326 SCIENTIFIC RECORD FOR 1882. 



gneisses in the Austrian Alps, besides an intermediate group, which he 

 comijares with the Hurouian. Hunt, from his recent observations, 

 announces that the upper gneissic series, as examined by him on the 

 southern slope of the St. Gothard, and in the Ticino, are clearly of the 

 type of the Montalban of North America, seen in the White Mount- 

 ains of New Hampshire, and near Philadelphia. The tunnel of the 

 St. Gothard passes through about 2,000 meters of the older gneiss, on 

 the north, and 13,000 meters of the younger series, the strata of this 

 along the line being generally at a very high angle, and much con- 

 torted and faulted, but often lying at low angles in the Ticino. The 

 typical pietre verdi, or Huronian 'series, is here wanting, though seen over 

 large areas in northern Italy, with its serpentines, argillites, chloritic, 

 steatitic, epidotic, hornblendic, and feldspathic rocks, including so- 

 called gabbros and euphotides. Hunt has given in this connection an 

 account of his recent observations near the foot of Mont Viso, in the 

 vicinity of Biella, in the province of No vara. Here he found the older 

 gneiss highly contorted, having the characters of the Laurentian, and 

 including bands of granular limestone, with graphite, pyroxene, quartz, 

 and other characteristic minerals. This is overlaid to the westward by 

 an area of the pietre verdi orHuronian series, which is immediately suc- 

 ceeded on the west by Montalban gneisses and mica-schists. The south- 

 ward course of the eastern border of this series is such as to rapidly 

 reduce in this direction the considerable breadth of the Huronian, and 

 if continued for a mile or two beneath the superficial deposits in the 

 valley of the Cervo would bring the newer gneisses in juxtaposition 

 "with the Laurentian, as in the St. Gothard section. 



The gneisses and mica-schists of the Saxon Erzgebirge have, accord- 

 ing to the same observer, the lithological characters of the Montalban 

 or younger gneiss series (and the same is true of the Granulitgebirge of 

 Saxony), with their included beds of gabbro and serpentine. It may be 

 here remarked that the characteristic Montalban gneisses in America 

 pass into granulite or leptinite on the one hand, and into gneiss and 

 quartzose mica-schist on the other. 



Saner has found in several localities in the gneiss and mica-schist se- 

 ries of the Erzgebirge, conglomerates holding, in a crystalline gneissic 

 matrix, pebbles occasionally of quartzite or granular limestone, but more 

 often of gneiss. These rolled masses, often several inches in diameter, 

 represent different varieties of gneiss common to the older series of the 

 Alps, and in the opinion of Hunt, who has examined them, are doubts 

 less pebbles derived from Laurentiau strata. He has noticed a similar 

 occurrence of granular limestone jjebbles in a hornblendic gneiss in the 

 White Mountains. Pebbles of gneiss are also found in like conditions 

 in gneisses in Sweden and in southeastern France. 



The age of these Saxon gneisses is, according to Credner, clearly pre- 

 Cambrian. The late researches of the geological survey of Saxony have 

 shown that this is also true of the gneissic area formerly supposed by 



