Reports and Proceedings — Geological Society of London. 571 



On Glacial subjects the antlior has enlarged his views, and he is 

 prepared to admit " that land-ice can in some way give rise to the 

 formation of a Boulder-clay." In cases, however, where there is 

 a diiference of opinion amongst geologists, care is taken to state 

 the alternative views. 



The work is illustrated by 214 figures and two plates ; and 

 altogether it forms an excellent and comprehensive handbook for 

 advanced students. 



E-iBiPoiaTS ji^isTiD :PK,ooE:EiDiisrc3-s. 



Geological Society op London. 



November 9th, 1892.— W. H. Hudleston, Esq., M.A., F.R.S., 

 President, in the Chair. 



The President announced that the Naturforschende Gesellschaft 

 of Dantzig will celebrate their 150th Anniversary in that town on 

 January 2nd and 3rd, 1893. 



The following communications were read : — 



1. "A Sketch of the Geology of the Iron, Gold, and Copper 

 Districts of Michigan." By Prof M. E. Wadsworth, Ph.D., A.M., 

 F.GS. 



After an enumeration of the divisions of the Azoic and Paleozoic 

 systems of the Upper and Lower Peninsulas of Michigan, the Author 

 describes the mechanically and chemically formed Azoic rocks, and 

 those produced by igneous agency, adding a table which shows his 

 scheme of classification of rocks, and explaining it. 



The divisions of the Azoic system are then described in order, 

 beginning with the oldest— the Cascade Formation, which consists 

 of gneissose granites or gneisses, basic eruptives and schists, 

 jaspilites and associated iron ores, and granites. 



The rocks of the succeeding Republic formation are given as 

 nearly as possible in the order of their ages, commencing with the 

 oldest : — Conglomerate, breccia and conglomeratic schist, quartzite, 

 dolomite, jaspilite and associated iron ores, argillite and schist, 

 granite and felsite, diabase, diorite and porodite, and porph^a-ite. 

 The author gives a full account of the character, composition, and 

 mode of occurrence of jaspilite, and discusses the origin of this 

 rock and its associated ores, which he at one time considered eruptive; 

 but new evidence discovered by the State Survey and the United 

 States Survey leads him to believe that he will have to abandon that 

 view entirely. 



In the newest Azoic formation, the Holyoke formation, the 

 following rocks are met with : — Conglomerate, breccia and con- 

 glomeratic schist, quartzite, dolomite, argillite, greywacke and 

 schist, granite and felsite (?), diabase, diorite, porodite, peridotite, 

 serpentine, and melaphyre or piciite. The conglomerates of the 

 Holyoke formation contain numerous pebbles of the jaspilites of the 

 underlying Republic formation ; a description of the Holyoke rocks 

 is given, and special points in connexion with them are discussed. 



