Xevill PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
Nord. and the Loire Inférieure, and in other places in Brittany into 
syenite. He also mentions that they sometimes present the appear- 
ance of quartziferous porphyry and petrosilex, and not only pass 
into diallage rock, but like serpentine contain oxidulated iron, as in 
Scandinavia. After citing various other examples, such as the pass- 
age in Norway of granite into the syenite, in which so many rare 
minerals are discovered, M. Durocher remarks that the variations 
are not so extraordinary as they appear, these igneous rocks contain- 
ing the same elements,—silica, alumina, potash, soda, lime, magnesia 
and oxide of i iron; granite being the most rich im silica and alumina, 
the poorest in eo magnesia, oa oxide of iron. When a granite 
becomes hornblendic and passes into syenite, the proportion of lime 
and oxide of iron augments, while that of alumina and potash or soda 
diminishes. In the change of the hornblendic into augitic, diallagic 
and hypersthene rocks there is but little difference in the elements ; 
the hornblendic rocks are richest im silica and alumina, the augitie 
in lime and oxide of iron, and the diallage and hypersthene rocks in 
lime, and more especially magnesia. The hornblendic rocks being 
those which contain most silica, often too much to be altogether com- 
bined, form as it were the transition from those in which free silica 
is found, such as granite, to the augitic, diallage and hypersthene 
rocks, where silica is altogether combined with bases. 
M. Frapolii read a paper on M. Desor’s notice of the erratic block 
phenomena of the north, as compared with those of the Alps, m 
which he calls attention to the immense quantity of fragments of ice 
armed with blocks and pebbles, which are driven about the coasts of 
the north by the storms of winter and spring, grinding against the 
cliffs and the rocks. The coasts of Scandinavia, he remarks, are well 
known to be encased by a thick coating of ice, which when broken 
up carries the blocks and pebbles with it. The masses of block- and 
shingle-bearing ice put into motion by the tides and winds range along 
the shore, polishing and scratching the rocks according to their sur- 
faces and position ; the cliffs being scratched in horizontal lines along 
the fiords, and in other similar situations. M. Frapolli cites a map 
of M. Weibye, of Kragero, upon which the latter has laid down with 
great precision the scratches and furrows on the rocks of the country 
bordering the sea in the Bradsbergsamt, and quotes the inference of 
M. Weibye, ‘‘that the scratches and furrows on horizontal or nearly 
horizontal surfaces take a direction always perpendicular to the gene- 
ral line of coast in open bays, and always parallel to the range of the 
channels in narrow fiords; that the horizontality, or the greater or 
less inclination of the scratches on the inclined or vertical surfaces 
depends on the relief of the coasts of the locality, and always corre- 
sponds with this relief, and with the action of the different winds.” 
From personal observations M. Frapolli considers that the scratches 
and furrows observable in Scandinavia may be referable to the action 
of ice floated about, always taking into consideration the configura- 
tion of the coast when the levels of sea and land changed. And cer- 
tainly the freezing of the sea on coasts, the consequent encasing of 
blocks and shingles in ice, the drifting of this ice, together with the 
