294 PROF. T. G. BONNEY ON" MESOZOIC ROCKS AND [Aug. 1 894, 



belt from the bed of tbe glen to the high road, which we reached 

 no long distance on the eastern side of the ' col.' The stream, from 

 which we started, was running over the Jurassic rocks. Ascending 

 by the more eastern of two ravines (after examining the lower part 

 of the other), we passed in succession over the following rocks : — 

 (1) the usual dark slaty rock, with an occasional more arenaceous 

 band, extending for a considerable distance up the slope ; (2) a slabby 

 whitish marble, which has a general resemblance to that at Alt- 

 kirche ; (3) a darkish subcrystalline and very slaty rock ; (4) a rock 

 more like 2, but less crystalline in aspect, more fissile, and greyer 

 in colour ; (5) a slaty, rather friable, lead-coloured limestone ; (6) a 

 darker and more slaty rock ; (7) a more sandy variety of the same ; 

 (8) the usual rather crushed and micaceous gneiss. The outcrops 

 2, 3, and 4 seem to have a steeper dip than the rocks above 

 and below, which obviously are Mesozoic, and their united thick- 

 ness is considerably less than that of either group. On reaching 

 the high road and going westwards we crossed back over 4, 3, 

 and 2 in succession, the last running at the back of a small 

 1 dependauce' of the Furka Hotel almost on the summit of the pass, 

 and being quarried close to the former building. 



The middle part of this section offers difficulties : 2 is the Alt- 

 kirche rock, 3 hardly presents in the field, or in hand-specimens the 

 aspect of true crystalline limestone, but rather that of a slaty sub- 

 crystalline Jurassic rock. When examined under the microscope it 

 is found to consist of grains of calcite, quartz, and pyrites, inter- 

 spersed with black carbonaceous matter. Certain grains of the 

 first exhibit a peculiar structure, developed by brown or black 

 staining, which resembles that characteristic of echinoderms ; these 

 very probably are fragments of crinoids. 1 Those in the matrix 

 generally are rather oval in form, about *05 inch long, and may be 

 compared (with it) to the matrix of the knotenschiefer'm the Nufenen 

 and Scopi districts. But some larger grains of calcite, which occur 

 now singly, now in -small clusters, including occasionally a grain of 

 quartz, suggest by their outlines the possibility that they are in reality 

 detritus from the marble. A second specimen, collected from the 

 above-mentioned locality by the high road, showed a similar struc- 

 ture, contained fragments of organisms, suggested the possibility of 

 detritus from the marble, and included quartz and a little felspar 

 apparently of detrital origin, the latter having been somewhat en- 

 larged subsequently. This rock not improbably corresponds with 

 No. 3' of the Realp section. But No. 4 of the Furka section seems 

 to be a true marble, so that, if our identification be correct, we have 

 here, as in the neighbourhood of Altkirche, not only the marble 

 thrust through the Jurassic rocks, but also a small portion of the 

 latter nipped between wedges of the former. 



1 As I was distrustful of my own experience, I submitted these slides to 

 Dr. G. J. Hinde, who most kindly examined them, and informed me that he 

 had no doubt of the organic (probably crinoidal) origin of some of the grains, 

 and that possibly other organic fragments were present, but that concerning these 

 it was difficult to be sure. 



