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GRESLEY : 
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ILLUSTRATIONS. 
Plate 27—Hoprktys: Shale exposures on the Ohio river bluff opposite Beaver, 
showing concentric weathering (2 figures)............. 
2 Rock cut on the Pittsburg, Fort Wayne and Chicago rail- 
road a quarter of a mile east of Rochester, Pennsylvania, 
showing concentric weathering in the shale........... 
Concentric weathering in shale and fire clay of Pennsy]- 
Vania: (2 figures)is. ss: sesraeeerteas: 8. Stzauyetne ay Mlousie ete sai 
FIGURES 
1—Section along the Mexican railway .....,................- 
2—Section between Saltillo and Monterey. .. ................ 
3—section along Rio Sam Geronimo......-................-. 
A Sechiomat Cha varillo vee epeemris vtec cies | uteri 4 em ars oolenen 
5—Section between Solidad and the mountains.. . .......... 
6—Junction of the Columbia and Lafayette formations........ 
1—Vertical section of ordinary clay-vein........ Gece arene 
B= s\V Oral UO eA CS cc ot 3 0-6 6 SERRE eG Ie are ae 
S—= Win Routt, Vos peanee asc LAOS 6c GER Bete SRI cree eee na mins 
4— (Coal pierced by clay-vein material................ ........ 
45—Distribution of clay-veins as observed in coal seams of the 
UO pMHbeSCS tates < . .\ creamery etna te Specie lcs eee aie 
6— Plan of clay-veins in the Pacific mine..................... 
7—Plan of part of most prominent clay-vein in the Florence mine. 
8—Displacement of coal bed by clay-vein............. 
9—Disturbance of coal bed by clay-vein................ ..... 
= Piecevotmyein- til limeycoaleemere i.e nce sis eyre 
Het Sp ASmel CO], | Aseria Sci sd ioc aiesaituetcapsae Seenos hau: j 
1P—impecse! oat DNS, 25k Mc oo dab eedeooeBecasoscuDT anaes 
e==Mlowaceolclay-Velmemeweeeiy. sce sss bees a os eran k 
jae Noduilespimyclay- Vel rmmeney ee ac (asirne e ape pA oaeel), ee 
15—Fossils from nodules in clay-veim...... ..........-......0. 
16—Diagram illustrating trend of clay-veins and their relation to 
‘onnerspliysical) featlinesmeemi ss seca Seer AINA oe 
17— Vertical section in mine at Buena Vista................... 
18—Plan of shale masses in ‘* Block House”’ coal seam......... 
19—Vertical section of shale masses in ‘‘ Block House’’ coal seam. 
20—Section in the ‘‘ Main”’ coal of Leicestershire, England... 
21—Forked! clay-veins................... cris niall NU G clorm eyene 
DP ClonmlonmAiO ON AWOINE, ..ccssdooccodosscoccgenvoosds sens 
23—Section of clay-vein in the “ Little’”’ coal of Derbyshire.... 
24—Section in a tunnel at Moira, Leicestershire... .. Nc expe 
25— Vertical section in the “ Lount Middle” coal bed of Leicester- 
FSI SUN RS Sh RON 3 < c-o9. 2 RR arene eee ARE AURA TEs ete 
26—Section of clay-vein in Sprinefield colliery................. 
27—Section of clay-vein near Beaver falls...................... 
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