The morning news. [volume] (Savannah, Ga.) 1887-1900, 1891-10-21

the citizens Of Middletown voted that who-
ever shall dig or raise stone at ye rocks on
the east side OF the river now Portland) for
any without the town, the said digger shall
be none but an inhabitant Of Middletown,
and shall be responsible 10 ye towne -
pence per tunn for every tunn OF stones
that he or they shall digg for any person
whosoever without the towne.'"
''What about slate for roofing purposesg'
THAT is also al industry of recent origin,
and few Of the slate quarries have been in
operation more than twenty or thirty years
The prevalence of the slate tombstones.
however, in many Of our older churchyards
would seem to indicate that these stones
| have been quarried from a much earlier
period for other purposes than roofing
| ITO what extent are building stones af-
fected by heat and coldF'
| CONDUCTING POWER AND ELASTICITY.
''Stones, as a rule, possess but a low con-
Quoting power and slight elasticity. They
are aggregates of minerals more or less
closely cohering, each OF which possess de-
| grees OF expansion and contraction of its
own. As our temperature is ever chang
| ing, and within the space of twenty-four
| hours may vary as much as 40S so within
| the mass OF stone there in continual move
ment among its psrticles. Slight as these
movements may be, slow and gradual
weakening and disintegration must en-
| euc. linus bunker I'LL monument.
| q hollow granite obelisk 22l feet high by 90
feet square at the base. swings from side to
| side with tho progress of the sun during a
| sunny day, so that pendulum suspended
| from the center of the top describes an ir-
regular elipse nearly half an iuch in great
est diameter. Similar effects, but in less
marked degree, have been observed on the
south and west sides Of the Smithsonian
building. The effects of moderate tenn
| naratilraQ ~ ordinary
are, however, slight when compared
with the destructive energies of
| freezing temperatures upon stones
saturated with moisture. At temperature
of 30 Fahrenheit the pressure exerted by
water passing from liquid to solid state
| amounts to 1873 tons to the square foot, or
equal to the weight of column of ice a
mile high. Is it then astonishing that
porous sandstone exposed in a
house front to be saturated with
| a winters rain and then subject to tenn
| perstures perhaps several degrees below the
freezing point shows signs of weakness and
| exfoliation after a single seasons exposure?
Hence the conclusion Is natural that those
| stones are the most durable which will abb
| serb and retain the least moisture"
How doiyou test the power of stones to
withstand the effects of frostg'
| The best method is to actually expose
| prepared blocks to such a temperature,
| when saturated with water as TO freeze
| them sold, and then notice the amount of
disintegration or loss In strength. OF
course, at all seasons of the year this cannot
be done, and artificial methods must be
used"
| RESISTANCE TO HEAT,
What building stones best resist heat?n
"The injurious effects of artificial heat,
such as is produced by burning building,
are. of course, greater il proportion as the
temperature is higher. Sufficient and re-
| liable daJa cannot be had for accurately
estimating the comparative enduring power
OF stones under these circumstances. 1t
seems, however, to be we'll proven that of
all stones granite is the least fire proof,
while the fact that certain of the fine
grained siliceous sandstones are used
for furnace backing would seem
to show that if not absolutely
flre-proof they are very nearly
SO. 1t must. however, be understood that
the sudden coating Of the surface of a
heated stone. caused by repeated dashes of
cold water, has often more to do with its
disintegration than heat alone. Granite
was for long time popularity believed to
be nearly fire-proof material. The great
fires of Portland, Boston and Chicago not
merely exploded this idea, but proved the
contrary to be true-that instead
OF being the most fre-prcof it
| was Guo lthSb TdukluS OelOW elJu6E
sand or lime stone. The peculiar
susceptibility of this stone to the effect of
heat may be ascribed to its compact and
complex structure, each of its constituent
materials possessing different degrees OF ex-
panGiou. 1t has also been suggested by
certain authors that the minute water-filled
cavities in the quartz of these rocks may be
an important factor, since, when highly
heated, the water is converted into steam
and an explosion results, causing the quartz
to fly in fragments"
LIFE OF BUILDING STONES.
what is the maximum number Of years
that stones have been found to last without
discooratfon or disintegration9"
1.-THE life of building stones, OF course.
varies largely aud the following table may
be of public interest;
Life in years.
Coarse brown stone. Observation-Disclosures. to IS
Fine laminated brown stone. ........ 20 to 50
Blue stone (sandstoneJ untried, probably cen
| turtles.
Nova Scotia sandstone. untried.
| possibly .....,..-......,.... % to 2US
Ohio sandstone (best sihceousJ from one
to many centuries.
Coarse fosSiliferous limestone. ...... % TO %
Fine volitic Frenchl limestone. 30 to 10
Marble (coa Sc dolomiticJ. .......... DO
Marble Zine dolomitic). -...... 60 to 20
Maroie (nne) ........... ...,....+.. oU TO 100
Gneiss fifty years to many centuries.
us serpe1tine much used as building
materialf'
20. yes" said Prof. Merrill, sit is in great
favor. 1t is a soft, though somewhat tough,
compact rock of variable color, usually
greenish, although often variously streaked
aud spotted with yellow. yellowish green.
brownish, or more rarely red The name
serpentine is from the Latin
serpentines, q serpent, owing to its
color and spotted appearance. Owing to
its softness, which is such that it can be
readily carved or turned on lathe, and Its
beautiful colors when polished, serpentine
has long been favorite with all civilized
nations for ornaments and interior decora-
tive work. Serpentine, however, for o-na-
mental work is at the present time scarcely
ever quarried in the United States. al
though inexhaustible quantities are found
in many instances and of exceptionally fine
quality"
| NTEDTCAV