USA > New Hampshire > Atlas of the state of New Hampshire : including statistics and descriptions of its topography, geology, river systems, climatology, railroads, educational institutions, agricultural and botanical productions, mechanical and manufacturing interests, etc. > Part 3
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There are seventeen areas of this porphy- ritic rock in New-Hampshire. A very im- portant one is that which starts on the south side of Mt. Carrigain, passes to Waterville beneath the Labrador, re-appears at the sur- face, courses southerly in a continnous line of exposures to Meredithi, then comes back to Squam Lake, and then hends back again, and continues to Alton. To the west there aro several ranges. The principal one terminates in the corners of Bethlehem, Littleton and Dalton, re-appearing in Franconia, and con- tinuing interruptedly to Swansey, composing Mt. Kinsman, and the foot hills of Moosil- auke, Mts. Cardigan, Sunapee, Lovewell, etc. The smaller areas need not he specified in detail.
The most important features of this forma- tion are, 1. Its situation along the central part of the state, forming the "back hone" as it were, of New England. Being the oldest rock formed, it must have been dry land for a considerahlo period while the rest of New England, save the continuation of this rock southerly into Connecticut and its repetition in eastern Maine, was suhmerged. 2. The formations which succeeded were deposited simultaneously upou both flanks of this an- cient ridge. 3. "The ridge branches southerly, so that there must have been a gulf in ancient times in the hydrographic basin of the Mer- rimack River. 4. This ancient dry land un- dlerlies tho White Mountains, and probably did not extend farther north than Stratford though not now seen beyond Dalton and Whitefield. 5. As a similar rock is de- scrihed as occurring in Canada, this is be- lieved to be of the same age, or the Lauren- tian, the oldest formation in the world, known to man.
THE ATLANTIC SYSTEM.
Our reseurches in New- Hampshire lead us to revive an ancient designation for the crys- talline rocks along the Atlantic sea board in
distinction from the Laurentian or Adiron- dack group. The rocks of this system ex- tend continuously from Maine to Alabama, though nearly concealed by the superficial formations between New-York and Phila- delphia. Our theory in regard to their age is that they are posterior in time to the Lau- rentian, but anterior to the Cambrian and later formations. There is a difference in their mineral character, and certain general consid- eratious lead to the belief, that the eastern bor- der of the Continent was built up after that which has for the past fifteen years heen dis- tinctively known as the Laurentian. I can elassify them as follows in New-Hampshire. It remains to be proved by investigation in other states, whether any similar classifica- tion can be followed elsewhere. I cannot confidently give the formations in their proper order in time, without further study. 1. Bethlehem group. 2. Manchester or Lake Winnipiseogce range. 3. Montalban or White Mountain series. 4. Franconia breccia.
BETHLEHEM GNEISS .- There is an inter- esting talcose gueiss largely developed in Bethlehem and adjoining towns, which seems to constitute a formation entirely distinct from everything else. The orthoclase is abundant, usually pink or flesh colored, and mica is sparsely disseminated. It is granitic, also, occurring massive and without very dis- tinct lines of stratification. In our earlier researches it was called granite. The addi- tional feature which readily marks off this area from others, is the east and west strike common to the strata in Bethlehem. The area seeins to cut across the line of tho Coos and Ifuronian groups, as it it helonged to an older formation. The strike is more north- easterly in Whitefield. Other areas of this gneiss appear further south, as in Haverhill, where it cuts across the newer groups just as in Bethlehem, also in Lyme, Hanover, Leh- anon and elsewhere. Further researches will increase the area of this formation upon the map.
The greater age of the porphyritic gneiss may be seen in a section, from Bald Moun- tain in Franconia to the northwest corner of Bethlehem, where it is seen to form a syneli- nal axis or basis, in which the talcose rock re- poses, but with the strata apparently monocli- nal, in consequence of the enormous pressure to which the rocks have been subjected.
MANCHESTER OR LAKE RANGE .- This term may apply to a band of gneiss extending through Manchester from Mason to Deerfield. It is characterized by predominating in feld- spar, while the strata are often obscured, being nearly converted into granite. A similar range is found in Berlin.
To the northwest of the Manchester range is a band of commou gneiss, baving in it two interesting bands of quartz. The latter may be repetitions of the same bed. They have been traced, one from Temple and the otber from Mason to Allenstown. A similar gneiss, carrying tho same quartz, extends from Rich- mond to Franconia in the western part of the state. The most characteristic rock of this age, underlies Lake Winnipiseogee.
MONTALBAN OR THE WHITE MOUNTAIN SE- RIES. - The latter term was employed orig. inally to designate territorially, the central gnessic and granitic region of the state, ill- cluding what is now referred to the Lauren- tian and Atlantic divisions. The rock is often characterized by the presence of the mineral andalusite. Any one who has observed the rocks upon Mt. Washington along the trav. elled routes from Ammonoosuc to the Half- Way House on tho carriage road, may re- call crystalline bnnchies like small, woedy, weather-worn chips scattered through the ledges. Tbis mineral is called andalusite, and occurs abundantly in the White Mountains, though not universally. The rock contain- ing īt forms the main mass of the Mt. Washington range from Gorham to Hart's Location, ending with Mt. Webster. It ex- tends easterly to the Maine line hetween Suc- cess and Wakefield, and perhaps farther southi. Two interesting but isolated areas of it occur in Odell and Essex County Vermont On the west it appears along the valley of Pemigewasset and is extensively developed in the central and southern portions of the state.
In some regions the andalusite is very abundant, as in Weare and Francestown. A valuablo bed of soap-stone is contained in this variety of rock. It has been detected in Warner, Weare, Francestown, Richmond, and very likely in Keene. One of these beds is especially noteworthy on account of its use in the arts.
The Francestown Soapstone Co. with a enpital of $300,000 and large mills for sawing nt Nusbua, commenced to quarry their rock in May 1860. The bed was discovered by Mr. Ful- ler in 1800, when his Imrrow struck a soft rock. It was wrought extensively by Mr. Fuller and his son after him, for many years, and probably 2,000 tons of stone, in all, were sold by them. In 1866, 1,500, und in 1867, 2,020 tons were sold. Even the dust and refuse fragments are preserved and sold for packing. The opening is 80 feet long. 40 wide, and 80 deep, being a little wider at the bottom, On the surface the bed has been traced for 400 ft. 3,700 soap-stone stoves were made by the company in 1867.
Recent discoveries establish the relations of the White Mountain series to the adjoin- ing groups. Its upper limit is defined in the valley of Dry River, where it is unconform- ably overlaid hy Ossipyte, and lower down by the common granite, both of the Labrador series. General considerations, derived from studying its topographical relations to the porphyritie series, lead us to bolieve that it overlies the latter, and is therefore to be re- garded as above the Laurentian.
This conclusion differs from that put forth by Dr. T. Sterry Hunt in 1870, who includes our Coos group with it, and regards the whole as of pre-Cambrian age. Our later researches tend to show that the White Mountain or an- dalusite gneiss, is separated from the anda- Iusite slates of the Coos group by the whole of the Labrador system.
The New Hampshire granites, which are best known as building materials, belong to this formation. They are quarried in Con- cord, Fitzwilliam, Milford, Farmington, Hook- sett, Pelbam, Salem, Marlboro, Troy, Sunapee and elsewhere. The familiar name of "Gran- ite State" is very appropriate, as our re- sources in granite are rich, unlimited and
-
GEOLOGY.
wide spread. It is probably found in greater or smaller amount in every town underlaid by the White Mountain series. Besides these there are other extensive granites of the Labrador series, and limited patches of indigenous and eruptive masses in the Mer- rimack and Coos groups.
These granites are commonly fine grained and nearly white in color. Most of these quarries are easily accessible by railways. Three of the Concord companies, the "Gran- ite Railway," "Concord Granite," and " Don- agan and Davis," sell 8225,000 worth annu- ally, or about 7,000 tons. The Custom House nt Portland, Me., City Ilall and Advertiser building in Boston, and Booth's Theatre in New York, were built of Concord Granite. The largest block ever sent out of the state weighed 22 tons and 580 pounds. Accord- ing to the Census of 1860 there were four granite establishments or companies. $7,200 was the capital invested ; the raw material cost $1,825; thirty-eight hands were em- ployed; the cost of lahor was $15,312 and the value of the material manufactured $23,540.
Some of the coarse granite veins contain large plates of mica, which are extensively quarried. Some plates have been taken out measuring a yard square. The Ruggles Mica Co., of Grafton, marketed 75 boxes of 350 lbs. each of mica in 1869, worth from $2.15 to $2.50 per lb. They employed twelve men for seven months of the year. Mica is also quarried in the south part of Grafton, Alexandria and Acworth, and is found in Springfield.
The valley of the Saco River in the White Mountain Notch has been excavated out of granite by atmospheric erosion. Mt. Willey on the west and Mt. Webster on the east are composed of flinty rocks, both less liable to decomposition than the granite. As they form an anticlinal, though with an average dip of 75°.80° on both sides, the granite is wedge shaped and consequently the disinte- gration has left very steep walls. This is like notches in granite in other regions, as on Willoughby Lake in Vermont, and in the famous Yosemite valleys of California. The formation of the Noteh valley by simple de- nudation suggests the same reason for the formation of other valleys of similar shape, all over the country.
Along the edge of the schist and granite of Mt. Webster and further east thore aro enormous veins of granite, six, eight and ten rods wide, cutting into the schist for scores and hundreds of rods. This condition of things argues a large degree of plasticity in the granite when formed. A true eruptive granite, almost a diorito, occupies a consider- able area on the flank of Mt. Webster, below the Crawford House. Most of tho granite in the Aminonoosuc valley has the foldspar oc- surring in distinct crystals, porphyritic, not over half an inch in length.
LABRADOR SYSTEM .- At first we could refer to this system only those strata which were composed largely of the mineral labradorite, a lime-feldspar. But an examination of the
ledges shows a natural system of rocks, formed in one great period, which includes seven or eight members, most of them differing from the typical rock. They are, 1. Common or Conway granite. 2. Albany or spotted gran- ite. 3. Chocorua granite. 4. Ossipyte. 5. Dark compact Inhradorite. 6. Dark compact orthoclase. 7. Red compact orthoclase. 8. Reddish orthoclase. 9. Syenites. We will first describe the rocks and their distribu- tion, and afterwards give the reason for sup- posing them to constitute a single system.
CONWAY GRANITE .- The typo of this rock appears at the Basin, Pool and Flmine in Franconia, very often in Conway and at Goodrich's Falls in Jackson. The constitu- ents are rather coarse, never more than an inch, and usually one-fourth o. an inch long. The orthoclase is commonly flesh-colored and tho most abundant ingredient. The quartz is smoky, translucent, and often roughly crys- talized. The mica is bluck, and the least abundant of the three minerals.
The principal area of this rock is oval in shape, extending from Franconia to Chatham east and west, and from Carrol to Sandwich north and south. It seems to ho continuous over this whole area, the intorruption of con- tinuity upon the map arising from the pres- ence of overlying masses. It may be tho same with the material underlying the Porcy Peaks in Stratford. This granite is about six hundred feet thick in Franconia, and per- haps double this amount in the " Notch."
ALBANY GRANITE,-Whenever the com- mon granite does not reach the crest of a hill in the White Mountain area, it is capped by another variety of trachytic or semi-porphy- ritic aspect. The feldspar is ortboclase, and it is scattered through tho mass in rounded crystals imhedded in a granitic paste with scarcely any quartz. It often contains a small per cent. of manganese. The moun- tains made by it are the Twins, Haystack, Mt. Liberty, Mt. Osceola, and tbo Ossipee mountains south of the usual White Moun- tain area. The Chocorua granite is best do- veloped upon Mt. Chocorua in Albany. It is of a greenish color, and soems to pass into labradorite.
THE LABRADOR FELDSPARS .- None of theso were discovered till 1871. Their importance leads us to descrihe fully the locality in Wa- terville, where they were first discovered. It is upon " Norway Brook," the head of Mad river, the site of the notable slide or freshet of 1869. Many ledges that would otherwise have been concealed on account of tho easily decomposing character of the rock, were ex- posed to view by tbis rush of waters.
The first rock seen is a gneiss with nodular orthoclase, dipping by compass about 80° S, 70° W. The strata are indicated by folia of a dark hypersthenic minernl, often forming bunches or nodules. Jointed planes dipping about 25° westerly might be mistaken for strata. A few rods higher up the stream, the first ledge of the labradorite rock appears. Its junction with tho gneiss is concealed by drift. For about a mile the ledges are most-
ly composod of this rock, a compound of lab. radorite and chrysolite, some exposures appearing for sixty or soventy feet. Mr. E. S. Dana of New Ilnven, Ct., has npplicil to this compound the name of Ossipyte, after the name of the tribo of Indians (the Ossipees) formerly inhabiting this region. It is a per- plexing matter to determine the lines of strat- ification, as the outerops nre divided by two prominent sets of jointed planes, either of which might be called layers of deposition, the rock being essentially homogeneous. Ono set dip nbont 20° northerly, and are the most numerous. The other dips ahout 75° W. 10' S. Mr. Dana analyzed the two constitu- ents of this Ossipyto with the following re- sults, it being composed of the two minerals, labradorite and chrysolite.
LAURADORITE.
II.
111.
Menn.
SiO2
51.04
51,02
....
51.03
A1203 (TiO2) 26.34
26,07
....
26.220
Fc203
4.79
6.13
....
14.16
CaO
14.09
11.23
....
3.44
NaO
....
KO
..
...
10 1,37
Tbe large percentage of iron (determined volumotrically) had not been expected, as the eye had failed to detect any impurities in the fragments selected for analysis.' Some very thin pieces were afterwards examined under the microscope; and by this means it was found that even the clearest pieces con- tained vory minute grains of an iron ore, from ono fiftieth to ono two hundredtb of an inch in diameter, which were strongly ut- tractublo by the magnet. Microscopic dark specks less than one ten thousandth of nn inch in sizo were also observed, and at first referred to tho same canse ; but, ou magnify- ing them 800 diameters, it was concluded that they were air-cavities in tho structure of the feldspar, and not any foreign matter. The peculiar, dark, smoky color of the rock is doubtless to bo explained by tho presence of theso particles of iron oro.
This magnetic iron ore, a sufficient amount for the test having been picked out by the magnot, gave a decided reaction for titanic acid.
2. CHRYSOLITE,
Menn.
SiO2
38.82
38.88
38.80
Al2O3
tr.
Ir.
tr
Fed
28,00
28.15
28.07
MuO
1.12
1.36
1.24
MTO
30.88
30,36
30.02
CLO
1.26
1,60
1.13
100,08
100.36
100.21
The oxygen ratio of the basos and silica afforded is nearly 1 :1, and of the iron und magnesia about 1:2; whence tho formula (} Fe0-1-1MgO),SO,. This is then a chrysolite, containing an unusually large per centage of iron (here a constituent of tho mineral, and not owing to the presence of impurities). The amount of iron is not strange, consider- ing the fact that tho rock contains, diffused throughout it, so much freo iron ore.
This chrysolite has the same ratio deduced for hyalosiderite, but still differs widely in
,58
4.96
12
GEOLOGY.
fusibility and other characters. It is, in fact, a true cbrysolite in all respects, while hyalos- iderite is a doubtful compound, probably ow- ing its fusibility in part to tbe potash pres- ent. B. B. tbe chrysolite is nearly infusible.
The following is Mr. Dana's analysis of anotber spceimen of labradorite :
This feldspar has a grayish-white color, is destitute of iridescenee, and only careful searching reveals any striations. Two anal- yses afforded,-
I.
11.
111.
Mean.
SiO2
52.15
52.38
....
52.25
Al2O3
27.63
27.39
....
27.51
Fr203
1.09
1.07
....
1.08
MTO
.92
1.06
....
.
.99
CaO
13.10
13.45
....
13.22
NaO
. .
3.68
3.68
KO
....
.....
2.18
2.18
100.91
Botb analyses show that the labradorite of tbis region is remarkable for the large pro- portion of lime present.
Following up Norway brook tbe Ossi- pyte is abruptly succceded by a syenitic rock, fine grained, with little quartz and miea.
Tbe feldspar seems to be Labradorite. Tho line of junetion is irregular, averaging tbe course N. 20° E., while the dip of the planes of separation is about 85° westerly. Some of this feldspathie roek has been injee- ted into irregular cavities of the dark felsite. Still higher up, the stream has cut a deep notch into the mountain; and the rock is coarser grained, consisting of whitisb felds- par, which also is Labradorite according to recent-analyses, with hornblende, titanic iron, and a little epidote. This stream has worn its way along a ferruginous band, whieb may indicate tbe true position of the strata, dip- ping S. 76° E. and N. 55° E. The surface is almost entirely decomposed, though recently uncovered. Large nodules of essentially the same roek, hut very tough, abound; also geodie cavities with orthoclase, albite, quartz and rarely stilbite.
Abovo the ,noteb tbe rock is like that im- mediately succeeding the dark compound of labradorite and cbrysolite, with geodes, or feldspathiic veins. At the point where the slide proper commences, and tho valley turns at right angles, tho dip curves, and a new varioty of feldspathic rock is seen, which con- tinnes to the top of the mountain, the south- orn peak of Tri-pyramid. There is very little quartz, but two kinds of foldspar, one of tbem roddish, probably orthoclase. Mica is abund- ant and hornblende appears in rare speci- mens. The roek has a syentie aspect, con- taining geodes like those below, with actino- ite, amethyst, and other minerals.
Other localities aro tho sminmit of the Mt. Lafayette ridge, tops of tho Twin Mountains, Loou Pd. Mt., north of the Tripyramid, north of Mt. Tom near the Crawford House, valleys of Dry River and Rocky Branch, Sablo Mt., Jackson, Deer River valley near Mt. Choco- rua, the Pilot Knob and Starr King mass of mountains between Randolph and the G. T. R. in Stark.
UPPER COMPACT FELDSPAR .- The dark va- riety is well shown upon Mt. Lyon in North-
umberland. The red occurs plentifully as boulders in Waterville, but ledges on Deer River in Albany, and the sontb spur of the Twin mountains. The lighter varieties make up much of Mt. Carrigain, Little River mts. and peaks south of the G. T. R. They all seem to be arranged in horizontal masses.
SYENITES,-One mass whose feldspars are orthoelase, labradorite and andesite has been mentioned. Hornblende is not so commion as miea in it. Rocks of allied character occur upon Red Hill in Moultonboro and Sandwich, Mt. Gunstock and Belknap in Gilford, Mt. Monadnock of Vermont, near Colebrook, and elsewhere. These are refered to a period connected with the Labrador because tbe Tri- pyramid mass, though injected across ossi- pyte, contains tbe characteristic mineral. It is likely that the " Exeter Syenites " of our second report may provo to be of the same age,as there is a general minoralogical resem- blance between them all. These have been described as existing in Seabrook, at the end of the Quiney granite range of Massachusetts, in a range following the B. & M. R. R. from Dover to Kingston. For the present they may be considered as having been erupted at the close of the Labrador age,in New-Hamp- shire.
HURONIAN .- Recent developments lead us to refer the formations litlierto called " Que- hec group " in New-Hampshire, to the Hu- ronian system, which seems to be older than the Coos group and newer tbau tbe Labrador. Thero are three areas of it in the state. Tbe first extends about fifteen miles northerly from Bellows Falls. It may possibly join the next area, which is known to extend from the north edge of Charlestown along Connee- ticut river to Northumberland and Guildhall, Vt. Tbo third commences in Columbia and occupies most of the forest country about
the rock in Lisbon. Tbis led to the organi- zation of a mining company. In 1866 a bet- ter vein was found in Lyman, in the clay slate, and an association known as the Dodge Gold Mining Company formed to work it. Tbe two companies erected each a inill of ten · stamps, and before June 1, 1869, had sold not less than $16,000 worth of gold. The vein is whitisb quartz, often glassy, char- acterized by masses of pyrites, ankerite, gal- ena and slate scattered through it. Spangles of gold are common in the gangue. An exam- ination of the rock and imbedded minerals showed that there was an average of $18.90 of gold to the ton, and that most of it was eon- tained in the clear quartz, tho accompanying minerals being nearly destitute of it. The mineral character of this vein agrees with that of the auriferous sheets in Vermont and Canada. The gold is very nearly pure, con- taining only half of one per cent. of silver.
The shaft at tbe Dodge mine was sunk sev- enteen feet in 1867, and the rock taken ont yielded $6.25 per ton in the mill. After that the whole vein was quarried to the same depth for several rods, and yielded from 83 to $4 per ton. Next the work was renewed npon the shaft itself, and to the depth of seventy feet, including two drifts of sixty feet each, the average yield has been $7 per ton in the mill. In 1870 rock was taken out at a still greater depth, which yielded less than $2.00 to the ton. In 1873, under the guidance of Dr. J. H. Rae, new excavations brought up rock yielding from $ 18. to $ 25. per ton. The mines are now being worked more success- fully than ever before. Several other open- ings have been made in the neighborhood, both in the slate and sehist.
A section (fig. 3) in Lisbon and Lyman gives the following thickness for severai formations. At the southeast end of the sec-
N.W
20
13
13
18
Fig. 3 .- Section from Brepson's Lime Quarry to Smulth's Brook, Lyman.
1, Stulth's Brook : 2, Lisbon group : 3, Lyman group; 4, Aurlferons Con-
glomerato; 5, Quartz velns; 6, Anrifemhe quartz: 7, Clay alato; S, Lenticular quartx; D, Lisbon group; 10, Llabon villugo; 11, Swift Water serles; 12, Coos sintes; 13, Coos ochlats; 14, Milk Pond; 15, Staurolite guelsa and hornblende; 1G, Limestone.
Connecticut Lake, passing into Maine and Canada. A portion of the second area was described in the first annual report as the Ammonoosuc gold field. The existence of gold along Connecticut river was first inti- mated in the Geology of Vermont, hy the finding of specimens at Springfield, Vt., and the comparison of the rocks with those of the auriferous district further west .* In the Ge- ology of Maine it was also spoken of as one of the metals characterizing the scbist group extending from Bellows Falls to New Bruns. wick. The earliest discovery of gold in any part of it seems to have heen made by Mr. Hanshet in Plainfield, N. H., in 1854. About the same time Moses Durkee washod gold out of alluvium in Lebanon and Hanover.
The first discovery of gold in Lyman was made by Prof. Henry Wurtz of New York, in 1864. It was found in Galena. The next year J. Henry Allen and Charles Knapp, in. . dependently of each other, discovered gold in
"Final Report Geology of Vermont, 1661, pp. 683, 521. tSoientitio Survey of Maine, Second Annual Report p. 340.
tion, there are ordinary gneisses dipping about N. 20° W., and holding a band of azoic limestone, perhaps 100 feet thick, inclined 50°, which has heen extensively quarried hy Mr. Bronson. On the hillside toward the pond are friable gneisses, often very micace- ous and carrying simple crystals of stauro- lite, dipping 30°, N. 60° W. This is hord- ered by a band of hornblende schist dipping in the same direction ; 40° is the average for its whole width. The hornblende is an associ- ate of the gneiss formation rather than of what follows. The estimated thickness of this gneissic group is 2,500 feet. It is not clear to which of the gneissic divisions it be- longs, though allied to the White Mountain series in some respects.
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