68 The A iiierirfoi Geo?(U//sf. January, 1895 
of till' jiiibbro inaiiilv in slnicturc. TIh-v foiisist of agj;rfjiali'S of rouiidcd 
(liiilliijrc, hypcrstliciic, iuul f)la;iiocl!isc, all of wiiifh minerals arc prosoiit 
also in the normal rofks. TIic basic rocks an' rej^'ardt'd as probably dif- 
fcrcnliati'd pliascs of tbc jrabbro, of farlier n'^e (ban tbc ^roat, mass of 
tlic normal rock, while the <,M'anidific phases ari' simply stnicl iirai peri- 
pheral phases. 
The roittact pheiiiDiiciKi at I'i</i'i>ii point, Mlitncsotn. \\ . S. ii.wi.KY. An 
exhibition of six'cimeiis. 
The relation of i/rniii to (Uxtiuicr from iinirfiin in ceHam rocks. Alfred 
C liANK. l)esci-ii)tion of the variation in texture and j^rain of some 
(jwarl/- diabasedikes of the northern peninsula of Michigan, and com- 
parison with etfusive Hows of similar mineral composition. Interstitial 
micropegmatite is primary or pnoumatolytic, and the feldspar crystal- 
lization l)e,ii'an before that of the augite, continuing until later. The 
main object of the paper was to elicit, by discussion, the best metliods 
of measuring the coarseness of grain of a rock. 
Crystallized xlaijs from copper-smelt in;/. Ai-kkkdC. Lane. Describing 
(with exhibition oi' specimens) some slag from the cupola furnaces used 
in copper-smelting, with large melilite crystals, Ix'tween one and two 
centimeters scjuare, interesting optically and in mo(b' of occurrence. 
Crystallized hematite is also noted. 
On the honetfeombed limestones in the bottom of lake Huron. Uor.KnT 
Wv'AA,. The limestones over a certain region in the bottom of this lakr 
are ascertained by the fishermen to be extensively eroded in a peculiar 
manner which the writer calls honeycombing and ])itting. This condi- 
tion is ascribed to a differential solul)ility of tlie rock in the presence of 
slightly acidulated water. 
On the nomenclature of the jine-firained .^Herons rocLs. Lkon S. (inis- 
WOIiD. 
On some dikes containing "huronite." Ai.khed E. Hakj.ow. A petro- 
graphical notice of certain dikes of diabase north and northeast of lake 
Huron, containing "huronite," as the mineral was named by Dr. Thom- 
s(tn in ]HM. It is found to be an imi)ure or altered form of anorthite, 
which has undergone either partial or complete "saussuritization," 
owing to metamorphic action. 
The rhararteristie features (f the ('(ilifor)ti(t <jold <i>i(irtz reins. ^VALl)K- 
MAK LiXDOHKN. 
On the (iiievrtz-keratophyre and its a.'<sociated rocks of the Baraboo bluffs, 
Wisconsin. Samuel Weidman (introduced by W. H. Hobbs). In the 
vicinity of Haralwo, Wis., acid pori)hyritic rocks occur of pre-Cambrian 
age. which correspond chemically with quartz-keratophyres. They ex- 
hibit under the microscope fluxion, spherulitic, poikililic, and other 
structures of \()lcanic rocks, and are associated with volcanic breccias 
which show them to have their origin in asurface flow. 
The (/)-anitis <f Pike's Pt((k. Colorado. EinvAiU) 11 Matthew (intro- 
duced by W. H. 'Clark). An areal and ])etrographical description of tlu' 
granitescomposing tiie soutliern end of the Rampart or Colorado rang", 
showing that great macroscopic variation may result while the micro- 
scopic characters remain monotonously uniform. 
A new intriisirc rock near Si/)-aeii.^e, Keir York. N. H. Dakton and 
J. F. Kemp. 
On the decomposition <f the r/ranite rocks of the Distrtet <f Colombia. 
(iEOKOE P. MEKHILL. 
Ancient plinsioffraphy as represented in sediments. Bailey Willis. 
Serpentine pseudomorphs after olivine, formerly called queirt-.-psetidomorphs, 
yfiddlefcld. Ma.'<s. B. K. Emeiison. 
Skeleton crystals of salt which hare been called chiastolite and later sj>i//el. 
from the Trias, Wesf.field, Mass. B. K. Emerson. 
Jiadiating pnrkerind of eorundam crystals around allanite. PeUiatn. M<iss. 
ii. K. Emerson. 
