bent-up limestone between the Aiguilles Rouges 

 and Mont Blanc Ranges incorrect, and gives a section in which the 

 beds are horizontal on the top of the Aiguilles Rouges, then rest 

 at a high angle on their flanks, and dip under Mont Blanc ; — a section 

 also opposed to the views of M. Fretz, who, by introducing the anthra- 

 cites between the Jurassic strata and the schists, makes the phae- 

 nomenon one of inversion. 



So far it would appear that little more could be desired to resolve 



