USA > New Hampshire > Grafton County > Hanover > Hanover, New Hampshire, a bicentennial book : essays in celebration of the town's 200th anniversary > Part 3
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How did the bedrock form, and how far back can we trace its history? Four hundred and fifty million years ago, all of New Eng- land was an arm of the Atlantic. The ocean, at that time, had its western shore-line near the present Adirondacks and the upper St. Lawrence Valley. At the site of Hanover, black muds, volcanic rocks, and sands gradually accumulated in great layers over the ocean floor during an interval of at least 75 million years. As sedimentation progressed the ocean bottom gradually subsided, and a 25,000 to 40,000-foot blanket of detritus was amassed.
This process of marine sedimentation was terminated, approxi- mately 375 million years ago, when the earth's crust throughout northern New England was crumpled, and temporarily elevated above sea level. Here and there small bodies of molten granite
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Hanover Bicentennial Book
worked their way upward from deeper levels within the earth, shouldering aside the bedrock, and reaching positions where they eventually congealed. One of these granites is now exposed a half mile west of White River Junction; another holds up the cliffs at Fairlee, Vermont.
Hanover's first episode of continental existence lasted for only a few millions of years. The newly emerged land was soon reduced by erosion, and the sea once more encroached over New England. The first sediment deposited on the ocean floor by this new marine advance was a layer of quartz sand and quartz pebbles, on the aver- age 50 to 200 feet thick. This material has subsequently been transformed into the hard, resistant quartzite whose outcropping now forms the backbone of Moose Mountain.
Following the cycle of sand and pebble deposition, the ocean over New England became warm, shallow and clear. In this hos- pitable environment, corals, shellfish and other marine organisms flourished, much as they do in present-day subtropical oceans. Simultaneously a succession of limestones was deposited on top of the sand and pebble beds. Some of the limestone beds consisted almost wholly of shell accumulations, but the deposit as a whole was very thin, and none of it is preserved, unfortunately, within the limits of Hanover.
The interval of limestone deposition was followed by one in which the ocean floor received an increasing quantity of black mud, which eventually accumulated during a 20-million year in- terval, to a thickness of 10,000 feet. Then a second cycle of crustal upheaval, more violent than the first, again gripped New Eng- land, permanently elevating the entire area above sea level. The region was squeezed as though in a gigantic vise, and the rocks were crumpled into tight north-northeasterly trending folds. In the area about Hanover the rocks were also heated to tempera- tures of 700 to 800 degrees Fahrenheit. As a consequence, and also because they were being simultaneously deformed, the original rocks laid down on the ocean floor were transformed or metamor- phosed into green amphibole schists (formerly volcanic ash beds or lava flows), black schists (formerly black muds) or quartzites (formerly sands); these are the rocks which now underlie much of Hanover.
Toward the close of this major cataclysm, molten granite once more worked its way upward from the deeper levels of the earth. Two great bulbous masses rose into the Hanover area, both of
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The Town's Prehistory
them punching their way upward while arching and draping the metamorphic rocks over their roofs. From recently determined radioactive age measurements we know that this event occurred 310 million years ago; this is the age of our youngest extensive bedrock formations-the Lebanon and Mascoma granites.
The structural framework of Hanover was thus complete, with a minor exception. A few 10- to 20-foot wide sheets of magma forced their way upward 180 million years ago, and solidified as trap dikes. These rocks, however, are rare; the best exposed dike trends east-west for a mile and a half across the countryside about midway between Etna and Hanover Center.
For more than 300 million years, and until the recent past, the only significant event in Hanover's slow evolution has been the etching of the landscape by erosion. All in all, a thickness of at least four miles of bedrock has been slowly peeled away. In the process, the harder and more resistant rocks have gradually emerged above their surroundings. Thus Balch Hill and Velvet Rocks, underlain by Lebanon granite, rise 400 feet above the gen- eral level of the amphibole schists which wrap around the granite on the west. Moose Mountain, underlain by hard quartzite, rises 800 feet above the average elevation of the less resistant black schists forming the bedrock east of Etna. By the time of the Pleis- tocene glaciation, the topography east of the town had achieved much of its present essential outlines.
The Pleistocene ice ages, which commenced a half-million years ago, were marked by four cycles of accretion and subsequent wastage of continental glaciers. Focal points of maximum glacier growth were in the Hudson Bay region and in Labrador, and the ice spread unevenly southward from these centers on at least four separate occasions. Only during the last, or Wisconsin, advance did the glaciers reach New England, and then in such great vol- ume as to completely overwhelm the land, burying the White Mountains, and extending as far south as the present site of Long Island. Thus, no more than 20,000 to 25,000 years ago, Hanover lay buried beneath at least a mile thickness of ice.
A continental glacier functions much like a bulldozer, scraping up the alluvium and loose rock caught in its path, churning them about as it continues its slow, relentless advance, and eventually spreading a rubble of intermixed clay and boulders over the countryside. Such a mass of till has been plastered over the local terrain, obscuring the bedrock over most of the area lying above
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Hanover Bicentennial Book
the general level of the Hanover plain. Some of the boulders in this till originated hundreds of miles to the north, in Canada; others are of more local origin. Here and there beneath the till, especially on freshly uncovered outcrops, are gouges and striae left on the bedrock by boulders dragged along under the ice cap. Hayes Hill east of Etna abounds in such vestiges of the vanished glacier.
The evolution of the Hanover plain belongs to a segment of late-glacial history. Following the glacial climax, New England was slowly uncovered as the ice wasted down and retreated north- ward. According to Lougee and Antevs, who have studied the glacial geology of the Connecticut Valley, natural till dams were left behind at several places as the ice melted away, notably near East Haddam, Connecticut. Glacial meltwaters pouring down the valley were impounded behind this dam, and as the ice slowly re- treated northward, the dammed water spread in the same direc- tion, eventually inundating Hanover, and extending for 160 miles up the Connecticut Valley to near Lyme, New Hampshire. Lougee has called this great body of water Lake Hitchcock. A somewhat younger and lower stage of this lake, extending from the Massa- chusetts line to beyond St. Johnsbury, Vermont, has been termed Lake Upham.
Glacial meltwater streams, flowing either in crevasses on the ice or in tunnels beneath it, transport large volumes of coarse gravel. When the ice has disappeared from a region the sites of these former stream channels are marked by sinuous gravel ridges, termed eskers. Such an esker may be traced discontinuously for twenty-four miles from Thetford to Windsor, Vermont. The esker crosses the Connecticut and enters Hanover just south of the mouth of Camp Brook. It forms Occom Ridge and River Ridge, and continues southward for two-thirds of a mile below the town line, where it again recrosses the river near Wilder, Vermont. This fortuitous coincidence of geology and geography has given the town its most valuable mineral resource-several million cubic yards of gravel.
The esker, when first formed, stood as high as 150 feet above the ground on either side. It was soon immersed, however, in the waters of Lakes Hitchcock and Upham, and almost buried by the deposits formed in those lakes.
The sediments which were deposited in Lakes Hitchcock and Upham are of two varieties, deltaic gravels and varved (banded)
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The Town's Prehistory
silts. It is a well-established, easily-observable fact that the topmost beds of deltas form at, or very close to water level. Two delta de- posits recognizable in Hanover, one with an elevation of 657 feet at Cutting Corner, south of Etna, and the other with an elevation of 565 feet at Sand Hill, are taken by Lougee to represent the respective water levels of Lakes Hitchcock and Upham. This would imply, during the life of Lake Hitchcock, a depth of more than 130 feet of water at the present site of Hanover plain, and a depth of more than thirty-five feet of water during the life of Lake Upham.
Varved silt, the other type of sediment which formed in these glacial lakes, is exposed in almost every excavation on the Han- over plain, and in a classic locality at the cutbank on Mink Brook, immediately south of the town. The varved silts have a maximum thickness of 140 feet at Hanover, but an average thickness con- siderably less than this. It is thought by some geologists that the varves represent seasonal deposits, the tan silt layers corresponding to material brought in during the spring and early summer floods, and the gray layers representing the fall deposits, with their higher content of clayey and carbonaceous material. Thus a light and dark band-a varve-may be interpreted as a year's deposit of silt. At the Mink Brook cut there are fifty varves from the bottom of the brook up to a height of forty feet above the stream bed. This is succeeded by a layer of sand, twenty-one feet thick, and then by 600 thin varves. The exposure has been interpreted by Lougee and Antevs as indicating fifty years in the history of Lake Hitch- cock, an interruption (represented by the sand) during which the lake level was being rapidly lowered, and a succeeding interval of 600 years in the life of Lake Upham.
Varves vary in thickness, probably because of climatological fac- tors. It is possible, in clay pits or exposures which are not sepa- rated by more than a few miles, to find corresponding variations in the relative thicknesses of the varve layers. However, the rela- tive position of a varve representing a given year's deposit may vary from pit to pit. For example, one of the lowest varves in a pit at Piermont apparently correlates with a varve which is number 151 from the bottom in a pit at West Lebanon. This correlation can only mean that there was glacial ice but no lake at Piermont at the time varves commenced to form at West Lebanon. Evi- dently it took 150 years for the ice front to retreat the twenty- seven miles between these two points. The glacial lake pre-
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Hanover Bicentennial Book
sumably spread northward between these two points at an average rate of approximately 900 feet per year. Using evidence such as this, and on the basis of a study of numerous clay pits between St. Johnsbury, Vermont and Hartford, Connecticut, Antevs has con- cluded that it required almost 4,000 years for Lake Hitchcock to spread from Hartford, Connecticut, as far north as Lyme, New Hampshire, and that Lake Upham, which eventually reached as far north as East Burke, Vermont, lasted for an additional 600 years. According to our best estimate, these events occurred some- where in the interval between 17,000 and 11,000 years ago.
At the time the impounded meltwaters were eventually released from Lake Upham, all of Hanover west of Balch Hill and Velvet Rocks was a featureless plain. As the Connecticut reestablished its course, however, it cut down rapidly through the soft lake silts. Tributaries such as Mink, Girl, and Camp Brooks again be- came active, sluicing out thousands of tons of silt, and producing the gullied topography of the present town. The process still goes on, but at a reduced rate; it will continue until, thousands of years hence, Hanover is reduced to the general level of the Con- necticut.
Some of the post-glacial drainage features of Hanover merit further brief comment. It was pointed out by Goldthwait, thirty years ago, that Girl Brook and Mink Brook have cut well-de- veloped terraces and now-abandoned stream meander scars high above their present stream channels. These terraces are small-scale duplications of the larger terraces so conspicuous along both banks of the Connecticut throughout most of its course. What is their significance and history? It is probable that most of the terraces along the Connecticut and its tributaries formed at times when the process of gradual downcutting by the river was temporarily halted because of a bedrock obstruction in the stream channel. In this eventuality, that part of the river above the obstruction com- mences to meander from side to side, creating a flat floodplain at river level. If the river finally cuts its way around the downstream obstruction, its bed is abruptly lowered, and the recently-cut plain becomes a terrace perched above the river or stream.
Another conceivable explanation of terracing is related to the phenomenon of glacial rebound. The earth's crust is considerably weaker than we generally imagine, and it was strongly depressed, perhaps below sea level, by the Pleistocene ice cap. When the glacier retreated from New England, the crust eventually re-
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The Town's Prehistory
bounded to something close to its former elevation. A good indi- cation of post-glacial tilting in the Connecticut Valley is recorded by the deltas formed close to the shoreline of ancient Lake Hitch- cock. At one time these must have all been at the same level, yet today they decline from an elevation of 657 feet at Etna to ap- proximately 100 feet near Middletown, Connecticut. The average rate of southward post-glacial crustal tilt throughout the valley is, thus, approximately four feet per mile. If the rebound which has caused this tilting is intermittent, it may account for some of the terracing. During periods of no uplift, the river may establish a gentle drainage gradient, and a flat floodplain. If the crust sud- denly rises, the river must downcut rapidly to reestablish a smooth gradient; in this process the previous floodplain is abandoned, and may be preserved as a terrace above the new and lower river level.
With the preceding discussion of terracing, we have now fol- lowed the thread of history 450 million years into the present. To round off the picture, a brief survey of the mineral resources created during this long time span is, perhaps, appropriate. One might wish that he could write more glowingly about this facet of the town's development, but the facts are hard to improve. To Chase, writing his 1891 History of Dartmouth College and Han- over, N. H., the record of mineral productivity seemed so dismal as to prompt the comment that the town's mineral wealth, "what- ever it is, so far as is known, lies above ground."
History, unfortunately, does much to buttress this gloomy as- sessment. Even so common and necessary an agricultural com- modity as limestone does not occur within the town limits, and the early settlers of Hanover were obliged to obtain their supplies from quarries in the hills east of Plainfield, twelve miles to the south. According to a note left by the late Professor J. W. Gold- thwait, Slade Brook in the northwestern portion of Hanover is misnamed, and should be called Slate Brook because of a 1785 deed which reserves two acres for the Freeman slate quarry, a venture fated for swift oblivion. Copper ore, similar to that which has been mined so successfully at South Strafford and Ely, Ver- mont, has been known for at least seventy-five years in areas a mile north and a mile west of Mt. Tug, but not in sufficient abundance or richness to tempt even the most optimistic pro- moter. About thirty-five years ago Mr. Harley Camp of Etna opened a small flagstone quarry in the black schists a mile and a
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Hanover Bicentennial Book
half east of the village, on the south side of the road crossing Hayes Hill toward Ruddsboro. Several yards of material were quarried and used in Etna and Hanover, but the demand at that time was not high, and the venture was allowed to lapse. Lord's 1928 ac- count of the history of Hanover cites brickyards in three localities in the early town. There is, however, no mention of a kiln and it seems likely that the Hanover clays were never exploited. Accord- ing to Mr. Harley Camp, gold was found seventy-five years ago on the ridge behind the home of W. H. Hart in Etna village. The find, evidently, was a curiosity rather than a mineral deposit, and has long since been forgotten. Kyanite, an aluminum silicate with excellent refractory properties, occurs at Hayes Hill in Etna. Despite a 1941 publication by Dr. H. M. Bannerman describing the deposit, it still awaits drilling and possible development.
Of the mineral commodities significant in the town's economy, gravel and granite are the only ones which have had any extensive use or value. Mascoma granite from the Tilton quarry (two miles south of Goss Neighborhood and a mile east of Moose Mountain) was used, until seventy-five years ago, for the foundations of many of the homes in Etna. Lebanon granite has been quarried from many places in the area east of Hanover during the first 125 years of the town's history. The locations of the old workings and the building purposes for which the granite was quarried are set forth in some detail in the second volume of Hitchcock's Geology of New Hampshire (1877) and are therefore not repeated here. How- ever, the only use made of the granite within recent times has been for crushed rock. The Sullivan quarry at the east edge of Chase field was the source of the aggregate used in the concrete of the Alumni Gymnasium, built in 1907-1908. It also, for a while, functioned as a source of road metal, but the pit has now been closed for forty years. Bedrock quarrying within the town was last carried on about thirty years ago, when the New Hampshire High- way Department opened a working for crushed stone road metal in the green hornblende schists cropping out along the east side of Lyme Road, near the mouth of Camp Brook. This venture like- wise suffered an early demise.
The sand and gravel pits in the esker, at the Record and Cum- mings pits two and a half miles north of town, and at the Edgerton pit on Mink Brook are undoubtedly Hanover's most valuable nat- ural resource. If one adds to their output the value of the produc- tion of sand and gravel from the Sand Hill delta (the pits are now
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The Town's Prehistory
covered by Storrs Road and its houses) and of the Cutting Corner delta (at Etna) our debt to the Pleistocene glaciers is obvious.
One valuable resource which is neither mineable nor exhausti- ble, nor doomed for discard by the march of progress, is the rolling and picturesque countryside we are fortunate enough to inhabit. For this prized possession the town is indebted to the slow march of 450 million years of time.
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3 The River
by William Randall Waterman
W ITH the completion of the great power dam at Wilder late in 1950 the Connecticut River at Hanover acquired the character of an extensive, if narrow, lake. Upon this well-controlled and attractive body of water Dartmouth crews now practice and race, canoes glide quietly about, and outboard motors whine noisily. Occasionally a water skier displays his skill and a fisherman tries his luck. Of commercial activity there is none.
But if the river at Hanover has become something of an aquatic playground, such was far from being true in the early history of the town. For the first settlers the river offered a means of trans- portation to their new homes. The second family to settle in the town, Jonathan Lord with his wife and child, came up the river in a pine canoe in the spring of 1766. Others, no doubt, brought their families and simple household goods to Hanover in similar manner or in winter over the river ice. It was on the river, too, that the early settlers journeyed to the grist mill at Charlestown (Old Number Four), for Hanover's first mill on Mink Brook, in what is now Etna, was not built until 1769.
For upwards of forty years the river provided our forefathers with almost the only means of freighting their goods to and from the outside world. Well before the Revolution the transportation needs of Hanover and the upper valley of the Connecticut were being met by enterprising flatboatmen. In 1773 Benjamin Wright and Son were engaged in such a business, bringing goods up the river for the College. These early flatboats plied between the falls. Around the falls the goods were transhipped by oxcarts or horse wagons, to the profit of the neighboring farmers. Of these early flatboats little is known, but in the golden age of flatboating on the Connecticut they were, above Bellows Falls, some sixty feet in length and ten feet wide with the floor rising gently at either end. For use in favorable winds they carried a mast amidship with a large square sail. Downstream the boat moved with the current, steered by a great oar at the stern. Upstream the main dependence was on poling. For this purpose there were walkways on either side
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The River
of the boat. The polemen planted their long iron-tipped white ash poles firmly in the river bed, rested the upper end against their shoulders, and walked from bow to stern. This method of progress, about a mile an hour, was known as a "white ash breeze." It was laborious work, producing large shoulder calluses which were toughened by liberal applications of rum. Between Wells River and Hartford, Connecticut, the round trip took about thirty days, the customary freight charges being $20 per ton upstream and $10 downstream. From Hanover the time and charges were probably somewhat less.
Such were the transportation facilities that served Hanover un- til well into the nineteenth century. Up the river came both neces- sities and luxuries-"A General Assortment of English and West India Goods." Downstream in payment our ancestors sent such country produce as potash and pearlash, ginseng, butter, cheese, beeswax, grain, furs and pork, as well as shingles and lumber in the form of logs. For the convenience of the residents and mer- chants of Hanover and Norwich there were flatboat landings on either side of the river where the bridge now stands.
The growth of population and of trade following the Revolu- tion brought an increasing demand in the upper valley of the Connecticut for better transportation facilities. The answer ap- peared to lie in improving the navigation of the river. The chief obstacles to such improvement were the falls, of which there were six between Hanover and Hartford, Connecticut. In the valleys of the Potomac, the Mohawk and the Schuylkill about the same time, the solution to the problem of effectively "harnessing the rivers" was found to be in "locking the falls," that is, in circumventing the falls by a system of locks and canals. With such a project in mind on the Connecticut, the legislatures of New Hampshire and Vermont in 1792 incorporated a "Company for Rendering Con- necticut River Navigable by Bellows Falls." Similar companies were soon organized to lock the remaining falls and by 1810 the river was opened to through flatboat traffic from Wells River to Hartford.
The interest of Hanover in these efforts to improve the naviga- tion of the river lay in the White River Falls. These were about a mile and a half below the Hanover landing and just over the line in Lebanon near what is now Wilder, Vermont. Here the river fell thirty-seven feet in less than a mile, passing over three rock bars, the great fall being at the middle bar. It was at these falls that
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Hanover Bicentennial Book
Major Rogers and a remnant of his Rangers, returning from their raid on the village of the St. Francis Indians in the fall of 1759, wrecked their raft and almost met disaster as they "very narrowly escaped being carried over them by the current." The falls, in- deed, had long been noted for their violence and the necessity of a long carry.
In June 1792 the New Hampshire Legislature incorporated the White River Falls Bridge Company with authority to lock the falls, cut canals, and build a toll bridge within the limits of a grant extending from the mouth of Mink Brook in Hanover to the eddy below the lower bar in Lebanon. The incorporators were Aaron Hutchinson, a well-to-do lawyer and Justice of the Peace of Leba- non, General Ebenezer Brewster, one-time steward of the College and Hanover innkeeper, and Major Rufus Graves, a Dartmouth graduate and Hanover merchant. As it turned out, the White River Falls Bridge Company soon lost interest in the falls, con- centrating its attention on the toll bridge.
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