AGRICULTURAL AND MINERAL PRODUCTIONS. 159

 

 

Other coal-fields occur in Illinois and Missouri,
in Texas, Michigan, Rhode Island, and New
Brunswick and Nova Scotia.

The area of the coal-fields of Western Europe is estimated
by Dana at about 20,000 square miles, while the total area
of those of the United States probably exceeds 125,000
square miles. In the United States, Pennsylvania possesses
the most extensive and the richest deposits, the total area
of the deposits in this State being nearly 20,000 square
miles, or equal to those of Western Europe. The richness
of the American coal-fields cannot fail to exert an import-
ant influence on the future development of the country.

418. Peat-Bogs of Massachusetts——Peat con-
sists of a black, carbonaceous deposit which ac-
cumulates in badly-drained regions of humid
climates. The surfaces of the peat-marshes are
often covered with a thin crust, formed. by the
interlacing roots of vegetable growths. Below
this crust is a treacherous, oozy quagmire.

When peat is dried it is suitable for fuel.
Dana estimates that Massachusetts contains fifteen
‘billion cubic feet of peat. Large deposits occur in

_ the Great Dismal Swamp, in North Carolina and
Virginia.
419. Petroleum, or Coal Oil, is found in various

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig, 138, Oil Well and Tank.

sections. ‘The most valuable deposits occur in a
region embracing Western Pennsylvania, Vir-
ginia, Ohio, and Michigan. Petroleum is found

also in the West.

 

 

The oil is obtained by boring. The wells so
produced are similar to artesian wells, except in
the material discharged. In many instances the
oil issues in powerful streams, which continue to
flow for considerable periods. The crude oil is
generally stored in huge tanks, from which it is
transferred to barrels or iron tanks for trans-
portation. Much is also distributed for great dis-
tances through lines of pipes called pipe-lines.
For most commercial uses it is necessary to re-
fine or purify the oil.

420. Natural Gas.——Accumulations of natural
or rock-gas occur in nearly all portions of the
United States, but such deposits are especially
rich in the regions where coal oil is found.
Western Pennsylvania, and the adjoining States,
yield great quantities of such gas.

‘The gas is obtained by borings similar to those
made for artesian wells or coal-oil wells. From
the gas wells thus formed the gas issues forth with
great velocity. When lighted it burns with a
flame similar to that of ordinary illuminating
gas. Like ordinary gas it burns with a pale
bluish flame when mixed with air, and affords
an excellent source of artificial heat.

- Natural gas has been known for many years past, but it
is only recently that its great extent and quantity have
been ascertained. In many districts—notably in the city
of Pittsburgh and vicinity—natural gas has practically
superseded illuminating gas as a source of light, and has
almost entirely replaced ordinary coal as a source of heat.
The value of such a natural product in any manufacturing
centre can scarcely be overestimated, and its successful in-
troduction in any locality has in. all cases been attended
with a marked growth in the extent and variety of its
manufactures. Although such deposits must in perhaps a
comparatively short time become exhausted, as yet they
show but little signs of failure.

The gas escapes from the well under great pressure.
Before its delivery to consumers, through pipes like ordi-
nary gas-pipes, the pressure is reduced by suitable contri-
vances; so that its consumption is not attended with any
greater risk than that attending ordinary illuminating gas.

421. Salt——Beds of rock-salt occur in Louisi-
ana, Virginia, and in various parts of the West.
Large quantities are obtained by evaporating the
waters of saline or brine springs. These are of
common occurrence. The most valuable are
found in New York, in the neighborhood of
Salina and Syracuse; in Virginia, Michigan, Ken-
tucky, and in the Far West.

422. Building Stones.—Large deposits of valu-
able building stones are found in all parts of the
country. Among the most common are various
kinds of sandstone, marble, granite, slate, mag-
nesian limestone, serpentine, gneiss, and mica