Notices respecting New Books. 463 



gneisses, granitells, augite-schists, hornblende-schists, chlorite- 

 schists, mica-schists, porphyries, olivine-diabases, peridotite, dio- 

 rites, uralitic gabbros, altered porphyritic diabase, norites, vein- 

 quartz, magnetic siliceous schist, argillaceous quartz- schists, and 

 quartzites, are the chief kinds of rock here treated of. Mr. Irving's 

 "summary of results" (pp. 712-714), as to the local extent and 

 the relationships of these great schistose masses, of Huronian 

 and probably Laurentian ages, with their associated eruptive rocks, 

 is concise and useful. He says in conclusion : — "Mr. Yanhise's study 

 shows now that augite, so far from being a stranger to such rocks 

 as gneiss and granite, is nearly as common a constituent, so far 

 at least as this region is concerned, as hornblende or mica, and 

 that all the hornblende of the rocks of this region is but altered 

 augite. My o vn examinations of many hundred sections of the 

 eruptwe rocks of the Copper-bearing Series of Lake Superior have 

 convirced me that in those rocks also there is no hornblende that 

 is not secondary ; and, while I am not at all prepared to say 

 that there is no such thing as original hornblende in the older 

 crystarine rocks, I am sure that there is far less of it than has 

 heretofore been supposed. Many diorites are, thus, but uralitic 

 or altered diabases and gabbros ; while many syenites, hornblende- 

 granites, hornblende-gneisses, and hornblende-schists are also but 

 altered augitic rocks. The existence of this wide-spread alteration, 

 ard of another equally important one, which I have elsewhere 

 shown to obtain widely in the rocks of the Lake-Supex'ior region, 

 name 1 y, the sabstiiution of secondary quartz for primary felspars, 

 makes it very evident to me that any one attempting to solve the 

 problem of the origin of the crystalline schists must give much 

 attention to the matter of internal alterations and replacements:' 



Part VIII. (pp. 715-723), based on the observations of Mr. A. C. 

 Clarke, and edited by the Chief Geologist, Prof. T. C. Chamberlin, 

 is a succinct notice of the "Superficial Geology of the Upper 

 Wisconsin Valley;" treating of its glaciation, the valley-flood- 

 deposits, earlier glacial deposits, morainic accumulations, boulder- 

 clay or till of the Second Glacial Epoch, peculiarities of drainage, 

 soils, and native vegetation. 



Part IX. (pp. 725-754) is a concise account of the " Geological 

 Survey," being a " sketch of the geodetic work done in the State 

 since 1874, under the auspices of the United-States Coast and 

 Geodetic Survey, together with a short outline of the principles 

 and methods pursued in the triangulation, accompanied by two 

 maps, one showing the triangulation executed and proposed, and 

 the other the difference between the positions of the trigonometrical 

 stations as given by ordinary surveys and the same in their true 

 position on the Spheroid." By John E. Davies, Professor of 

 Phvsics in the University of Wisconsin, and Chief of the Geodetic- 

 Survey in Wisconsin. With an Appendix by C. A. Schott, Chief 

 of the Computing Division of the U. S. Geod. Survey, on " the 

 measurement and resulting length of the secondary base-line near 

 Spring-green, Sauk County, Wisconsin, in 1878." 



