642 REVIEWS 
metamorphic origin and the additional evidence of the degenerative 
granulation of the crystalline rocks as a result of great pressure. 
The report of Mr. Low on his remarkable explorations in the 
Labrador peninsula contain a vast amount of new and important infor- 
mation respecting this heretofore ¢erra incognita. It isimpossible to sat- 
isfactorily summarize this. It shows that besides vast areas of gneisses 
and granitoid rocks presumably referable to the Laurentian series, 
there are extensive belts of later rocks of clastic origin referable to the 
Huronian and Cambrian series as interpreted by the Canadian survey. 
The rocks classified as Cambrian comprise beds of arkose rock, sand- 
stone, chert, dolomite, felsitic shale, argillite and argillaceous shale» 
together with gabbro, diabase and fine-grained decomposed traps and 
volcanic conglomerates. ‘They appear to embrace those debatable beds 
which are referred by some of the United States geologists to pre-Cam- 
brian horizons. There is ground to hope that this extended area of 
these formations will afford the means for their complete elucidation. 
The observations of Mr. Low have made it clear that this great Labra- 
dorean area has a complex geological structure and is far from being 
properly characterized as simply Laurentian or even Archean. 
Mr. Low’s contributions to glacial geology are very important. 
They show an outward movement in all directions from the center of 
the peninsula. He locates the central névé ground (which is charac- 
terized by only slight traces of glacial motion) midway between the 
east and west coasts of the peninsula, and between 53° and 55° latitude. 
Its southern boundary is in places from 150 to 200 miles north of the 
southern water-shed. ‘The report is accompanied by ‘“ Notes on the 
Microscopical Structure of some of the Rocks of the Labrador Penin- 
Sulla.” loyy IMile, Wi. Ihe leeriniere, 
The chemical, mineralogical and statistical reports embrace a large 
mass of valuable data. Altogether the report is one of the most 
important issued by the survey. THEE 
Iowa Geological Survey, Vol. VI. Report on Lead, Zinc, Artesian 
Wells, etc. SAMUEL CALVIN, State Geologist, A. G. LEON- 
ARD and El.) FE. Bat) Assistant) State Geologistss) (Des 
Moines, 1897. 
This volume of 487 pages embraces reports on the ‘‘ Lead and Zinc 
Deposits of lowa,” by A. G. Leonard; “‘The Sioux Quartzites and Cer- 
