OF CAKBONIFEROTJS AGE AT GTJTTANNEX. 391 



clever imitation of that rock. Thus, if Nature has done the same in 

 a few limited instances, or if. by subsequent crushing of the 

 materials or secondary development of minute minerals, she has 

 made it diiScult now and again to distinguish between any such 

 mosaic and a truly crystalline rock, we are not thereby justified in 

 calling the former a gneiss or a schist, unless we are prepared to 

 use a scientific terminology in a merely popular sense. We must 

 also remember that identities cannot be legitimately inferred from 

 the comparison of damaged specimens from the two classes of rocks. ^ 



On the map of the Swiss Geological Survey (Blatt xiii.) a belt of 

 sericitic phyllites and gneisses — presumably of Carboniferous age — is 

 represented as crossing the Haslithal at and above Guttannen. 

 Here it is rather more than a mile wide, and extends diagonally 

 across the map in a direction roughly from E.K.E. to W.S.W.^ 

 Below that village the valley of the Aar is excavated in gneiss. 

 This rock at last (near Imhof) disappears under the thick zone of 

 Mesozoic strata which enclose the Lake of Brienz, A short distance 

 above Imhof the road mounts gradually towards Guttannen, and 

 the traveller can examine, here and there, the aforesaid gneiss. This 

 has a general resemblance to the rock over which I passed in ISSS 

 as I walked up the Gadmenthal. It commonly varies from a 

 rather fine-grained to a moderately coarse gneissoid rock, sometimes 

 banded, but usually not conspicuously so. It exhibits indications 

 of crushing, but is not, as a rule, very fissile. 



As Guttannen is approached, erratics of a rather dark schistose or 

 gneissose rock — the Carboniferous rock in question — become fairly 

 abundant, and at last, about a furlong or two from the village, are 

 very numerous on the western side of the road. They are darker 

 in colour and rather more micaceous than the ordinary gneiss of 

 the district, from Avhich as a rule they are readily distinguished. 

 The blocks have obviously descended, at any rate in great part, 

 from a combe beneath the crest of the mountain-ridge on the 

 western flank of the vaUey. 



Lying by the road on the opposite side, as the village is entered, 

 are two very large erratics, ' which, however, have been reduced in 



^ I mean this : Crushing gives to a crystalline rock a clastic structure and 

 is favourable to the development of secondary minerals. On a rock already 

 clastic it has the latter effect, and sometimes injures the characteristic outline 

 &c. of the fragments. Thus the two rocks, so different in origin, may be re- 

 duced uearl}^ to the same condition. But to a similarity thus produced we 

 must not appeal : we might as reasonably argue that two coins were of the same 

 reign when both were rubbed smooth, or that the language on two pieces of 

 manuscript had been identical when the characters on each were blurred 

 bejond recognition. 



- That is to say, it extends for several miles. On the northern side is 

 ' Gneiss,' on the southern ' Bank-granif, Gnciss-granit, Aiigen-gneiss' Into 

 minor details it is needless to enter. We are agreed, I believe, that these are 

 very ancient rocks. 



^ About 60 yards from the door of the ' Ear ' Inn. We got this information 

 from an elderly man, who lived in the next house to the Inn, and was, I think, 

 a relation of the landlord. After hearing the details into which he entered we 

 felt no hesitation in accepting his statement. From this block I took specimens 

 which will be presently described. 



