256 Dr. Irving — On the Airolo Schists. 



Dr. Grubenmann works out a section in the Val Canaria (a gorge- 

 like valley cut into the north slope of the Val Bedretto and across 

 the main strike of the beds) on the south flank of the great Gott- 

 hard massif. Of this the following may be taken as an outline 

 (the numbers denoting the ascending orders of the rocks on the 

 mountain-flank) : — 



The Val-Canakia Section (after Grubenmann). 

 7. The Uppermost Zone of 2-mica Schists : containing below whitish 

 and green mica-scales, dark green biotite, increasing in the upper 

 part until the proportions of white and dark mica become nearly equal. 

 From this point the section passes upwards into the "amphibole- and 

 garnet-bearing schists of the southern schist- and gneiss-zone of the 

 Gotthard massif." Tn addition to quartz and calcite, microscopic 

 examination shows them to be tolerably rich in small black mineral 

 particles (magnetite?), along with pyrites, haematite, and (sparingly) 

 rutile. Tourmaline and zircon occur as accessory minerals 

 (thickness ?) 



6. The Upper Zone of Gypsum, Ravchivaclce, and Dolomite : exposed 

 in a wild gorge difficult of access (previously described by von 

 Fritsch), but furnishing, in the insoluble residues after prolonged 

 treatment with acids, margarite, biotite, quartz (in grains), tour- 

 malines, rutiles, and zircons (thickness ?) 



5. The Second Zone of 2-mica Schists (containing disthene) : 

 comprising — 



(a.) Dark-grey, coarse, stratified calc-mica-schist = 4 metres. 

 (b.) Calcareous and ferruginous quartzite (thickness ?) 

 (c.) A 2-mica schist (very feebly stratified), of grey colour and 

 pearly lustre, apparently much slickensided (as of a ' shear-zone '), 

 containing, besides the two micas, rutiles, tourmalines, quartz, 

 calcite (sometimes as a pseudomorph after zoisite), an opaque 

 black mineral (with limonitic covering of the grains), earthy 

 clay material = 1 \ metres. 



4. The Kalkglimmerschiefer 1 (calc-mica-schist) : a clear-grey argil- 

 laceous schistose limestone, with quartz grains, with light and green 

 mica-scales on the foliation-planes and a talcose mineral adhering to 

 the quartz-grains, interlaminatecl with feeble layers of a micaceous 

 quartzite (half-schistose, half-granular), and of strongly ferruginous 

 quartzite, terminating upwards in a bed of marble (1^ metres) 

 = 300 metres. 



3. Garnet-bearing Schists (Thonglimmerschiefer) : interstratified 

 with quartzite, and falling into three principal groups : — 

 (a.) An upper group of dark grey schists (4 metres). 

 (b.) A grey brown granular quartzite with included mica, 

 'opaque Erzmassen,' pyrite, and amorphous limonite (10 metres), 

 (c.) A. lower group of brown highly lustrous schists (1 metre). 

 The schists contain garnets (often greatly deformed by pressure), 

 two micas (probably margarite and biotite), quartz particles, 

 tourmalines, rutiles, and zoisite. 



1 ' Calcitglimmerschiefer ' of Kalkowsky, El. der Lith. p. 199. 



