Scientific American Supplement, No. 363, December 16, 1882
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Various >> Scientific American Supplement, No. 363, December 16, 1882
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But the main result seems to be still this, that as we have seen in the
earth's atmosphere, so we see in the sun's, an enormous and progressive
increase of the energy toward the shorter wave-lengths. This conclusion,
which, I may be permitted to remark, I anticipated in a communication
published in the _Comptes Rendus_ of the Institute of France as long
since as 1875, is now fully confirmed, and I may mention that it is so
also by direct photometric methods, not here given.
If, then, we ask how the solar photosphere would appear to the eye,
could we see it without absorption, these figures appear to show
conclusively that it would be _blue_. Not to rely on any assumption,
however, we have, by various methods at Allegheny, reproduced this
color.
Thus (to indicate roughly the principle used), taking three Maxwell's
disks, a red, green, and blue, so as to reproduce white, we note the
three corresponding ordinates at the earth's surface spectrum, and,
comparing these with the same ordinates in the curve giving the energy
at the solar surface, we rearrange the disks, so as to give the
proportion of red, green, and blue which would be seen _there_, and
obtain by their revolution a tint which must approximately represent
that at the photosphere, and which is most similar to that of a blue
near Fraunhofer's "F."
The conclusion, then, is that, while all radiations emanate from the
solar surface, including red and infra-red, in greater degree than we
receive them, the blue end is so enormously greater in proportion that
the proper color of the sun, as seen at the photosphere is blue--not
only "bluish," but positively and distinctly blue; a statement which I
have not ventured to make from any conjecture, or on any less cause than
on the sole ground of long continued experiments, which, commenced some
seven years since, have within the past two years irresistibly tended to
the present conclusion.
The mass of observations on which it rests must be reserved for more
detailed publication elsewhere. At present, I can only thank the
association for the courtesy which has given me the much prized
opportunity of laying before them this indication of methods and
results.
* * * * *
THE MINERALOGICAL LOCALITIES IN AND AROUND NEW YORK CITY, AND THE
MINERALS OCCURRING THEREIN.
[Footnote: Continued from SUPPLEMENTS 244 and 246.]
By NELSON H. DABTON.
PART III.
Hoboken.--The locality represented here is where the same serpentine
that we met on Staten Island crops out, and is known as Castle Hill. It
is a prominent object in view when on the Hudson River, lying on Castle
Point just above the Stevens Institute and about a mile north of the
ferry from Barclay or Christopher Street, New York city. Upon it is the
Stevens estate, etc., which is ordinarily inaccessible, but below this
and along the river walk, commencing at Fifth Street and to Twelfth,
there is an almost uninterrupted outcrop from two to thirty feet in
thickness and plentifully interspersed with the veins of the minerals
of the locality, which are very similar to those of Staten Island; the
serpentine, however, presenting quite a different appearance, being of a
denser and more homogeneous structure and color, and not so brittle or
light colored as that of Staten Island, but of a pure green color. The
veins of minerals are about a half an inch to--in the case of druses
of magnesite, which penetrate the rock in all proportions and
directions--even six inches in thickness. They lie generally in a
perpendicular position, but are frequently bent and contorted in every
direction. They are the more abundant where the rock is soft, as veins,
but included minerals are more plentiful in the harder rock. There is
hardly any one point on the outcrop that may be said to be favored in
abundance, but the veins of the brucites, dolomite, and magnesites are
scattered at regular and short intervals, except perhaps the last, which
is most plentiful at the north end of the walk.
_Magnesite_.--This mineral, of which we obtained some fine specimens on
Staten Island, occurs extremely plentifully here, constituting five or
six per cent. of a large proportion of the rock, and in every imaginable
condition, from a smooth, even, dark colored mass apparently devoid of
crystalline form, to druses of very small but beautiful crystals, which
are obtained by selecting a vein with an opening say from a quarter to a
half-inch between it and one or, if possible, both points of its contact
with the inclosing rock, and cutting away the massive magnesite and rock
around it, when fine druses and masses or geodes may be generally found
and carefully cut out. The crystals are generally less than a quarter of
an inch long, and the selection of a cabinet specimen should be based
more upon their form of aggregation that the size of the crystals.
Nearly all the veins hold more or less of these masses through their
total extent, but many have been removed, and consequently a careful
search over the veins for the above indications, of which there are
still plenty undeveloped or but partly so, would well repay an hour
or more of cutting into, by the specimens obtained. Patience is an
excellent and very necessary virtue in searching for pockets of
minerals, and is even more necessary here among the multitudinous barren
veins. One hint I might add, which is of final importance, and the
ignorance of which has so far preserved this old locality from
exhaustion, is that every specimen of this kind in the serpentine, of
any great uniqueness, is to be found within five feet from the upper or
surface end of the vein, which in this locality is inaccessible in the
more favored parts without a ladder or similar arrangement upon which
one may work to reach them. Here the veins will be found to be very far
disintegrated and cavernous, thus possessing the requisite conditions of
occurrence (this is also true of Staten Island, but there more or less
inaccessible) for this mineral and similar ones that occur in geodes or
drused incrustations, while it is just _vice versa_ for those occurring
in closely packed veins, as brucite, soapstone, asbestos, etc., where
they occur in finer specimens, where they are the more compact, which is
deep underground. This is also partly true of the zeolites and granular
limestone species with included minerals. I do not think there is any
rule, at least I have not observed it in an extended mineralogical
experience; but if they favor any part, it is undoubtedly the top, as
in the granular limestone and granite; however, they generally fall
subordinate to the first principle, as they more frequently, in this
formation, with the exception of chromic iron, occur not in the
serpentine but in the veins therein contained; for instance, crystals
of dolomite are found deeper in the rock as they occur in the denser
soapstone, which becomes so at a more or less considerable depth, with
spinel, zircon, etc., of the granular limestone. They occur generally in
pockets within five feat from the surface, but they can hardly be called
included minerals, as they are rather, as their mention suggests,
pockets, and adjacent or in contact with the intruded granite or
metamorphosed rock joining the formation at this point. This is
seemingly at variance when we consider datholite, but when we do find it
in pockets a hundred and fifty feet below the surface, in the Weehawken
tunnel, it is not in the trap, but on the surface of what was a cleft
or empty vein, since filled up with chlorite extending from the surface
down, while natrolite, etc., by the trap having clefts of such variable
and often great depth, allowed the solution of the portion thus
contributed that infiltered from the surface easy access to the beds
in which they lie, the mode of access being since filled with densely
packed calcite, which was present in over-abundance. This is not
applicable to serpentine, as the clefts are never of any great depth,
and the five feet before mentioned are a proportionately great depth
from the surface. As I mentioned in commencing this paper (Part I),
every part of the success of a trip lies in knowing where to find the
minerals sought; and by close observation of these relations much more
direction may be obtained than by my trying to describe the exact point
in a locality where I have obtained them or seen them. There is much
more satisfaction in finding rich pockets independently of direction,
and by close observance of indications rather than chance, or by having
them pointed out; for the one that reads this, and goes ahead of you to
the spot, and either destroys the remainder by promiscuous cuttings, or
carries them off in bulk, as there are many who go to a locality, and
what they cannot carry off they destroy, give you a disappointment in
finding nothing; consequently, I have considered that this digression
from our subject in detail was pardonable, that one may be independent
of the stated parts of the locality, and not too confidently rely on
them, as I am sometimes disappointed myself in localities and pockets
that I discover in spare time by finding that some one has been there
between times, and carried off the remainder. The characteristics of
magnesite I have detailed under that head under Pavilion Hill, Staten
Island; but it may be well to repeat them briefly here. Form as above
described, from a white to darker dirty color. Specific gravity, 2.8-3;
hardness, about 3.5. Before the blowpipe it is infusible, _and not
reduced to quicklime_, which distinguishes it from dolomite, which it
frequently resembles in the latter's massive form, common here in veins.
It dissolves in acid readily with but little effervescence, which
little, however, distinguishes it from brucite, which it sometimes
resembles and which has a much lower-specific gravity when pure.
_Dolomite_.--This mineral has been very common in this locality.
It differs, perhaps, as I have before explained, from magnesite in
containing lime besides magnesia, and from calc spar by the _vice
versa_. Much of the magnesite in this serpentine contains more or less
lime, and is consequently in places almost pure dolomite, although
crystals are seldom to be found in this outcrop, it all occurring as
veins about a half-inch thick and resembling somewhat the gurhofite
of Staten Island, only that it is softer and less homogeneous in
appearance. Its color is slightly tinged green, and specimens of it are
not peculiarly unique, but perhaps worth removing. Its characteristics
are: first, its burning to quicklime before the blowpipe, distinguishing
it from pure magnesite; second, its slow effervescence in acids. Besides
these, its specific gravity is 2.8, hardness, 8.5; from calcspar it
cannot be distinguished except by chemical analysis, as the two species
blend almost completely with every intermediate stage of composition
into either calc spar, or, what occurs in this locality, aragonite,
similar in composition to it, or dolomite. The color of the last,
however, is generally darker, and it cleaves less readily into its
crystalline form, which is similar to calc spar, and of which it is
harder, 3.5 to 3 of calc spar.
_Aragonite_.--This mineral, identical in composition with calc spar, but
whose crystalline form is entirely different, occurs in this locality in
veins hardly recognizable from the magnesite or dolomite, and running
into dolomite. It is not abundant, and the veins are limited in extent;
the only distinguishment it has from the dolomite, practically, is its
fibrous structure, the fibers being brittle and very coarse. If examined
with a powerful glass, they will be seen to be made up of modified long
prisms. The specific gravity is over 2.9, hardness about 4, unless much
weathered, when it becomes apparently less. There are some small veins
at the north end of the walk, and in them excellent forms may be found
by cutting into the veins.
_Brucite_.--This mineral occurs here in fair abundance, it being one of
the principal localities for it in the United States, and where formerly
extremely unique specimens were to be obtained. It has been pretty well
exhausted, however, and the fine specimens are only to be obtained by
digging into the veins of it in the rock, which are quite abundant on
the south end of the walk, and, as I before noted, as deep as possible
from the top of the veins, as it is a closely packed mineral not
occurring in geodes, druses, etc. Two forms of it occur; the one,
nemalite, is in fibers of a white to brown color resembling asbestos,
but the fibers are brittle, and hardly as fine as a typical asbestos. It
is packed in masses resembling the brucite, from which it only differs
in breaking into fibers instead of plates, as I have explained in my
description of that species (see Part II). They are both readily soluble
in acids, with effervescence, and infusible but crumble to powder before
the blowpipe, or at least become brittle; when rubbed in mass with a
piece of iron, they phosphoresce with a yellow light; specific gravity,
2.4, hardness, 1.5 to 2. Its ready solubility in acids without
effervescence at once distinguishes it from any mineral that it may
resemble. The specimens of nemalite may be more readily obtained than
the brucite but fine specimens of both may be obtained after finding a
vein of it, by cutting away the rock, which is not hard to do, as it
is in layers and masses packed together, and which maybe wedged out in
large masses at a time with the cold chisel and hammer, perhaps at the
rate of three or four cubic feet an hour for the first hour, and in
rapidly decreasing rate as progress is made toward the unweathered rock
and untouched brucite, etc.
_Serpentine_.--Fair specimens of this may be obtained of a dark oil
green color, but not translucent or peculiarly perfect forms. The
variety known as marmolite, which splits into thin leaves, is plentiful
and often well worth removing.
_Chromic Iron_.--Crystals of this are included in the denser rock
in great abundance; they are very small, seldom over a few lines
in diameter, of an iron black color, of a regular octahedral form;
sometimes large crystals may be found in place or in the disintegrated
loose rock. I have seen them a half inch in diameter, and a half dozen
in a small mass, thus forming an excellent cabinet specimen. By finding
out by observation where they are the thickest in the rock, and cutting
in at this point, more or less fine crystals may be obtained. This is
readily found where they are so very abundant, near the equidistant
points of the walk, that no difficulty should be encountered in so
doing. These characteristics are interesting, and if large specimens
cannot be obtained, any quantity of the small crystals may be split out,
and, as a group, used for a representative at least. Before the blowpipe
it is infusible, but if powdered, it slowly dissolves in the molten
borax bead and yields a beautiful green globule. The specific gravity,
which is generally unattainable, is about 4.5, and hardness 5 to 6. Its
powder or small fragments are attracted by the magnet. A few small veins
of this mineral are also to be found horizontally in the rock, and
small masses may be obtained. They are very rare, however. I have seen
numerous agates from this locality, but have not found them there
myself. They may be looked for in the loose earth over the outcrop, or
along the wall of the river. Our next locality is Paterson, N. J., or
rather in a trip first to West Paterson by the D.L. & W. Railroad,
Boonton branch, then back to Paterson proper, which is but a short
distance, and then home by the Erie road, or, if an excursion ticket has
been bought, on the D.L. & W, back from West Paterson. Garret Rock holds
the minerals of Paterson, and although they are few in number, are very
unique. The first is phrenite. This beautiful mineral occurs in
geodes, or veins of them, near the surface of the basalt, which is the
characteristic formation here, and lies on the red sandstone.
These veins are but two or three feet from the surface, and the ones
from which the fine specimens are to be and have been obtained are
exposed by the railroad cutting about a thousand feet north of the
station at West Paterson, and on the west side of the rails. Near or
below the beds is a small pile of debris, prominent by being the only
one in the vicinity near the rails. In this loose rock and the veins
which are by this description readily found and identified, they are
about three inches in thickness, and in some places widen out into
pockets even a foot in diameter They look like seams of a dark earth,
with blotches of white or green matter where they are weathered, but are
fresher in appearance inside. The rock, in the immediate vicinity of the
veins, is soft, and may be readily broken out with the hammer of, if
possible, a pick bar, and thus some of these geode cavities broken into,
and much finer specimens obtained than in the vein proper. Considerable
occurs scattered about in the before-mentioned pile of loose rock and
debris, and if one does not prize it sufficiently to cut into the rock,
taking the chances of lucky find, plenty may be obtained thus; but as
it has been pretty thoroughly picked over where loose, it is much more
satisfactory to obtain the fine specimens in place in the rock. When
the bed for the railroad was being cut here, many fine specimens were
obtained by those in the vicinity, and the natives of the place have it
in abundance, and it may be obtained from many of them for a trifle, if
one is not inclined to work it out. The mineral itself occurs in masses
in the vein of a white, greenish white, or more or less dark green
color. Sometimes yellowish crystals of it occur plentifully in short
thick prisms, but the common form is that of round coralloid bunches,
having a radiated structure within. Sometimes it is in masses made up
of a structure resembling the leaves of a book slightly opened, and in
nearly every shape and size. Crystals of the various forms may be well
secured, and also the different colors from the deep green to the blue
white, always remembering that true, perfect crystals are of more value
than masses or attempted forms. The specific gravity is 2.8 to
2.9, hardness nearly 7 before the blowpipe; it readily fuses after
intumescing; it dissolves in hot acid without gelatinizing, leaving a
flaky residue.
_Datholite_.--This mineral is very abundant as inferior specimens, and
frequently very fine ones may be obtained. They occur all around Garret
Rock at the juncture of the basalt and red sandstone, in pockets, and as
heavy druses. They are most abundant near the rock cuttings between West
Paterson and Paterson, and may be cut out by patient labor. This is a
long known and somewhat noted locality for datholite, and no difficulty
need be experienced in obtaining plenty of fair specimens. Near them is
the red sandstone, lying under the basalt, and baked to a scoriaceous
cinder. Upon this is a layer of datholite in the form of a crystalline
plate, and over or above this, either in the basalt or hanging down into
cavities in the sandstone, are the crystals or geodes of datholite. Old
spots are generally exhausted, and consequently every new comer has to
hunt up new pockets, but as this is readily done, I will not expend
further comment on the matter. The datholite, as in other localities,
consists of groups of small colorless crystals. Hardness, about 5;
specific gravity, 3. Before the blowpipe it intumesces and melts to a
glassy globule coloring the flame green, and forms a jelly when boiled
with the acids.
_Pectolite_--This mineral is also quite abundant in places, the greater
part occurring with or near the phrenite before mentioned, in small
masses generally more or less weathered, but in very fair specimens,
which are about an inch in thickness. It is readily recognized by its
peculiar appearance, which, I may again repeat, is in fibrous masses,
these fibers being set together in radiated forms, and are quite tough
and flexible, of a white color, and readily fused to a globule before
the blowpipe.
_Feldspar_.--This mineral occurs strewn over the hill from place to
place, and is peculiarly characterized by its lively flesh red color,
quite different from the dull yellowish gray of that from Staten Island
or Bergen Hill. Fine crystals of it are rather rare, but beautiful
specimens of broken groups may be obtained in loose debris around the
hill and in its center. I have not been able to locate the vein or veins
from which it has come, but persistent search will probably reveal it,
or it may be stumbled upon by accident. Some of the residents of the
vicinity have some fine specimens, and it is possible that they can
direct to a plentiful locality. However, some specimens are well worth
a thorough search, and possess considerable value as mineralogieal
specimens. The specific gravity of the mineral is 2.6, and it has a
hardness of 6 before the blowpipe. It is with difficulty fused to a
globule, more or less transparent. It occurs undoubtedly in veins in the
basalt and near the surface of the outcrop As this locality has never
before been mentioned as affording this species, it is fresh to the
amateur and other mineralogists, and there need be no difficulty in
obtaining some fine specimens. Its brilliant color distinguishes it from
other minerals of the locality.
It is possible that some of the other zeolites as mentioned under Bergen
Hill occur here, but I have not been able to find them. The reason
may be that the rock is but little cut into, and consequently no new
unaltered veins are exposed.
COPPER MINES, ARLINGTON, N. J.--A short distance north of this station,
on the New York and Greenwood Lake Railroad, and about nine miles from
Jersey City, is one of the cuttings into the deposits of copper which
permeate many portions of the red sandstone of this and the allied
districts in Connecticut and Massachusetts, and which have been so
extensively worked further south at Somerville and New Brunswick, etc.
There are quite a variety of copper minerals occurring in these mines,
and as they differ but little in anything but abundance, I will describe
this, the one nearest to New York City, as I promised in commencing
these papers. The locality of this mine may be readily found, as it is
near the old turnpike from Jersey City, along which the water-pipes or
aqueduct, are laid. By taking the road directly opposite to the station
at Arlington, walking north to its end, which is a short distance, then
turning to the left along the road, there crossing and turning north up
the next road joining this, until the turnpike is reached; this is then
followed east for about a quarter-mile, passing occasional heaps in the
road of green earth, until the head of a descent is reached, when we
turn off into the field to the left, and there find the mine near the
heaps of greenish rocks and ore scattered about, a distance from the
station of about a mile and a half through a pleasing country. The
entrance to the mine is to the right of the bank of white earth on the
edge of, and in the east side of the hill; it is a tunnel more or less
caved in, running in under the heaps of rock for some distance. It will
not be necessary, even if it were safe, to venture into the mine, but
all the specimens mentioned below may be obtained from the heaps of ore
and rock outside, and in the outcrops in the east side of the hill, a
little north of the mouth of the tunnel to the mine. The hammer and cold
chisel will be necessary, and about three hours should be allowed to
stay, taking the noon train from New York there, and the 5.09 P.M. train
in return, or the 6.30 A.M. train from the city, and the 1.57 P.M. in
return. This will give ample opportunity for the selection of specimens,
and, if time is left, to visit the water works, etc.
_Green Malachite_.--This is the prominent mineral of the locality, and
is conspicuous by its rich green color on all the rocks and in the
outcrops. Fine specimens of it form excellent cabinet specimens. It
should be in masses of good size, with a silky, divergent, fibrous
structure, quite hard, and of a pure oil green color, for this purpose.
Drused crystals of it are also very beautiful and abundant, but very
minute. As the greater part of it is but a sixteenth or eighth of an
inch in thickness, it may require some searching to secure large masses
a quarter to a half-inch in thickness, but there was considerable, both
in the rock, debris, and outcrop, remaining the last visit I made to the
place a few months ago. The mineral is so characterized by its color and
solubility in acid that a detailed description of it is unnecessary to
serve to distinguish it. Its specific gravity is 4, and hardness about
4. It decrepitates before the blowpipe, but when fused with some borax
in a small hollow on a piece of wood charcoal, gives a globule of
copper. It readily dissolves in acids, with effervescence, as it is a
carbonate of copper.
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