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190 T. S. Hunt—The Decay of Rocks. 
Art. XXIII. rhe: Decay of Rocks Geologically Considered ; by 
T. Srerry Hunt, LL.D., FBS. 
[Read before the National Academy of Sciences at Washington, April 17, 1883.] 
ConTENTS OF SEcTIONS.—1, 2, The supposed relation of rock-decay to climate ; 
; ios 
Whitney, Pumpelly and Dawson on decay of limestones ; 10, su vaérial proeens 
11, 12, Its antiquity and its relation to glacial erosion; 13, Decay in the Blue 
idge; Hunt, Burbank; 14, 15, Chemical significance of a 6 of aluminous sili- 
cates; 16, Analyses of decomposed feldspars; 17, 18, The question in relation to 
eozoie roc s; 19, Bowlders in crystalline schists 20, 21, Decayed gneiss of 
Hoosac Mountain; 22, Of the South Mountain, Penn; 23, At Atlanta, Ga.; 
density of decayed ‘rocks; 24-26, Deipritoriii vies 35 its decay; iron and copper 
_ ores; 27-30, Limonites of the Appalachian bong tertiary limonites (foot-note); 
31-34, Lesley, Jackson, Frazer and Lyman on limonites; 35, : B. Rogers 
on formation and segregation of siderite; 31, 38, imonites from serpelune of 
or. pone 39, Pumpelly on decay of gt esas aighen ie in ee its 
; 40 isse i 
Winchell and Irving; 41, Rock-decay ZA Sweden and % eee ae 42, Post-Cam- 
brian decay of i igneous rocks; 44, 45, Decay of auriferous gravels in sage wre 
influence of carbonic acid; 46, Sli ght oS in F oekaki cial times; effec 
changes of temperature y eoccenitey 47-49, Pumpelly on the geological pelagions of 
Fock-decay ; 50-52, Studies of Reusch j in Corsica: 53, Conclusions. 
§ 1. The subject of the decay of rocks has not yet received 
pic geologists all the attention which it merits, and there still 
in ee an some points in its history. Professor _ 
northern regions are supposed him to retard the action of 
atmospheric waters, regarded as the chemical agent of this pro- 
cess of decay.” These views, implying that the process is one 
nelonging | to the present time, are accepted b Professor Storer, 
who writes of the ‘‘ more active and ihorouah -going disintegra- 
tion which occurs” in these southern region 
§ 2. That the Seer in the northern hemisphere of a man- 
tle of softened material from the decay in situ of crystalline 
_ rocks is more onros at the oe of these 1 ie i than in 
high latitudes, where it is often entirely absent, is a iliar 
: et but it will, I think, be made evident that cireuelat climatic 
Gs 1 "Science, for February 16, 1883, p. 29. 
-? Bernay’s Hand-book of Reese 1878, p. 199. 
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