The Cadiz sentinel. [volume] (Cadiz, Ohio) 184?-1851, 1851-02-05
Agricultural GeoIeey-No. IL.
ny JOSIAH noABRouK

| Granite, hornblende, aud lime formations
constitute more than nineteen twenlielhs Of
mountain and rocky masses upon our globe
The highest peaks Of mountains aud the low
est depths Of excavations yet witnessed are
principally granite formations. Early uphea-
walls Of The earth, in i,s geological history, ate
supposed to have given to this rock-foImed
when il was snd, Let dry land appear
both the highest and the lowest position in
the pilng Of mountains.
All granite formations are composed essen
tally Of three Ingredients feldspar ,
aud mica, combined by mechanical mixture
rather than chemical combination in almost
every proportion ofthese ingredients. Quartz
is the mnsl abundan; Of the three ingredients,
and suneiimes of itself constitutes large
rocks, and even mouRiuin ranges. Fedspar,
also, in some rocky masses, is the most a.
bundant ingredient. When the rock is prn
cipalIy feIdspar, interspersed with irregular
lines Of quartz, giving ii somewhat line char
acter Of Hebrew letters, il is called graphic
granite, from The Greek word grapho, 10
write. In graphic granite The mica is entire
ly, or nearly, wanting, being composed al
most wholly Of feldspar, with slight sprnkr
ling oc quartz Snch teldspar rocks fre-
guentIy decompose by the action Of air and
water, forming porcelain clay, called by the
Chinese kdolin.
j A large deposit of feldspa'. of good
EQUALITY for china-wn'e, also for porcelain
teeth, has been opened and worked to some
extent in Wilmington. Delaware. That de-
eosi,, also one in lIaddam, Connecticut, have
furnished large quantities Of feIdspar forp p"r-
ceaiu embellishments IN this counry, in ad-
dltion TO considerable quantities exported 10
other countries for the same use.
A portion of granite formations are strait
fed, having slaiy structure. Another por
Il ton is uns.ratiRsd--l The three ingre ents
especially the mica, being thrown in every
Imaginable position. Those sraIfed are
called gneiss aud mica siale. The distinc
ton between gneiss and mica slate ist the alb
sence of feldspnr in the latter; the rock be-
ing composed Of quartz and mica, of HON,
ogeneous structure, with smooth but lre'
quently an unduating surface. Ii is more
IfriaLle, and less durable for footwaks, bridg-
es. hools, aud other purposes exposing it tc
! friction, than gness. II is also less readil,
spll, into slabs Of "a large surface, and is hence
far the most limited Of the two rocks in hei
application to purposes Of architecture.
EXPERIMENTS "A teacher in Philadelphia
} once said to his pupils: "Boys, all who hav'
! their lessons 10 day at eleven O'Clock may g
with me on geological excursion" Ever
{ boy had his lesson thoroughly at the hou
> named--the first thorough lesson ever got b.
{ several of his pupils. Similar experiment
!. continued changed bis worst scholars int
{ his best.
, In one Of the New York Public Schools
: the teacher was greatly annoyed by severa
: truant boys, drawn TO the docks Of the cit,
by the attractions upon the wharves. FL
8 at length offered to the punciual scholars ex
: ercises in drawing, also an opportunity +
form cabinets of geology for their school
their homes, and sending abroad. His in
corrigible ,runnis Immediately became hi
most punctual scholars, and the very wors
J. boy in school was soon known as an arlis
S and, as such, invited by clergyman Of III
< city 10 becume the associate and teacher {
, his children Dr. not "working schools" an
i houses of refuge forcibly illustrate the adag
! that an ounce Of prevention il better than
i pound Of curef