Geology and Mineralogy. 89 



The third part embraces such discussions and comparisons as 

 to genesis and relationship as appear to be the result of the fore- 

 going, and may be regarded as the petrographic geology of the 

 State. l. v. p. 



2. JStude miner alogique et petrographique des Roches gabbro'i 

 ques de VJ^Jtat de Minnesota, J&tats Unis, et plus specialment des 

 Anortho sites ; by A.N. Winchell. Inaug. Diss., Paris, 1900, 8°, 

 pp. 164, pi. 8. — This work, which is being published in English 

 in a journal devoted to geology, is a very careful, minute and 

 painstaking petrographic examination of a series of the gabbroid 

 rocks of Minnesota. It is accompanied by a series of analyses 

 and a number of general conclusions upon the inter-relations of 

 the gabbroid magmas are brought out. Especially noticeable is 

 the detail and care with which the micro-mineralogy of the com- 

 ponent minerals has been worked out. l. v. p. 



3. Les Roches iSruptives des Environs de Menerville, Algerie ; 

 by L. Duparc, F. Pearce and E. Ritter. Mernoires de la Soc. 

 de Phys. et d'Hist. Nat. de Geneve, xxxiii, No. 2, 4°, pp. 142, 

 pi. 8. — The region whose eruptive rocks have furnished the sub- 

 ject of this memoir lies about 40 miles east of the city of Algiers. 

 There is an important massif of granite, and in the general 

 neighborhood of this extensive areas of rhyolites (liparites), dacites 

 and andesites. All these are carefully described from the petro- 

 graphic point of view by the first two authors, with many ap- 

 pended analyses. The collection of the material and the geologic 

 portion of the work is by the last-named author. l. v. p. 



4. The Charnockite Seines, a group of Archean Hyper •sthenic 

 rocks in Peninsular India ; by T. II. Holland. Memoirs Geo] 

 Surv. India, vol. xxviii, pt. 2, pp. 130, pi. 8. — The author states 

 that the name charnockite is intended for local use and conve- 

 nience alone. Although these rocks are of great age, and have 

 thus lost some of the distinctive features of igneous intrusions, 

 they are nevertheless to be clearly regarded as such, and the 

 author takes great pains to give the evidences on this point with 

 fullness and detail. The nearest equivalents of these rocks among 

 types previously described are found in the group of " pyroxene 

 gneisses." The study of the field relations is supplemented by 

 petrographical and chemical investigations. l. v. p. 



5. Geologische Skizze der Besitzung Jushno-Saoserk und des 

 Berges Deneshkin Kamen innordllchen Ural ; by F. Loewinson- 

 Lessing. 8°, pp. 25 7, pi. 9, Dorpat, 1900.— This volume is pub- 

 lished in Russian, but a resume of 87 pages in German will serve 

 to greatly extend its readers among geologists. After a brief 

 description of the region, the Devonian sediments and the gold- 

 placer mines, the main body of the work is taken up with the 

 petrography of the igneous rocks. Several varieties of these are 

 described in detail, the chief interest centering in those rich in 

 lime, iron and magnesia, a group of gabbros, norites, pyroxenites, 

 dunites, etc. Analyses of these rocks are given and there is a 

 general discussion of their magmatic relations. l. v. p. 



