January 27, 1899.] 



SCIENCE. 



141 



aggregates of pink microcline, natron-ortho- 

 clase, quartz, biotite and ilmenite to prac- 

 tically pure quartz, intermediate varieties 

 being present. The paper concluded with 

 a general review of the granites of the At- 

 lantic sea-board and stated that they are 

 with few exceptions biotite granites. Such 

 analyses as are available were used in il- 

 lustration. 



In discussion of the last three papers M. 

 E. Wadsworth remarked with regard to 

 the amphibolites of the second paper the 

 similar changes in peridotite dikes on Lake 

 Superior and their clear igneous character. 

 In reply J. F. Kemp mentioned the serpen- 

 tines near New York, which have lately 

 been shown by D. H. Newland to contain 

 recognizable olivine, and which are prob- 

 ably altered basic, igneous rocks. Whit- 

 man Cross stated that the Colorado granites 

 with which he was familiar had sharp con- 

 tacts with the wall rocks and showed no 

 such infusion as described by Professor 

 Emerson. They resembled rather the gran- 

 ites of the Long Island Sound region. M. 

 E. Wadsworth remarked that he had al- 

 ways been able to find evidence of the in- 

 trusive nature of massive granites wherever 

 he had searched for it and he controverted 

 the idea that metamorphism was respon- 

 sible for them. Referring to the supposed 

 post-Carboniferous age of the Conanicut 

 granite J. E. Wolff stated that he and his 

 associates at Cambridge had reached the 

 conclusion that the granite intruded Cam- 

 brian and not Carboniferous strata. In re- 

 ply to the remarks of AVhitman Cross, B. 

 K. Emerson again reviewed his interpreta- 

 tion of the Massachusetts phenomena. 



Augite-syenite near Loon Lake, N. Y. H. P. 



CusHiNG, Cleveland, O. 



An interesting section exposed in a rail- 

 road cut near Loon Lake shows an intru- 

 sive rock which has caught up fragments 

 of the Grenville series. The rock is related 



to the augite-sj'enites but the chemical, 

 analj'sis shows some unusual features. A 

 large area of anorthosite mapped in Frank- 

 lin county, N. Y. , the past summer, was 

 found to grade into similar rocks on all 

 sides, and they are, therefore, regarded as 

 variants of the gabbro magma. They present 

 a range from rocks of the acidity of granite 

 to basic gabbros. The analysis quoted was 

 by E. W. Morley and was as follows : 



SiO, 63.45, TiO, 0.07, Al.O, 18.31, Fe^O, 

 0.42, FeO 3.56, MnO none, CaO 2.93, BaO 

 0.13, MgO 0.35, K,0 5.15, Hafi 5.06. Loss, 

 0.30. Total, 99.73. The rock is composed 

 of microperthite, quartz, hyperstheme, a 

 pyroxene near diallage and a little plagio- 

 clase. It was compared with Cape Ann 

 and Norwegian relatives. 



In discussion J. F. Kemp remarked the 

 presence of related rocks in the Adirondack 

 region south of Professor Cushing's area 

 and the possibility of others having been 

 pinched into the gneisses and disguised by 

 metamorphism. H. S. Washington empha- 

 sized their close parallelism with the Cape 

 Ann varieties described by him. M. E. 

 Wadsworth discussed the passage of Min- 

 nesota gabbros into rocks of this type, and 

 N. H. Winchell gave a most interesting re- 

 view of recent results in the study of the 

 Minnesota gabbros and their relatives. Be- 

 ginning with anorthosites be showed their 

 passage into gabbros and their occurrence 

 both as inclusions and as segregations in 

 diabases. The gabbros grade into the 

 ' muscovadites ' of the Minnesota geologists 

 and the muscovadites into greenstones and 

 perhaps into jaspilite and iron ore. R. A. 

 Daly remarked the presence of the same 

 rocks as those described by Cushing in Mt. 

 Ascutney, Vt., and quoted an analysis that 

 was very much like Cushing's. He outlined 

 the curious change in color that the rock 

 undergoes when quarried. He stated that 

 it also occurs at Cuttingsville in the Kil- 

 lingly Peaks, Vt. 



