_ BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 
VOL. 9, PP. 257-268, PL. 18. MARCH 28, 1898 
WEATHERING OF ALNOITE IN MANHEIM, NEW YORK 
BY C. H. SMYTH, JR. 
(Presented before the Society December 29, 1897) 
CONTENTS 
Page 
Henin OCUC HLOM Mier tote cleo ce wi csle ne ce pace neerete aye ASS Eetan ori nner ene ne 257 
ILO GEMM - oo ciate era cie fed nee OIA Re eRe re ei rena aise int ae re og 258 
MD PeCARAMceOtnOcke mene Meld sss. secrete met acess esse et aes 258 
eT O OMAN NN AON GING SO CKSs tial aps ce sie Sls\a «2 acc alars iecmeore ms mec eeiee tase) bfevons Resth aiecatalgii shal: 260 
Sana olesmronmayinalipSlSteicie. <yeiteia cea eves weir) sie rare © aici Said atety eel dens cilia g euehstantea tie ar 261 
IRQSUULIS OF AMEN SE nea lo EO peo DRA Re I ee eA ie enemies tea 262 
DiscussionmotmeesulisyotamaliyseS: 225 o.:es sa). ss cele ciel n eee e let eee nee: 262 
Contrast betw«en weathering and alteration..................000.e epee eee 266 
Rate of decomposition of biotite...........0...... 2.0. c ee eee ee 266 
TNS. OF WIG ct SINCE ca hoc ee ae OM ees Gre ces oe e te eon aa een 267 
INTRODUCTION 
The importance of rock weathering is equally great, whether viewed 
from the purely scientific or from the economic standpoint. 
As the initial step in the processes of subaerial denudation and subse- 
quent deposition and in other relations, weathering demands the most 
serious consideration of geologists; while for a rational study of soils and 
of building stones, as well as for a thorough understanding of the condi- 
tions presented in the superficial portions of ore deposits, a knowledge of 
the principles of weathering is indispensable. 
This is exemplified by, to cite only a few instances, such papers as 
those of Pumpelly,* Reade,t Chamberlin and Salisbury,{ and Russell,§ 
*R. Pumpelly: The relation of secular rock-disintegration to loess, glacial drift, and rock basins. 
Am. Jour. Science (3), vol. xvii, p. 183. The relation of secular rock-disintegration to certain tran- 
Sitional crystalline schists. Bull. Geol. Soe. Am., vol. ii., p. 209. 
77. M. Reade: Chemical denudation in relation to geological time. Trans. Liverpool Geol. Ass., 
vol. iii., p. 211. Reprint, London, 1879. 
{T. C. Chamberlin and R. D. Salisbury: Preliminary report on the driftless area of the upper 
Mississippi valley. Sixth Annual Report U.S. Geol. Survey, p. 199. 
21. C. Russell: Subaerial decay of rocks. Bull. 52, U. 8. Geol. Survey, 
XXXIX—Bourr. Gzou. Soc. Am., Vou. 9, 1897 (257) 
