22 



SCIENCE. 



[N. S. Vol. II. No. 27. 



Columbia, which possesses the herbarium 

 of Meisner, the last general monographer of 

 the genus, and to this has been added the 

 choicest of the other collections of the coun- 

 try. While Mr. Small has done no small 

 am.ount of field work on some of the forms, 

 the result appears to be worthj' of the facil- 

 ities he has enjoj'ed, though, like all mono- 

 graphic essays, its strength or weakness 

 must be tested by practical use. Keys to 

 the sub-genera and to the species under each 

 of these, and plates representing the habit 

 and the more essential details of each 

 species, render the work easy to use, and 

 the anatomy of representatives of the sev- 

 eral groups has been comparatively studied 

 and largely illustrated. In appearance the 

 monograph is good, and the plates are clearlj^ 

 drawn and well printed, though a little flat 

 and harsh — a defect that the artist will 

 doubtless overcome in future work. 



Wm. Teelease. 



The Geological and Natural History Survey of 

 Minnesota. The Twenty-third Annual He- 

 port, for the year 189 Jp. N. H. Winchell, 

 State Geologist. Minneapolis, Han-ison 

 & Smith, State Printers. 1895. 8vo. 

 255pp. 



This survey has kept steadily on its way 

 for many years, under the able direction of 

 Professor Winchell, who gives us annuallj' a 

 volume in which matters of practical im- 

 portance to the people of Minnesota and 

 questions of general scientific interest aUke 

 find efficient treatment. 



In the present volume, after a summary 

 statement of the year's work of the Survey, 

 Professor Winchell, in Part II., discusses 

 the Origin of the Archaean Greenstones of 

 Minnesota. This paper is of the nature of 

 a review of Bulletin No. 62 of the U. S. 

 Geological Survey on the Greenstone Schist 

 areas of the Menomee and Marquette Re- 

 gions of Michigan, by Dr. George H. Wil- 

 liams, in which the tendency of the conclu- 



sions reached by Dr Williams is to refer 

 the greenstones as a body to dynamic meta- 

 morphism of massive eruptive rocks, while 

 a sedimentary origin is not denied to a part 

 of them. Professor Winchell skilfully ar- 

 rays the facts, both megascopic and micro- 

 scopic, in support of his own view of the 

 origin of these greenstones, and would re- 

 verse the main conclusion of Dr. Williams 

 as to the comparative amounts of the two 

 sorts, massive and sedimentary. His con- 

 clusions are given in the foUomng words : 

 " We look upon the greenstones in Minne- 

 sota as an oceanic terrane having a definite 

 stratigraphic position (the uppermost part 

 of the Keewatin), although probably in- 

 volving some truly irruptive masses. Its 

 materials, both basic and acid, are inter- 

 bedded by sedimentation the one -ndth the 

 other, and are sometimes mingled. The 

 decayed condition of these materials is due 

 to the natural action of the Keewatin ocean 

 prior to consolidation, and the crystalline 

 condition of the lower beds is due to later 

 metamorphism which, having its active 

 forces and seat at greater depths, did not 

 permeate the whole formation. It is not 

 attributable so much to djTiamic move- 

 ments as to internal heat. Wherever such 

 movements operated with much violence, 

 the lower Keewatin sediments were fused, 

 producing irruptive felsytes and granite. 

 Such granite is bordered usuallj' by belts of 

 crj^stalline schist, evidentlj^ formed at the 

 time of such fusion." 



Part III. is devoted to a preliminary re- 

 port on the Eainy Lake Gold Eegion, by 

 H. V. Winchell and U. S. Grant, in which, 

 after an introductorj' part on the occurrence 

 and associations of gold ores, and a histori- 

 cal sketch of the gold discoveries of this 

 region, the body of the report is devoted to 

 the general features and geologj' of the area 

 and a more detailed account of individual 

 properties. Most of the gold-bearing rocks 

 of this district belong to the Keewatin di- 



