weeks.] PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1804. 23 
15« Bascom (Florence). The structure, origin, and nomenclature of 
the acid volcanic rocks of South Mountain, Pennsylvania. 
Abstracts: Am. Geol., vol. xiii, pp. 122-123; Am. Nat., vol. xxviii, 
pp. 515-516. 
Noticed in Bibliography and Index for 1892 and 1893. 
10 Bashore (Harvey B.). The Harrisburg terraces [Pennsylvania]. 
Am. Jour. Sci., 3d ser., vol. xlvii, pp. 98-99. 
Describes the gravel deposits in this vicinity. 
17 Bayley (W. S.). The basic massive rocks of the Lake Superior 
region. IV. The peripheral phases of the great gabbro mass 
of northeastern Minnesota. 
Jour, of Geol., vol. ii, pp. 814-825. 
Describes the petrographic characters of the nonfeldspathic gab- 
bros and the olivine-pyroxene and pyroxene aggregates, and discusses 
the relation of the basic rocks to the normal gabbro. 
17a A summary of progress in mineralogy and petrography in 
1893. 
Colby University, Geol. Dept. 
Abstract: Am. Geol., vol. xiv, p. 52 (8 1.). 
18 Beachler (Charles S.). An abandoned Pleistocene river channel in 
eastern Indiana. 
Jour, of Geol., vol. ii, pp. 62-65, with map. 
Describes the evidences which indicate the former existence of a 
river chanel in Rush and Decatur counties in southeastern Indiana. 
19 Becker (George F.). On certain astronomical conditions favorable 
to glaciation. 
Am. Jour. Sci., 3d ser., vol. xlviii, pp. 95-113, figs. 1-3. 
Abstract: Am. Geol., vol. xiv, pp. 191-192. 
Discusses the variation of temperature as influenced by solar radia- 
tion and the effects of low eccentricity and high obliquity, and includes 
a calculation of sunshine per unit area. Concludes that the accumu- 
lation of glacial ice may be due to a combination of low eccentricity 
and high obliquity with a favorable disposition of land and water. 
20 [The genesis of ore deposits.] 
Am. Inst. Mg. Engrs., Trans., vol. xxiii, pp. 602-604. 
Discusses a paper by F. Posepny on the same subject, noticed in Bib- 
liography and Index for 1892 and 1893. 
21 Beecher (C. E.). On the mode of occurrence and the structure and 
development of Triarthrus becki. 
Am. Geol., vol. xiii, pp. 38-43, pi. iii. 
Describes the peculiar mode of occurrence of the trilobites found in 
the Utica shale near Rome, N. Y., and describes and figures the struc- 
ture of the legs and antennae of Triarthrus becki. 
22 The appendages of the pygidium of Triarthrus. 
Am. Jour. Sci., 3d ser., vol. xlvii, pp. 298-300, pi. vii. 
Abstract: Am. Geo]., vol. xiii, p. 428 (}p.). 
Describes the appendages attached to the pygidium or caudal shield 
of Triarthrus. 
