124 The American Geolorjisf. February, 1895 
colored bands hriii^- ricli in IVldspai', and thi' darker licli in tiie lerro- 
magnesian constituents and maynelite. Tiiere is iioessential dilference 
between the different hands as regards coarseness of grain, and*tlie in- 
dividual minerals interlock with each other across a junction line just 
as they do in the central portions of the bands. It therefore seems im- 
possible to account for the banding by the successive injection of mag- 
mas of varying composition, and, as cataclastic phenomena have not 
been observed, the authors concludi' that the cause which produced the 
banding must have operated before tlu; crystallization of the minerals. 
They consider the banding as the result of a heterogeneous magma. The 
analogy between these banded structures in the deep-seated basic rocks 
and some of tlie bandings in the ancient gneisses, especially the Lewis- 
ian gneiss of northwestern Scotland, is clearly pointed out, and it is 
shown that the causes which produced the former may justly be con- 
sidered as applicable to the latter. "In view, however, of the undoubted 
evidence of secondary dynamic action in many regions, and in the ab- 
sence at present of any well established criteria by which we can in all 
cases discriminate between original and secondary structures, we are 
not yet in a position to define the exact limits within which the hypoth- 
esis of the intrusion of heterogeneous magmas is ap])licable to the ex- 
planation of the Lewisian gneiss." 
This paper presents one of the many facts which, in recent years, have 
led most geologists to conclude that many of the parallel structures in 
the ancient gneisses are not necessarily due to original sedimentary 
deposition, but can be e\i)lained equalh' well, or better, on other hy- 
potheses; still, there remain some who find it difficult to consider band- 
ing in gnei.sses as anything but good evidence of a sedimentary origin 
for these rocks. v. s. <;. 
RECENT PUBLICATIONS. 
/. Government uikI St((te Report, s. 
Proc. U. S. Nat. Miis., vol. 17, No. 1002. Discovery of the giMius Old- 
hamia in America, C. D, Walcott. 
Geol. Sur. of Alabama, Eugene A. Smith, State (Geologist. Geological 
map of xMabama, with explanatory chart, 1894. 
Bull. No. T), Illinois State Mus. Nat. Hist. New genera and species of 
Echinodermata, S. A. Miller and Wm. F. E. Gurley, 53 pp..r)i)ls., Dec. 
20, 1894. 
//. Proceedutyn of Scientific Societies. 
Proc. Boston Soc. Nat. Hist., vol. 2(5, pts. 2-3, 1894, contains: Facetted 
pebbles on Cape Cod, Mass., W. M. Djivis: Some typical eskers of south- 
ern New England, ,T. B. Woodworth: On the distribution of earthquakes 
in the United States since the close of the Glacial period, N. S. Shaler: 
The geographical development of alluvial river terraces, R. E. Dodge; 
The preglacial channel t)f the Genesee river, A. W. Grabau; A speci- 
