Gazetteer of Grafton county, N. H. 1709-1886, Part 2

Author: Child, Hamilton, 1836- comp. cn
Publication date: 1886
Publisher: Syracuse, N. Y., Syracuse Journal Company, Printers
Number of Pages: 1266

USA > New Hampshire > Grafton County > Gazetteer of Grafton county, N. H. 1709-1886 > Part 2

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Bethlehem gneiss .- The typical localities of this rock are in this county. The best known is an area in Hanover and Lebanon, about ten miles long. "The center is a granite protogene, and is used for a bulding material. It is surrounded by a band of coarse mica chlorite schist, which we regard as the upper member of the series, and not to be confounded with an adjoining mica schist of the Coös group. In the Bethlehem area there is a pophyritic gneiss within the protogene and a more schistose variety without it, so that there are four members of the group at the north end of the county. Beds of limestone suitable for the manufacture of lime are found in this group, in Lis- bon, Haverhill and Lyme. Farther east there is a band of ordinary gneiss, stretching through the county from Grafton to Franconia. Its northern bor-

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GRAFTON COUNTY.

der occasionally rises to a considerable height, constituting Moose mountain, in Hanover, Smart's, in Dorchester, and the foundation of Mt. Cuba, in Orford. The southern part is a valley crowding close to the lower Laurentian, and in it is the magnetic iron veins of Lisbon, (Franconia) and Landaff. The maxi- mum thickness of this gneiss is 18,000 feet. The suggestion is natural that the protogene is the equivalent of the ordinary gneiss, the mica having been changed into chlorite or a hydrous mica. Another suggestion is that the ovoidal protogenic areas originated in an eruptive granite, operated upon by great pressure so as to induce the quadruple concentric structure described above. Some authors believe that the schistose structure is generally occas- ioned by pressure, and that the original rock has had no connection with de- posits of a sedimentary character.

Montalban .- The upper Laurentian is an imperfect gneiss, but shown just east of the county in the White Mountains, and attaining a thickness of 12,000 feet. It may be seen in the Pemigewasset valley. In the New Hampshire report another group of rocks was referred to the age, which is best developed between Plymouth and Grafton. It is a band of hard mica schist interpene- trated by fibers of the mineral fibrolite, and has been filled by large veins of coarse granite, whose mica is mined for use in the arts. These veins also hold large beryls, apatite, albite, tin ore, tourmaline, triplite and other minerals.

Huronian .- In the " Ammonoosuc mining district " this system is best de- veloped. The lowest member is thought to be identical with the belt of hornblende schist traceable along the Connecticut river from Lebanon to Orford. At Hanover the formation is not less than 1,000 feet thick, as it underlies Darmouth college. Handsome garnets checker the beds close by the old pine where the college classes sing their parting songs. At Lisbon the lower division is a green chloritic schist alternating with greenish quartzites, diabases and hydro-mica schist. In Lyman the upper members developed consisting mostly of grey argillitic quartzites. Upon Gardner mountain this member changes into the Cornish kellas and is filled with copper and iron pyrites, sufficiently for mining. Above all the others is a thin band of con- glomerate shown by analysis to contain a small amount of gold. The total thickness is about 12,000 feet.

Cambrian .- A clay slate about 3,000 feet thick overlies the Lyman group of the Huronian throughout the Ammonoosuc district, and again on the wes- tern flank of the Huronian, farther south, this is traversed by auriferous quartz veins. One of these has been mined in Lyman for a number of years. About $60,000 of the gold coin in circulation came from this mine. The best part of the vein averaged about $18.00 to the ton of rock. The rock has also been quarried for roofing slate in Littleton.

Coös Group .- In the Connecticut valley is a broad band of mica schist belong- ing to a still later series, apparently. It is characterized by the presence of the mineral staurolite. The basal member is a quartzite 1,000 feet thick, which by its unyielding nature causes mountains to project above , the general level.

GEOLOGICAL.

It adds to the altitude of Moose mountain in Hanover and Cuba mountain in Orford, and is the main mass of Piermont mountain. In Hanover and Lyme the quartzite is reported nearer the Connecticut. The Coös rocks between Lebanon and Orford are partially made up of chloritic schist, and a rare bed of limestone, suggesting the calciferous mica schist of adjacent counties. The most characteristic rock of the group is an argillaceous and micaceous schist filled with staurolite. The best localities of this mineral are in the towns of Lisbon, Enfield and Grantham, where cruciform crystals are quite common. It was shown early in the history of the state survey that the Coos group was newest of all the crystalline schists of New England, and that it may possibly belong to the Paleozoic age. Considerable heat must have been evolved in order explain the presence of the staurolite. This does not seem to have been derived from the proximity of igneous rocks, but to have been liberated by the elevation of the strata.

Niagara Group .- Greatly to the delight of geologists, a few fossils have been discovered in Littleton and Lisbon, belonging to the upper Silurian. They are the chain-coral, honey-comb coral and other related forms, Penta- merus Nysius, a bivalve brachiopod shell and crinoidal fragments. The rocks overlie all the crystalline schists of the neighborhood, and are readily distin- guished from the Coos strata. There is no ground for the opinion that these fossiliferous strata are interstratified with the crystalline, and thus for the hypothesis of the formation of the latter from Paleozoic sediments. Slates and limestones represent the group with the possible addition of sandstone and quartzites.

UNSTRATIFIED OR ERUPTIVE ROCKS.

Grafton county furnishes many fine illustrations of rocks that have once been melted, and most likely derived from the great internal caldron ever ready to belch forth an igneous fluid. The Basic division, represented by diabase, diorite and gabbro, is known only in dikes, which are the filling up of fissures by molten matter injected from below. The diabase is a black or dark grey, fine grained rock, quite heavy, and a microscope is needed to discover that the constituent minerals are augite, labradorite and magnetic or titanic iron. Diorite differs from diabase only by having hornblende in the place of augite. The gabbro is more like granite of coarser grain, but has the same constituents as diabase, the augite being foliated.

A noted locality of the diabase is at the Flume in Lincoln (Franconia). A dike of this material rather more than a yard wide occupies the middle of the chasm. When melted it not only filled the chasm but also induced jointed planes of division in the granite adjacent. The water wore away the dike first, and then water flowing into the cracks froze and thus gradually pried off fragments which were washed away by the stream. A continuation of this process for ages finally produced the Flume. In the ice age a large boulder

GRAFTON COUNTY.

was brought from near the Profile House and left so that it rolled into the flume and remained till 1883, as a bridge over the chasm, and a terror to timid people walking beneath. In this last named year slides rolled down tlie sides of Mts. Flume and Liberty, the most gigantic masses of debris known to move down mountain slopes within the memory of man in New Hamp- shire, and enough pushed its way through the flume to remove this boulder and bury it deep in the rubbish a thousand feet below. The stone which is carefully fenced in and labelled as the original one is unfortunately about two feet shorter than the first named.

The most prolific locality of these basic dikes is at Livermore Falls, near Plymouth, at a railroad station. Five or six of them crop out on the high cliff upon the west side of the Pemigewasset river, and in the railroad cut. There are diabases, diorite, syenite, coarse granite, and olivine diabase.

At Waterville the gabbro is immensely developed, covering two or three square miles on the west and south flanks of Tripyrimid. It was unknown till revealed by the slides of 1869 and 1885.

Of the Acidic division porphyry is finely developed in the south part of the Twin mountains, of variegated and bright red colors, suitable for ornamen- tal purposes. It is not utilized at present. The granites with the porphyry occupy an oval area of about 300 square miles in the White mountain region, and are believed to have been of eruptive origin. We have made careful studies of this region and think but to give some of the results in respect to the origin of granite, as the subject has not been well understood in the past even by those familiar with geology.

The origin of granite .- The more this rock is studied the clearer does it seem to have had an eruptive origin. Many authors have supposed it to repre- sent an altered stratified rock, partially fused through thermal action. Thanks to the use of the miscroscope the intimate composition of crystals may 110w be thoroughly studied and their origin made known. One of the best known localities for exhibiting the phenomena of eruption is the range overlooking Fabyans and the White Mountain Notch, seen most advantageously in Mt. Willard.

This mountain is nearly 3,000 feet above the sea, and about 1,000 feet above the Notch at the Crawford House. Most of it is composed of a hard mica schist or gneiss belonging to the Montalban series, and it is the south end of the great range of mountains named after the President of the United States. This rock has been cut by dikes of eruptive granite. Two or three separate outbursts may be seen. The first and oldest is that termed Con- way granite, a coarse grained rock having black mica or biotite for its third constituent. It once filled the valley of the White Mountain Notch, and reaches westerly across to Franconia; north to the Twin Mountain House, and south to Waterville, covering 200 or 300 square miles. A second is termed Albany granite, both names being derived from the towns where they abound. This Albany rock gives the best signs of igneous fluidity, as it flowed

GEOLOGICAL.

upwards in a rent between Conway granite on one side and the compact andalusite mica schist in the other, elsewhere known as the Kearsage group. This mica schist has had its character changed by contact with the igneous vein, while the Conway granite was unaltered, having once been melted itself, and therefore incapable of further change by heat.

The Montalban rocks were terribly shattered before the protrusion of the Conway granite, and its fragment cemented by a third igneous paste called for convenience a breccia granite. This is finely shown where the railroad passes around the southeast angle of the mountains. The vein of perhaps 300 feet in width crosses the valley at the Dismal Pool and runs transversely up the side of Mt. Webster. The Conway granite joins this breccia on Mt. Willard, and the sharp line of junction may be followed the whole height of the cliff, showing that the two rocks were erupted at different periods.

The Albany granite has filled a fissure between the Conway granite on the east and the Kearsage mica schist upon the west. Near both walls the felds- par crystals are better formed than in the center, accompanied by dihexago- nal pyramids of quartz. In the middle the matrix is a grey fine-granular ag- gregate, having the color of a mixture of pepper and salt. The many crystals of feldspar render the rock spotted in appearance. Examined microscopically the fine-granular mass shows amorphous quartz with inclosed fluids, hornblende, biotite, magnetite, apatite, augite and fluorspar ; but the most marked char- acter is the uniform presence of square prisms of zircons. The changed ap- pearance next the walls, developing a porphyry, is due to the effect of contact of heated material with cold surfaces. Upon examining the mica schist fifty feet distant from contact with the granite, it is seen to consist of quartz, white mica or muscovite and chlorite with pencils of andalusite, with a very little biotite, iron minerals and tourmaline. At the distance of twenty-five feet the schists are less earthy and the biotite and tourmaline crystals have increased in quantity. At fifteen feet the chlorite has disappeared, and the rock is still a mica schist. Between this point and the contact the schist loses its structure and becomes a black hornstone, breaking into angular frag- ments. Still nearer the granite is a dark grey mass filled with reticulated black veins. This is scarcely noticeable at the top of the mountain but becomes wide and prominent below. Microscopically it is found to be a nearly pure mixture of tourmaline and quartz, and is termed tourmaline veinstone. The remaining zone is a breccia composed of fragments of various schists and quartz porphyry cemented by granitic material. There is, however, a systematic and progressive series of changes ; first, water has been removed ; second, boric acid and silica have been added; third, alkalies have been added directly upon the contact. These additions and changes are such as would come from igneous eruptions, and therefore the inference is authorized that the Albany granite was injected as a melted liquid like lava. The vein may be followed the whole length of the Rosebrook range adjoining the Con- way granite, as well as over the entire White Mountain region of eruptive rocks.

GRAFTON COUNTY.

If thoroughly igneous at Mt. Willard it must have had a similar origin else- where.

Granitic Cones .- Another form of the granite or syenite is that of a cone. Examples are Catamount hill in Haverhill, and that interesting crescent line of isolated peaks, Mts. Nancy, Anderson, Lowell, Cardigan, Hancock and Hitchcock. When adjacent to schistose rocks the heat has altered the sedi- ment somewhat as on Mt. Willard. Observation shows that the granite came up through a vent directly under the apex of the cone, that when soft the pasty material oozed from the opening and gradually accumulated till the whole mountain was built up. Wherever the slaty flow can be examined it is found to be altered by the impact of the hot granite, This is a great im- provement over the old idea that granite has formed only at a great depth, say beneath 40,000 feet of sediments, for in that case it is necessary to be- lieve in the subsequent removal of this immense mass by denudation. The present view regards the granite piles to have originated just as conical beds of lava accumulate at the present day.

BEGINNING OF DRY LAND.

In another place (Vol I., Geology of New Hampshire) I have given a series of maps showing how the dry land of the State has been gradually reclaimed from the primitive ocean, beginning with the areas of porphyritic gneiss. I have latterly gone further and claimed that these same areas, with others like them, constituted the nucleus of the North American continent. It would seem as if these projections, or islands, were of eruptive origin, very much like submarine volcanoes, the first that appeared after a crust had formed around the earth. Later ejections increased their dimensions and sediment came down the slopes so as gradually to unite the cones. A continuation of the earth's contraction would tend to raise the earlier heaps of eruptive debris and thus to construct a continent. This view gives us the advantage of fix- ing upon the very beginning of terrestrial accumulation, instead of being forced to imagine a basin in which these earliest accumulations were de- posited as sediment. As this theory has been broached but recently, a few points may be cited in its favor, as follows :-

First :- Considering the igneous nature of the earth, volcanic energies would naturally continue their action as soon as there was a crust to be broken through, and immense molten floods would ooze through the fissures. We are now beginning to understand that the numerous granites, syenites and porphyries of our region were eruptive, and that the older the period, the more numerous the igneous rocks.

Second :- We have found ovoidal areas in Grafton county of both the old- est and later gneisses, while they are very numerous in other parts of the State. A careful study of some of them reveals a concentric structure, just such as- would arise from the accumulation of molten rock, rather than from sedimen-

GEOLOGICAL.

tary deposits. Doubtless this concentricity will be found in all these areas when minutely studied. A somewhat similar structure is apparent in large volca- noes like Vesuvius. Should that volcano cease to be active, rains would obliterate the craters and reduce the lava to a rounded dome, which, when cut into, would show concentric layers of differently constituted aggregations.

Third :- The difficulty in deciding whether our oldest group is granite or gneiss from an inspection of its crystalline particles, is just what may be expected upon our theory of its origin. Furthermore, all the special mineral peculiarities of true eruptive granite are to be noticed in our rock. Hence we would say that gneiss is derived from granite by pressure, rather than that granite is gneiss melted down.

Fourth :- The analogy of the origin of oceanic islands at the present day, suggest the igneous derivation of the Laurentian areas. Most of the high islands of the Pacific are composed of lava, built up from submarine volca- noes ; and the lower lands may have been the same originally, supplemented by the labor of coral animals. The size of a cluster of Pacific islands is cer- tainly not inferior to that required to equal our American grauite areas. The Hawaiian islands have a base of 100,000 square miles, which exceeds the di- mensions of New England.

THE AGE OF ICE.

Volumes would be required to present all the facts of interest respecting the cold period of geological time known as the Age of Ice. Our country was overspread by a glacial sheet shortly before the introduction of man, and its relics may be seen in the smoothing and the striation of the rocks and the universal dispersion of bowlders. Three stages of progress are demonstrable : First, the accumulation of a thick coating of ice which covered every square foot of land, not excepting the summit of Mount Washington. Where the sea washed the edge of the ice, characteristic deposits were left. Second, this ice-sheet melted rapidly, and enormous floods of water transported the coarse gravel now arranged in the celebrated horsebacks, eskers or kames, great plains of sand and clay, and river terraces. The time was brief, and corresponded very well to the violent and powerful action of spring freshets. Third, after the removal of the ice and the floods, the country must have been barren till vegetation revived, and the geological changes effected have been comparatively unimportant.

Two hundred courses of striæ for Grafton county are given in the State report. It would appear that the southeast and southerly courses are the most common, pointing to the elevated land between the St. Lawrence river and Hudson Bay as the origin of the glacier. Observations elsewhere indi- cate that the ice moved radially from those high lands, viz., northerly towards the Arctic regions; northeasterly over Labrador towards Greenland; south- easterly over Newfoundland, New Brunswick, and New England ; and espec- ially southwesterly towards Dakota and the Missouri river. The resistance

GRAFTON COUNTY.

from high land was least in that direction, and glacial markings extend nearly a thousand miles. Inasmuch as the White Mountains are more elevated than the Laurentian high lands, it is necessary to believe either that the country was much more elevated in the ice age than at pres- ent, or else that the ice itself accumulated thousands of feet in thickness, and in consequence of its great altitude, was enabled to flow over the moun- tains of New England. It would seem as if the St. Lawrence valley must have been filled up to the brim before any of the ice flowed over New Hamp- shire. If so, it is likely that in New England the cold age did not commence so early as in Canada and the Western United States.

The deposits left by the glacier are mainly examples of the ground moraine -a species of glacial deposit neglected by most Alpine observers. When the glacier had greatly diminished streams would have appeared in such of the river valleys as were well adapted to hold them and of which examples have been cited in my State reports. Terminal, lateral, and medial moraines may be found occasionally in such valleys. This moraine is commonly termed till, a term of Scotch origin. It is of two parts, the upper and lower. The Jatter is the most abundant and characteristic. It may be recognized by its great compactness, blue color, and the presence of stones that are scratched or worn and that have come from great distances. In Hanover one often finds red stones which have been transported more than seventy miles, from the neighborhood of Burlington, Vt. These bowlders are usually quadrangular or trapezoidal in outline, with the striae upon four sides parallel to the great- est length of the stone. The upper till is loose, brownish red, and carries rough unworn stones that have been transported a very little distance. It is supposed that the lower till derives its compactness from the weight of ice over it, while the upper till consists of the fragments embedded in or resting upon the ice at the time of melting. With this view the degree of oxidation of the iron corresponds. That which is blue represents the ferrous unstable condition, being the freshly pulverized rock scarcely exposed to oxidating in- fluences ; the brownish red earth has been wet in the presence of the atmos- phere, and thus easily converted into the hydrated ferric oxide.

The Connecticut valley affords a fine illustration of an esker or kame. This deposit is a straight ridge of gravel, with arched stratification, occupying the lowest line of the valley. It is not seen north of Lyme, and it crosses very shortly into Thetford and Norwich, where it has been cut through by the Pompanoosuc river. About two miles north of the Ledyard bridge in Han- over, it returns into New Hampshire, and then returns to Hartford, Vermont, in season to be cut through by the White river at the Railroad junction, and thence it may be followed to Windsor. The gaps in it uniformly show sand, gravel and water-worn cobblestones, in a very narrow belt, and at Hanover plain the ridge has been partially covered by the later fluviatile deposits. Its origin may be conceived by supposing the material filled a chasm in the ice deposited by the rapidly rising river. The ice bordering the chasm would

BOTANICAL.

have held the gravel in place till the amelioration of the climate removed the glacial sheet. Immediately succeeding the formation of the esker the water must have increased in volume enormously, being at least 175 feet higher than now at Hanover, and more than 200 feet higher at Woodsville, where the great tributaries of Wells and Ammonoosuc rivers greatly swelled the volume of the Connecticut. The immediate result of such a freshet was the filling of the bottom of the valley with a blanket of sand, gravel and clay. As the water diminished in volume, it cut through the flood-plain and carved out the ter- races which now adorn the flanks of the hills and furnish beautiful sites for villages and private residences.

BOTANICAL.

Because of having Dartmouth college within its limits as a scientific center, the flora of Grafton county has been more carefully studied than other parts of the State, and those interested in this subject should consult a catalogue of the " Flora and Fauna of Hanover and Vicinity," published by Prof. H. G. Jesup, in 1882. This catalogue contains most of the species occurring in the county, with hints at range and distribution. The catalogue which we place before the reader, for which we are indebted to William F. Flint, B. S., of Winchester, N. H., is only approximately correct, and necessarily without reference to distribution. For botanical discriptions the reader is refered to Gray's " Manual," or Wood's " Class-book of Botany," which are generally used in the higher schools. Our catalogue, we would say, also, includes the ferns, but not the mosses and lichens, as their discriptions are not easily acces- sible to the general public.

As altitude above the sea level is the prime factor governing plant distri- bution, the county is a region in which northern types are predominant in its flora. The portions where the Alleghenian types occur abundantly, as those plants which prevail in southern New England are called, are restricted to the immediate vicinity of the Connecticut and Pemigewasset rivers and their principal tributaries. An examination of the plants of this limited territory, however, reveals the fact that many of the plants which are common to the same river valleys southward, yet within the New Hampshire limits, have either totally, disappeared or been replaced by a more northern species. Thus the chestnut ( C'astanea vulgaris, var Americana) is no longer indigenous, having disappeared within the limits of Sullivan county. This is true also of the yellow barked, or black oak ( Quercus tinctoria), the barren or scrub oak, ( Q.ilicifolia), the black and the grey birches, (Betula lenta and B. alba, var, populifolia), the mountain laurel, (Kalmia latifolia), the Rhododendrons, two of the blue berries ( Vaccinum), and many others, both shrubs and herbaceous plants. Only one species of hickory persists, the bitter or swamp hickory (Carya amara), which is found very near the river, north to the mouth of the Ammonoosuc, while the hackberry, ( Celtis occidentalis), which find its eastern limit on the Connecticut, also appears near the same locality.

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Gazetteer of Grafton county, N. H. 1709-1886, Part 2

Author: Child, Hamilton, 1836- comp. cn Publication date: 1886 Publisher: Syracuse, N. Y., Syracuse Journal Company, Printers Number of Pages: 1266

Author: Child, Hamilton, 1836- comp. cn
Publication date: 1886
Publisher: Syracuse, N. Y., Syracuse Journal Company, Printers
Number of Pages: 1266