The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1884-03-08
BUILDING STONE.
W. II, Pcnnelps I.tcture in the Working
mems Course.

Wlllism H. Pennell, Esq, delivered very
Interesting lecture last evening in Mechanics
Hall, IN the Workingmen's course. The
speakers subject was Building Stone"
which involved study Of the rocks and min
erals OF this locality, aud was highly appre-
ciatsd By good sized audience.
After describing the granite of our State
and the manner Of cutting aud polishing, Mr..
Pencil spoke of the rocks in our vicinity.
Rocks are sometimes designated from the
manner OF their formation. Thus those like
trap or basalt are called intrusive or igneous;
those formed in beds like hardened clay are
called sedlmentary-or formed from sediment.
There is no doubt but that this was the maui
ner OF the formation of our rocks, laying hori-
zontal ia regular beds, varying in material as
the deposit varied and then changed By pres
sure into rocks as we see them, hardened by
the heat caused by pressure and the chemical
action induced by the heat. These rocks
were originally laid horizontal, as are all sedi-
mentary rocks. You will occasionally see
veins OF trap or basslt pushed up from below,
cutting across the veias of the older rocks,
sometlmes in one direction, sometimes in
another, but always irregular in size and out
line. With these veins of trap VS. have
nothing to do tonight, since they cannot be
called building stone.
You may remember the vein of trap near
Portland Head light that has been washed out
leaving Just an immense cut through the rocks.
In the rocks of Portland and vicinity are
found localities ghere the rocks are so twisted
and contorted as though bg some superhuman
power that they have no regular form and they
will break IN one dirtctio as well as another.
In these rocks are found veins and pockets of
quartz, Of no great extent, bat in some parts
of the city are much more prevalent than
otherS. These quartz veins in Tocuss rocks
are the gold bearing veius OF Nova Scotia aud
Australia. Some OF the rocks in our vicinity
are so black as to look like anthracite coal,
Tbs is especially the case in Cape Elizabeth.
There was even an organized effort made
here to 0ore for coal from the strong resetn-
bance OF the rock TO the shale overyiug tho
coal.
Rocks OF this class are never found in prox
unity to coal veins. They are called plumba,
gnous states from the large amount of
plambaso contained ia them. / told you the
rocks we're formed in beds laying horix ,atal
they have been tilted up until they stand on
edge so that II you wonld fnd how the rocks
overlying or underlying any particular LOCAL
iIy you'd look you have ouly to walk Nor b
or South across the layers aud you have it
bef re you. Ia this way you may also ascer-
tain the depth of any particular layer BY
measuring across The layer instead of boring
down through hundreds of feet of solid rocks.
Ignorance OF these facts allowed the men
who were looking for coal to select a promis-
ing locality and bore down between the layers.
They had more experience and less money
when they got through with the experiment.
On the other side of the city, iu Desiring.
the rocks change into mica schist and from
that into gneiss. iulerspsrsed with veins Of
| quartz or trap.
Sometimes the rocks seem to have feen
fragments of some older rocks that have been
broken up into irregular pieces. larger or
smaller, by some convuision of nature, and
they Seem to have been cemented together
again into new combinations.
This, as you will readily see, would make
stones SO rough that they can not be called
building stone.
Specimens Of cut stone from the various
| qusrries in the State we're exhibited the kind
OF work each was fitted for was spoken f.
aud large varil t. Of specimens of rock from
the cabinet in the school building was ust d
illustrating all the points brought out in The
| lecture