348 General Notes. 
ably the result of the action of dynamic agencies upon eruptive 
rock e serpentines are shown to be derived from a peridotite, 
composed sometimes of bronzite, hornblende and olivine, and at other 
times essentially of olivine and tremolite. Different specimens of 
amphibolites contain zoisite, epidote, augite and tale. The most 
interesting rocks discussed in the paper are the eclogites. A variety 
which the author calls kelyphite-eclogite is made up of garnets and 
hornblende in a groundmass consisting of amphibole and ompha- 
cite, so intergrown as to imitate the granophyre structure of certain 
acid rocks. The garnets are frequently surrounded by a rim of 
hornblende and _ plagioclose, which, however, the author is disin- 
clined to regard as a reaction rim, but is rather disposed to look 
upon as a growth around the garnet as a center. Zoisite, which is 
also found in these eclogites, is often seen in the thin section to be 
surrounded by a rim of cloudy substance, which under high powers 
is resolved into plagioclose, muscovite and a third mineral with the 
specific gravity and optical properties of topaz, but in which no 
fluorine could be discovered. Patton supposes it to be an unknown 
mineral with the composition Al, Si O,.—The saussurite gab- 
bros of the Fichtelgebirge, found in lenticular masses scattered 
through serpentine layers, which are interstratified with clay 
slates and phyllites, are regarded by Michael! as the result of 
the alteration of a sedimentary feldspathic gabbro, although it 
would seem, from his own descriptions, that he would have been 
equally well justified in concluding that the saussurite gabbro lenses 
are merely the less altered remains of an intercalated gabbro, whose 
serpentine, or some indeterminable mineral, in other cases the new 
minerals produced are serpentine and a calcium garnet. 
Mr. Lawson,’ of the Geological Survey of Canada, gives an account 
of the diabase dykes so prevalent in the Archean region 
around Rainy Lake. These dykes have a width of from sixty to 
one hundred and fifty feet. Toward their centers they are eom- 
posed of plagioclose, augite and quartz, with a greater or less pro- 
portion of colorless garnets. The augite appears as an aggregate of 
little crystals which fill the spaces between the other constituents, 
and not as one continuous crystal, as is the usual case among 
es. The quartz and garnets are found only toward the centers of 
the dykes, and are absent at their edges. Idiomorphic enstatite, 0? 
the contrary, is a frequent constituent of material taken from the 
sides of the dykes, and is absent from their centers. The features 
: 2 Proceedings Gan. Enoittate Oe Meet, and American Geologist, April, 
