,oWa^ Jovwlaj jLuxaa
THE PHYSICAL GEOGRAPHY
GEOLOGY, MINERALOGY
AND PALEONTOLOGY
OF
ESSEX COUNTY, MASSACHUSETTS
JOHN HENRY SEARS
Curator of Geology, Mineralogy, and Botany
AT THE PeABODY MUSEUM,
Salem, Mass.
SALEM, MASS.
PUBLISHED BY THE ESSEX INSTITUTE
i9°5
QE
S4
Copyright, 1905, by
THE ESSEX INSTITUTE.
bosâ„¢ COLLEGE
, COMPLXMENTS OF
JOHN H. SEARS
GEOLOGY AND BOTANT
PEABODY MUSEUM.
SALEM, MASSACHUSETTS.
TO
DAVID PINGREE
THIS VOLUME IS DEDICATED IN
APPRECIATION OF HIS UNFLAGGING INTEREST
AND GENEROUS ASSISTANCE
PREFACE
Twelve years ago, at the request of the Trustees of the Peabody Acad-
emy of Science, I began work upon a preliminary map of the bed-rock of
Essex County, which was published in 1894 in the Bulletin of the Essex
Institute. In the meantime I prepared a number of short papers which
were also published in the Bulletin, under the general title of "Geological
and Mineralogical Notes." Since 1894, the work of mapping the out-
crops of bed-rock in the County has been continued and the superficial
deposits of sand, gravel, till, clay-beds, peat-deposits and silts have been
plotted with the greatest possible accuracy. With the exception of such
areas as are under water, every sixth of a mile in the entire County has been
examined several times by ranges running from east to west and also
from north to south. In the determination of the rocks, over eight hun-
dred thin sections have been prepared, the larger portion of which are
preserved, together with the rock specimens, in the cabinets of the
Peabody Museum. The results of this close examination of the surface
are presented in the following pages. The physical geography of the
County is described and much space has been devoted to the surface
features. The outcrops of bed-rock are superficially described in the
text, and at the end of the volume a map will be found on which the de-
posits of boulder-till, gravel-terraces, sand-plains and other features are
represented together with all outcrops of bed-rock. The points of the
compass indicated are according to the magnetic compass, its variation
from the true north in this region in 1898 being 12° 7' west.
To Dr. Henry S. Washington, of Locust, New Jersey, I am indebted
for chemical analyses of many of the rocks, especially those in the syenite
group. I also would acknowledge my obligations to Dr. William H. Dall,
of the United States Geological Survey, for assistance in determining the
5
6 PREFACE
leda marine clay fossils; to Prof. A. E. Verrill, of New Haven, Conn., for
identifying the starfish found in the marine clay at Lynn; to Mr. J. A.
Cushman, of the Boston Society of Natural History, for his excellent
drawings of fossils; to Prof. Charles D. Wolcott, Director of the United
States Geological Survey, for his assistance in naming several of the Cam-
brian fossils, and also for aid in the construction of the geological map ; and
to Mr. Richard A. Hale of Lawrence, Mr. John L. Gardner, 2d, of Boston,
and others, for photographs used in this voltmie. My thanks are also due
to Mr. John Robinson, of the Peabody Museum, for his interest and
early encouragement of my work; to Prof. Edward S. Morse, Director
of the Peabody Museum, for valuable advice in relation to the paleon-
tology of the County ; and to Mr. George Francis Dow, Secretary of the
Essex Institute, for assistance in revising my manuscript. Lastly, my
most grateful thanks are due to Mr. David Pingree, of Salem, without
whose generous aid this work would not have been accomplished. It is
also a pleasure to record my appreciation of the spirit of cooperation dis-
played by landowners and others in aU parts of the Cotmty, and my
thanks are also due to Mr. Woodbury Page Conant, of Salem, and Mr.
Joel Kimball, of Beverly, as well, who have accompanied me on many
long walks in out-of-the-way places and in the northern part of the
County.
CONTENTS
CHAPTER I. PAGE
Physical geography 21
Watersheds 21
Springs 22
Drainage and formation op valley systems 27
River systems 27
Surface features 34
Peat deposits 34
Geological distribution of plants 34
CHAPTER II.
Coast— line topography , . 45
Rocky headlands 45
Smooth or regular coast— lines 45
Drowned river valleys dub to subsidence 46
Subsidence 51
Sea beaches 58
Sand— dunes 62
Erosion of the shore by wave— action 68
CHAPTER III.
Outcrops of bed— rock 76
Stratified rocks of sedimentary origin 76
Metamorphism 76
Cambrian rocks 83
Hornblende epidote gneiss 90
Ancient rocks of sedimentary origin on Cape Ann 94
Slate or mica— schist 97
Sandstone 117
Limestone 121
CHAPTER IV.
The eruptive plutonic rocks 125
Quartz augite diorite 125
Hornblende diorite 129
CHAPTER V.
Hornblende granite 150
Micrographic granite 154
Porphyritic granite 166
CHAPTER VI.
Muscovite biotite granite 168
Paisanite 173
7
8 CONTENTS
CHAPTER VII. PAGE
The syenite rocks i77
The syenites of Salem Neck and vicinity 178
essexite 185
Salemite 186
Nepheline syenite 189
Quartz augite syenite or akbrite '. . . . 190
pulaskite 201
Nordmarkite 201
SoLVSBERGITB 202
BlOTITE TINGUAITE 205
AeGIRINE TINGUAITE OR ANALCITE TINGUAITE 2O9
Umptekite gabbro 210
Keratophyre 214
CHAPTER VIII.
Igneous volcanic rocks 222
CHAPTER IX.
The minerals op Essex County 230
CHAPTER X.
The quaternary pleistocene period, glacial ice epoch 253
Eskers 259
Evidences of sea beaches at inland points 272
Subglacial drumlins 277
Wash— plains 278
Kames and ice-block holes 283
Post-pleistocene sand and gravel 295
Drumlins carved by landslides 344
CHAPTER XI.
Clays 357
Residual clays 357
Upper clays 357
Manufactures of clay 358
Glacial marine or leda clays 363
Summary of subsidence and elevation .■• ■37°
Recession of the ice-sheet 373
CHAPTER XII.
Paleontology of the Cambrian rocks 380
APPENDIX A. Surface areas 393
APPENDIX B. Elevations of drumlins 395
APPENDIX C. Elevations of bed-rock hills 399
APPENDIX D. Lakes and ponds in the county 400
APPENDIX E. Geological succession of the rock formations 402
APPENDIX F. Chemical analysis of the rocks 404
APPENDIX G. Bibliography 40S
Map of Essex County, showing geological outcrop, etc In Pocket
LIST OF ILLUSTRATIONS
Page
Pig. I. Portrait of the author Frontispiece
Fig. 2. Merrimac river at the Lawrence dam. Winter of 1897. Photograph
by Richard A. Hale 20
Fig. 3. Merrimac river at the Lawrence dam, during the spring freshet.
Photograph by Richard A. Hale 20
Fig. 4. Merrimac river at Mitchell's falls, during low water, October 3, 1897.
Photograph by Richard A. Hale 24
Fig. 5. Merrimac river at Mitchell's falls, during low water, 1897. Kim-
ball's island at the right. Photograph by Richard A. Hale ... 24
Fig. 6. Mouth of the Spicket river, Lawrence. Photograph by Richard A.
Hale 26
Fig. 7. Spicket river below the Globe Mills dam, Lawrence. Photograph
by Richard A. Hale 26
Fig. 8. Ipswich river at the Middleton Paper Mill dam 30
Fig. 9. Ipswich river in Middleton, as seen from the bridge on the Danvers
road ^o
Fig. 10. Ideal vertical-section across Essex County, showing sections of the
eruptive, volcanic and sedimentary rocks 32
Fig. II. Chestnut trees (Castanea Americana) growing upon hornblende
granite soil on the Burley Farm, Danvers 36
Fig. 12. Bedded slates and limestones at East point, Nahant 38
Fig. 13. Hornblende granite headland at Eastern point, Gloucester. Photo-
graph by Babson 38
Fig. 14. Gap Head and Straitsmouth island, Rockport, showing an augite
syenite contact with hornblende granite 42
Fig. 15. Squam river from West Gloucester, showing tidal marshes. Photo-
graph by John L. Gardner, 2d 42
Fig. 16. Tidal marsh at Rowley. View from the railroad at high tide, Plum
island in the distance 44
Fig. 17. Lagoon, west of Jeffrey's Neck, Ipswich, showing tidal marsh, and
drumlins in the distance 44
9
10 LIST OF ILLUSTRATIONS
Page
Fig. i8. Parker river below the Byfield Woolen Mills, at low tide 48
Fig. 19. Parker river below the Byfield Woolen Mills, at high tide 48
Fig. 20. Saugus river marshes at high tide, showing drowned topography
due to subsidence 50
Fig. 21. Saugus river marshes at high tide, from the Lynn and Boston turn-
pike, looking towards Lynn 50
Fig. 22. Waters river, Danversport, at low tide, the Beverly shore in the
distance 54
Fig. 23. Crane river, Danversport, at nearly low tide, showing the meander-
ing of the stream 54
Fig. 24. Forest river, Salem, at low tide. Jeggles' island in the foreground
and Legg's hill in the distance 56
Fig. 25. Forest river, Salem, above the dam, at low tide; from Legg's hill . . 56
Fig. 26. Mingo beach, Beverly (1894), showing submerged peat-beds, and
logs and stumps of forest trees 60
Fig. 27. Pond beach, Nahant (1894), showing submerged stumps of white
pine trees 60
Fig. 28. Ideal section of a sea beach, of which Plum island beach is a type . 64
Fig. 29. Ideal section of Ipswich beach 64
Fig. 30. Off-shore bar at Ipswich beach, showing cuspated foreland and
lagoon 66
Fig. 31. Ipswich beach from the top of Castle hill, showing cuspated fore-
land and off-shore bar 66
Fig. 32. View from Gale's point, Manchester, at low tide, showing the follow-
ing islands: House, Misery, Ram, Baker's, Eagle, and Lowell . . 70
Fig. 33. Coffin's beach, West Gloucester, from Black Rocks to the Loaf,
showing ripple marks and cuspated drifting of sand. Ipswich
beach and Plum island in the distance 70
Fig. 34. Coffin's beach, West Gloucester, showing sand-dunes of Post-
Pleistocene drift-sand 72
Fig. 35. Post-Pleistocene wind-blown sand-dune at Castle Neck, Ipswich,
showing stratification of the sand 72
Fig. 36. Ideal cross-section from Hog island, Essex, to Ipswich beach ... 74
Fig. 37. Post-Pleistocene wind-blown sand overwhelming an apple orchard
on the Lakeman farm. Castle Neck, Ipswich 74
Fig. 38. Sand-spit oft Castle Neck, Ipswich, as seen from Hog island, looking
across Castle river . -. 78
Fig. 39. Continuation of the sand-spit off Castle Neck, Ipswich, as seen from
Hog island. Glacial drift boulders appear in the foreground . . 78
Fig.
41-
Fig.
42.
Fig.
43-
Fig.
44.
Fig.
45-
Fig.
46.
LIST OF ILLUSTRATIONS 11
Page
Fig. 40. Sand-dimes on a rocky headland near Coffin's beach, West Glouces-
ter. Photograph by John L. Gardner, 2d 80
Sand-dunes south of Coffin's beach, West Gloucester 80
Kame ridge on south bank of Castle river, north of Hog island,
Essex. Ipswich lighthouse and Plum island in the distance at
the left 82
Barrier beach between Clifton and Marblehead Neck (July, 1895),
showing sea- worn pebbles washed into windrows by the tides . . 82
Ideal vertical-section across Salem harbor, showing existing strata
of Cambrian rocks 86
Hornblende epidote gneiss cut by a coarse hornblende granite.
Crooked pond, Boxford 88
Inclusion of hornblende epidote gneiss in foliated quartz hornblende
diorite. A narrow vein of the diorite cuts through the gneiss
upon which the watch is resting. Southeast of Crooked pond,
Boxford 88
Fig. 47. Photomicrograph of hornblende epidote gneiss. Crooked pond,
Boxford 92
Fig. 48. Cave in ledge of quartz hornblende diorite east of Crooked pond,
Boxford 92
Fig. 49. Merrimac river flowing under the Chain bridge at Newburyport.
Quartz diorite rock on both sides of the river 96
Fig. 50. Cambrian slaty sandstone ledge at South Lawrence, used (1901) for
road material 96
Photomicrograph of schiefierhomfels. West cove. Misery island . . 100
Photomicrograph of quartzite sandstone. South Georgetown. ... 100
Cambrian limestone and chert. East point, Nahant 104
Cambrian limestone and chert cut by a massive basalt dyke. North
of Pulpit rock. East point, Nahant 104
Hornblende diorite ledge on the Pickman estate. South Salem . . 108
Hornblende diorite ledge in process of removal by the Massachu-
setts Broken Stone Company (1898), Castle hill, Salem 108
Hornblende diorite outcrop in the "Nubble Squid," Groveland . . 112
Split boulder of hornblende diorite near the "Nubble Squid," Grove-
land 112
Devil's den, Newbury, showing limestone and serpentine in the
foreground 116
Devil's den, Newbury, showing a quartz hornblende diorite forma-
tion 116
Fig.
SI-
Fig.
52-
Fig.
S3-
Fig.
54.
Fig.
55-
Fig.
56.
Fig.
S7-
Fig.
58-
Fig.
S9-
Fig.
60.
12 LIST OF ILLUSTRATIONS
Page
Fig. 6i. Stickney boulder, Groveland. A hornblende diorite rock resting
upon an outcropping ledge of hornblende diorite 120
Fig. 62. Split boulder of hornblende diorite, near the Stickney boulder. Grove-
land 120
Fig. 63. Norseman's rock, a quartz hornblende diorite outcrop in West
Newbury 124
Fig. 64. Cradle rock, Groveland, a glacial perched boulder of diorite, resting
upon an outcropping ledge of diorite 124
Fig. 65. Ordway boulder, Byfield, a glacial erratic of foliated quartz horn-
blende diorite 128
Fig. 66. Haystack boulder, Newbury. A glacial erratic of quartz horn-
blende diorite, probably removed from the ledge six hvmdred feet
distant at the north 128
Fig. 67. A glacial erratic boulder of quartz augite diorite located a short
distance from the Haystack boulder, Newbury. Length, 28* feet
and width, 18 feet. Upper surface is well glaciated. The nearest
outcrop of this formation in the line of glaciation is at Amesbury. 132
Fig. 68. Foliated granite with inclusions of quartz diorite, at the base of
Long hill, Boxford 132
Fig. 69. Massive and foliated quartz hornblende diorite outcrop with intru-
sions of coarse vein-granite. Lovering's mountain, Boxford . . 136
Fig. 70. Hornblende diorite at Ledge Hill park, Salem, showing glaciated
surface 136
Fig. 71. Photomicrograph of white limestone, showing serpentine pseudo-
morphs. Devil's den, Newbury 140
Fig. 72. Photomicrograph of a biotite concretion in mica hornblende diorite
at Middleton 140
Fig. 73. Legg's hill, Salem, a diorite ledge with summit glaciated and stripped
of debris. Kame topography and washed gravels shown in the
foreground i44
Fig. 74. Quartz hornblende diorite outcrop at Clifton, showing broken and
bizarre form of headland 144
Fig. 75. Hornblende granite quarry at Rockport, showing jointing of the
formation 148
Fig. 76. Hornblende granite quarry at Lanesville, Gloucester, showing grad-
ual increase in thickness of the joint planes 148
Fig. 77. Raccoon rocks, Manchester, an outcropping ridge of hornblende
granite 152
Fig. 78. Hornblende granite outcrop in the Raccoon rocks, Manchester . . 152
Fig.
80.
Fig.
81.
Fig.
82.
Fig.
83-
Fig.
84.
Fig.
85-
Fig.
86.
Fig.
87.
Fig.
88.
Fig.
8q.
LIST OF ILLUSTRATIONS 13
Page
Fig. 79. Hornblende granite outcrops, between which a basic dike rock has
been removed by disintegration. South from Coffin's beach,
West Gloucester 156
Hornblende granite boulder at Essex, 32 feet high, 35 feet wide, 40
feet long; estimated weight, 3,763 tons 156
Photomicrograph of actinolite in a mass of Fayalite, Rockport . . 160
Photomicrograph of biotite olivin peridotite, Skug river, Andover . 160
Muscovite biotite granite, foliated, Jones quarry. South Lawrence . 164
Aplitic granite dike cutting quartz hornblende diorite, at Clifton,
Marblehead 164
Granitic white gneiss arkose, Jones quarry, West Andover .... 170
Granitic white gneiss, with much muscovite, Jones quarry. South
Lawrence 170
Quartz augite syenite, Poorhouse hill, Beverly 176
Augite syenite, Dudley L. Pickman estate, Beverly Cove 176
Brecciated hornblende diorite cut by veins of pulaskite syenite, near
Beverly bridge, Salem 180
Fig. 90. Hornblende diorite cut by veins of pulaskite syenite and diabase,
near Beverly bridge, Salem 180
Fig. 91. Salemite, on the south side of Fort avenue, Salem Neck 184
Fig. 92. Essexite, cut by veins of pulaskite syenite and camptonite, north
side of Fort avenue, Salem Neck 184
Fig. 93. Photomicrograph of Essexite from Salem Neck 188
Fig. 94. Photomicrograph of Salemite from Salem Neck 188
Fig. 95. Biotite tinguaite dike in augite syenite ledge, Manchester 192
Fig. 96. Nepheline syenite with veins of pulaskite and hornblende gabbro
and also showing erosion of boulders in situ. Cat cove, Salem
Neck 192
Fig. 97. Photomicrograph of augite syenite, or akerite. South Salem .... 196
Fig. 98. Photomicrograph of microcline in augite syenite from Briscoe hill,
Beverly, showing albite intergrowths across the twinned micro-
cline 196
Fig. 99. Pulaskite syenite formed into boulders in situ by disintegration and
erosion, Salem Neck 200
Fig. 100. Pulaskite syenite veins cutting decayed hornblende gabbro,
Salem Neck 200
Fig. ioi. Nordmarkite ledge broken down by action of frost. West Glouces-
ter 204
14 LIST OF ILLUSTRATIONS
Page
Fig. 1 02. Quarry opened in a ledge of nordmarkite, showing irregular jointing
of the rock, West Gloucester 204
Fig. 103. Photomicrograph of nordmarkite, Gloucester 208
Fig. 104. Photomicrograph of aegirine tinguaite from Pickard's point, Man-
chester 208
Fig. 105. Photomicrograph of aegirine syenite from Gale's point, Manchester,
showing the aegirine crystals arranged in a plane with ortho-
clase 2^2
Fig. 106. Photomicrograph of aegirine syenite from Gale's point, Manchester 212
Fig. 107. Salemite outcrop (in the foreground) and ledge of umptekite gab-
bro (beyond the road), Salem Neck 216
Fig. 108. Umptekite gabbro cut by veins of pulaskite syenite, Salem Neck . 216
Fig. 109. Photomicrograph of hornblende umptekite gabbro from Salem
Neck 22°
Fig. 1 10. Photomicrograph of umptekite gabbro from eastern side of Misery
island 220
Fig. III. Keratophyre from the harbor side of Marblehead Neck. Anor-
thoclase crystals appear as white spots 224
Fig. 112. Foliated aporhyolite, from a bare ledge off Marblehead Neck
showing weathered surface 224
Fig. 113. Photomicrograph of an anorthoclase crystal in keratophyre from
Marblehead Neck 228
Fig. 114. Photomicrograph of an anorthoclase crystal in keratophyre from
Marblehead Neck 228
Fig. 115. Castle hill, Saugus, a massive outcrop of aporhyolite, an ancient
volcanic rock 232
Fig. 116. Castle hill, Saugus 232
Fig. 117. Photomicrograph of liparite, a quartz porphyry aporhyolite with
spherulites 236
Fig. 118. Aporhyolite outcrop on the harbor side of Marblehead Neck, show-
ing the flow of the lava 236
Fig. 119. Aporhyolite, showing weathered surface. High rock, Marblehead
Neck 240
Fig. 120. Banded aporhyolite, showing the flow of the magma previous to
its consolidation, Bowden's point, Marblehead Neck 240
PiG. 121. Aporhyolite concretion, Marblehead Neck 244
Fig. 122. Aporhyolite conglomerate. South Gooseberry island, Salem harbor 244
Fig. 123. The minerals of Essex County, as exhibited at the Peabody
Museum, Salem 248
LIST OF ILLUSTRATIONS 15
Page
Fig. 124. View in Topsfield looking across the geographical center of Essex
County showing the even sky-line and roiinded outlines of the
surface. The Ipswich river is seen in the center of the picture
and the drumlins, Hunslow hill and Prospect hill are outlined
against the sky 252
Fig. 125. Quarry of the Rockport Granite Company at Rockport, showing
the general structvu^e of the hornblende granite rock 256
Fig. 126. Glaciated stones found in boulder-till at North Andover .... 256
Fig. 127. Glaciated diabase dike rock near Flying point, Marblehead Neck . 258
Fig. 128. Remarkable glacial groove, 30 feet long, 3 feet wide and sJ inches
deep, on the surface of a hornblende diorite ledge in Ledge Hill
park, Salem 258
Fig. 129. " Sheep backs " or roc/ies woMtowwm, at South Georgetown. Small
elevations of bed-rock covered by drift gravels 262
Fig. 130. "Sugar-loaf" hill or roche moutonnSe at Tops&eid. Arkose granite
conglomerate covered by a thin coating of glacial drift .... 262
Fig. 131. Ideal section of an ice-block hole 264
Fig. 132. Ideal section of an alluvial plain bordering the front of a glacier . 264
Fig. 133. The long esker near Dodge street. North Beverly 268
Fig. 134. The long esker near Dodge street, North Beverly. View looking
northwesterly across Dodge street 268
Fig. 135. Serpentine esker at Willowdale in Hamilton 270
Fig. 136. Bishop's swamp, Danvers, an ice-block hole. View from the base
of Nichols' hill, showing the gravels deposited from the surface of
glacial ice 270
Fig. 137. Serpentine esker on the Gwinn farm near Willowdale in Hamilton 274
Fig. 138. Serpentine esker at Willowdale in Hamilton, illustrating reticulated
kames, and knob and basin topography 274
Fig. 139. Norwood's pond. North Beverly, having esker terraces on both sides.
View from the main terrace 276
Fig. 140. Double-terrace esker on the north side of Longham brook, Wen-
ham, showing a kettle hole 276
Fig. 141. Kames and kettle holes near Forest river, Salem 280
Fig. 142. Steep-sided esker west of Norwood's pond. North Beverly .... 280
Fig. 143. Knob and basin topography, showing kettle holes southwest of the
"dungeons" in Marblehead 282
Fig. 144. Glacial till and gravel cone on the south side of Forest river, Salem 282
Fig. 145. Hog island, Essex, at low tide, a typical drumlin showing ado-
lescent grass-grown scarps caused by landslides 286
16
Fig.
146.
Fig.
147-
Fig.
148.
Fig.
149.
Fig.
ISO-
Fig.
151-
Fig.
152-
Fig.
153-
Fig.
IS4-
Fig.
iSS-
Fig.
156.
Fig.
157-
Fig. 158.
Fig. 159.
Fig. 160.
Fig. 161.
Fig. 162.
Fig. 163.
Fig. 164.
Fig. 165.
Fig. 166.
Fig. 167.
LIST OF ILLUSTRATIONS
Page
Mussey hill, Rowley, as seen from the rolling sand-plain towards
the southwest 286
Old Town hill, Newbury. View from the southwest across the
tidal marsh 288
Eagle hill, Ipswich, a small drumlin, with base cut by wave action 288
Hog island, Essex, at high tide, the rocks in the foreground are the
remnants of a stone wall on either side of a road which has been
submerged because of subsidence 292
Great hill, Haverhill, as seen from Whittier's hill 292
Drumlins on Jeffrey's Neck, Ipswich, as seen from Eagle hill ... 294
Turkey hill, a drumlin at East Haverhill 294
Whittier's hill, a drumlin at Haverhill 298
Ice-berg or kettle hole, in the "dungeons," Marblehead 298
Ice-berg holes in kame gravels near Legg's hill, South Salem.
Legg's hill, a wave-swept outcrop of hornblende diorite, may be
seen in the distance 300
Ice-berg hole in over-wash gravels, also showing a short kame
within the hole. The "dungeons," Marblehead 300
Over-wash gravels, ice-berg holes, and short reticulated kames.
Winter scene at the "dungeons, " Marblehead. Legg's hill at the
left 304
Winter scene at the "dungeons," Marblehead. Legg's hill at the
right 304
Legg's Hill pond, Salem. An ice-block hole nearly filled by peat 306
Crooked pond, Boxford. An ice-block hole which has become a
nearly filled pond 306
Ice-berg hole in an out-wash sand-plain, east of Wenham swamp.
Arbor street, Wenham 310
Ice-berg hole on the east side of Arbor street, Wenham 310
Kame terrace, marking an ice contact on the southeastern shore
of Leach's swamp, an ice-block hole. West Wenham 312
Another view of the above 312
Wenham lake. The tree-covered point at the left • is a gravel
terrace marking an ice contact 316
Drainage crease above a landslide on the southwestern side of
Hog island, Essex 3^6
Inland sand-dunes at East Georgetown near the Byfield meeting-
house 31S
LIST OF ILLUSTRATIONS 17
Page
Fig. i68. Another view of the above 318
Fig. 169. Cross-section of a terrace at High street, Newburyport 322
Fig. 170. Glacial groove in a quartz diorite ledge on the east side of Green
street, Newbury 322
Fig. 171. Merrimac river. The bend below Mitchell's falls, showing deposits
of river silts. Kame gravels in the foreground 324
Fig. 172. Enclosed block of ferruginous gravel probably deposited in a mass
during late glacial times. Sand-plain east of railroad station,
Hampton, N. H 324
Fig. 173. Merrimac river at Mitchell's falls. Lone Tree hill, Methuen, in
distance 326
Fig. 174. Ship rock, Peabody. An erratic boulder of hornblende granite . 326
Fig. 175. Hornblende granite boulder perched upon boulders eroded in
situ, Peabody. Photograph by Richards B. Mackintosh . . . 330
Fig. 176. Hornblende granite boulders eroded in situ, Peabody. Photo-
graph by Richards B. Mackintosh 330
Fig. 177. Hornblende granite ledge at Peabody, showing horizontal jointing.