Plates. Daylight. Gaslight.
Carbutt transparency 0.7 ..
Allen and Rowell 1.3 150
Richardson standard 1.3 10
Marshall and Blair 2.7 140
Blair instantaneous 3.0 140
Carbutt special 4.0 20
Monroe 4.0 25
Wratten and Wainwright 4.0 10
Eastman special 5.3 30
Richardson instantaneous 5.3 20
Walker Reid and Inglis 11.0 600
Edwards 11.0 20
Monckhoven 16.0 120
Beebe 16.0 20
Cramer 16.0 120
It will be noted that the plates most sensitive to gaslight are by no
means necessarily the most sensitive to daylight; in several instances,
in fact, the reverse seems to be true.
It should be said that the above figures cannot be considered final until
each plate has been tested separately with its own developer, as this
would undoubtedly have some influence on the final result.
Meanwhile, two or three interesting investigations naturally suggest
themselves; to determine, for instance, the relative actinism of blue
sky, haze, and clouds; also, the relative exposures proper to give at
different hours of the day, at different seasons of the year, and in
different countries. A somewhat prolonged research would indicate what
effect the presence of sunspots had on solar radiation--whether it was
increased or diminished.
* * * * *
NATURAL GAS FUEL AND ITS APPLICATION TO MANUFACTURING
PURPOSES.
[Footnote: Read before the Iron and Steel Institute of London, May 8,
1885.]
By Mr. ANDREW CARNEGIE, New York.
In these days of depression in manufacturing, the world over, it is
specially cheering to be able to dwell upon something of a pleasant
character. Listen, therefore, while I tell you about the natural gas fuel
which we have recently discovered in the Pittsburg district. That
Pittsburg should have been still further favored in the matter of fuel
seems rather unfair, for she has long been noted for the cheapest fuel in
the world. The actual cost of coal, to such as mine their own, has been
between 4s. and 5s. per ton; while slack, which has always been very
largely used for making gas in Siemens furnaces and under boilers, has
ranged from 2s. to 2s. 6d. per ton. Some mills situated near the mines or
upon the rivers for many years received slack coal at a cost not
exceeding 1s. 6d. per ton. It is this cheap fuel which natural gas has
come to supplant. It is now many years since the pumping engines at oil
wells were first run by gas, obtained in small quantities from many of
the holes which failed to yield oil. In several cases immense gas wells
were found near the oil district; but some years elapsed before there
occurred to any one the idea of piping it to the nearest manufacturing
establishments, which were those about Pittsburg. Several years ago the
product of several gas wells in the Butler region was piped to two mills
at Sharpsburg, five miles from the city of Pittsburg, and there used as
fuel, but not with such triumphant success as to attract much attention
to the experiment. Failures of supply, faults in the tubing, and
imperfect appliances for use at the mills combined to make the new fuel
troublesome. Seven years ago a company drilled for oil at Murraysville,
about eighteen miles from Pittsburg. A depth of 1,320 feet had been
reached when the drills were thrown high in the air, and the derrick
broken to pieces and scattered around by a tremendous explosion of gas.
The roar of escaping gas was heard in Munroville, five miles distant.
After four pipes, each two inches in diameter, had been laid from the
mouth of the well and the flow directed through them, the gas was
ignited, and the whole district for miles round was lighted up. This
valuable fuel, although within nine miles of our steel-rail mills at
Pittsburg, was permitted to waste for five years. It may well be asked
why we did not at once secure the property and utilize this fuel; but the
business of conducting it to the mills and there using it was not well
understood until recently. Besides this, the cost of a line was then more
than double what it is now; we then estimated that £140,000 would be
required to introduce the new fuel. The cost to-day does not exceed
£1,500 per mile. As our coal was not costing us more than 3s. per ton of
finished rails, the inducement was not in our opinion great enough to
justify the expenditure of so much capital and taking the risk of failure
of the supply. Two years ago men who had more knowledge of the oil-wells
than ourselves had sufficient faith in the continuity of the gas supply
to offer to furnish us with gas for a sum per year equal to that hitherto
annually paid for coal until the amount expended by them on piping had
been repaid, and afterward at half that sum. It took us about eighteen
months to recoup the gas company, and we are now working under the
permanent arrangement of one-half the previous cost of fuel on cars at
work. Since our success in the use of this new natural fuel at the rail
mills, parties still bolder have invested in lines of piping to the city
of Pittsburg, fifteen to eighteen miles from the wells. The territory
underlain with this natural gas has not yet been clearly defined. At the
principal field, that of Murraysville (from which most of the gas is
obtained to-day), I found, upon my visit to that interesting region last
autumn, that nine wells had been sunk, and were yielding gas in large
quantities. One of these was estimated as yielding 30,000,000 cubic feet
in 24 hours. This district lies to the northeast of Pittsburg, running
southward from it toward the Pennsylvania Railroad. Gas has been found
upon a belt averaging about half a mile in width for a distance of
between four and five miles. Beyond that again we reach a point where
salt water flows into the wells and drowns the gas. Several wells have
been bored upon this belt near the Pennsylvania Railroad, and have been
found useless from this cause. Geologists tell us that in this region a
depression of 600 feet occurs in the strata, but how far the fault
extends has not yet been ascertained. Wells will no doubt soon be sunk
southward of the Pennsylvania Railroad upon this half-mile belt. Swinging
round toward the southwest, and about twenty miles from the city, we
reach the gas fields of Washington county. The wells so far struck do not
appear to be as strong as those of the Murraysville district, but it is
possible that wells equally productive may be found there hereafter.
There are now four wells yielding gas in the district, and others are
being drilled. Passing still further to the west, we reach another gas
territory, from which manufacturing works in Beaver Falls and Rochester,
some twenty-eight miles west of Pittsburg, receive their supply.
Proceeding with the circle we are drawing in imagination around
Pittsburg, we pass from the west to the southwest without finding gas in
any considerable quantity, until we reach the Butler gas field,
equidistant from Pittsburg on the northwest, with Washington county wells
on the southwest. Proceeding now from the Butler field to the Allegheny
River, we reach the Tarentum district, still about twenty miles from
Pittsburg, which is supplying a considerable portion of the gas used.
Drawing thus a circle around Pittsburg, with a radius of fifteen to
twenty miles, we find four distinct gas-producing districts. In the city
of Pittsburg itself several wells have been bored; but the fault before
mentioned seems to extend toward the center of the circle, as salt water
has rushed in and rendered these wells wholly unproductive, though gas
was found in all of them.
I spent a few days very pleasantly last autumn driving with some friends
to the two principal fields, the Murraysville and the Washington county.
In the former district the gas rushes with such velocity through a 6-inch
pipe, extending perhaps 20 feet above the surface, that it does not
ignite within 6 feet of the mouth of the pipe. Looking up into the clear
blue sky, you see before you a dancing golden fiend, without visible
connection with the earth, swayed by the wind into fantastic shapes, and
whirling in every direction. As the gas from the well strikes the center
of the flame and passes partly through it, the lower part of the mass
curls inward, giving rise to the most beautiful effects gathered into
graceful folds at the bottom--a veritable pillar of fire. There is not a
particle of smoke from it. The gas from the wells at Washington was
allowed to escape through pipes which lay upon the ground. Looking down
from the roadside upon the first well we saw in the valley, there
appeared to be an immense circus-ring, the verdure having been burnt and
the earth baked by the flame. The ring was quite round, as the wind had
driven the flame in one direction after another, and the effect of the
great golden flame lying prone upon the earth, swaying and swirling with
the wind in every direction, was most startling. The great beast
Apollyon, minus the smoke, seemed to have come forth from his lair again.
The cost of piping is now estimated, at the present extremely low prices,
with right of way, at £1,600 sterling per mile, so that the cost of a
line to Pittsburg may be said to be about £27,000 sterling. The cost of
drilling is about £1,000, and the mode of procedure is as follows: A
derrick being first erected, a 6 inch wrought-iron pipe is driven down
through the soft earth till rock is reached from 75 to 100 feet. Large
drills, weighing from 3,000 to 4,000 lb., are now brought into use; these
rise and fall with a stroke of 4 to 5 feet. The fuel to run these drills
is conveyed by small pipes from adjoining wells. An 8-inch hole having
been bored to a depth of about 500 feet, a 5-5/8 inch wrought-iron pipe
is put down to shut off the water. The hole is then continued 6 inches in
diameter until gas is struck, when a 4-inch pipe is put down. From forty
to sixty days are consumed in sinking the well and striking gas. The
largest well known is estimated to yield about 30,000,000 cubic feet of
gas in twenty-four hours, but half of this may be considered as the
product of a good well. The pressure of gas as it issues from the mouth
of the well is nearly or quite 200 lb. per square inch. One of the gauges
which I examined showed a pressure of 187 lb. Even at works where we use
the gas nine miles from the well, the pressure is 75 lb. per square inch.
At one of the wells, where it was desirable to have a supply of pure
water, I found a small engine worked by the direct pressure of the gas as
it came from the well; and an excellent supply of water was thus obtained
from a spring in the valley. Eleven lines of pipe now convey gas from the
various wells to the manufacturing establishments in and around
Pittsburg. The largest of these for the latter part of the distance is 12
inches in diameter. Several are of 8 inches throughout. The lines
originally laid are 6 inches in diameter. Many of the mills have as yet
no appliances for using the gas, and much of it is still wasted. It is
estimated that the iron and steel mills of the city proper require fuel
equal to 166,000 bushels of coal per day; and though it is only two years
since gas was first used in Pittsburg, it has already displaced about
40,000 bushels of coal per day in these mills. Sixty odd glass works,
which required about 20,000 bushels of coal per day, mostly now use the
natural gas. In the work around Pittsburg beyond the city limits, the
amount of coal superseded by gas is about equal to that displaced in the
city. The estimated number of men whose labor will be dispensed with in
Pittsburg when gas is generally used is 5,000. It is only a question of a
few months when all the manufacturing carried on in the district will be
operated with the new fuel. As will be seen from the analyses appended to
this paper, it is a much purer fuel than coal; and this is a quality
which has proved of great advantage in the manufacture of steel, glass,
and several other products. With the exception of one, and perhaps two
concerns, no effort has been made to economize in the use of the new
fuel. In our Union Iron Mills we have attached to each puddling furnace a
small regenerative appliance, by the aid of which we save a large
percentage of fuel. The gas companies will no doubt soon require
manufacturers to adopt some such appliance. At present, owing to the
fact that there is a large surplus constantly going to waste, they allow
the gas to be used to any extent desired. Contracts are now made to
supply houses with gas for all purposes at a cost equal to that of the
coal bill for the preceding year. In the residences of several of our
partners no fuel other than this gas is now used, and everybody who has
applied it to domestic purposes is delighted with the change from the
smoky and dirty bituminous coal. Some, indeed, go so far as to say that
if the gas were three times as costly as the old fuel, they could not be
induced to go back to the latter. It is therefore quite within the region
of probability that the city, now so black that even Sheffield must be
considered clean in comparison, may be so revolutionized as to be the
cleanest manufacturing center in the world. A walk through our rolling
mills would surprise the members of the Institute. In the steel rail
mills for instance, where before would have been seen thirty stokers
stripped to the waist, firing boilers which require a supply of about 400
tons of coal in twenty-four hours--ninety firemen in all being employed,
each working eight hours--they would now find one man walking around the
boiler house, simply watching the water gauges, etc. Not a particle of
smoke would be seen. In the iron mills the puddlers have whitewashed the
coal bunkers belonging to their furnaces. I need not here say how much
pleasure it will afford me to arrange that any fellow members of the
Institute who may visit the republic are afforded an opportunity to see
for themselves this latest and most interesting development of the fuel
question. Good Mother Earth supplies us with all the fuel we can use and
more, and only asks us to lead it under our boilers and into our heating
and puddling furnaces, and apply the match. During the winter several
explosions have occurred in Pittsburg, owing to the escape of gas from
pipes improperly laid. The frost having penetrated the earth for several
feet and prevented escape upward, the freed gas found its way into the
cellars of houses, and, as it is odorless, its presence was not detected.
This resulted in several alarming explosions; but the danger is to be
remedied before next year. Lower pressure will be carried in the pipes
through the city, and escape pipes leading to the surface will be placed
along the surface at frequent intervals. In the case of manufacturing
establishments, the gas is led into the mills overhead, and, all the
pipes being in the open air, no danger of explosion is incurred.
The following extract from the report of a committee, made to the
American Society of Mechanical Engineers at a recent meeting, gives an
idea of the value of the new fuel: "Natural gas, next to hydrogen, is the
most powerful of the gaseous fuels, and, if properly applied, one of the
most economical, as very nearly its theoretical heating power can be
utilized in evaporating water. Being so free from all deleterious
elements, notably sulphur, it makes better iron, steel, and glass than
coal fuel. It makes steam more regularly, as there is no opening of
doors, and no blank spaces are left on the grate bars to let cold air in,
and, when properly arranged, regulates the steam pressure, leaving the
man in charge nothing to do but to look after the water, and even that
could be accomplished if one cared to trust to such a volatile
water-tender. Boilers will last longer, and there will be fewer
explosions from unequal expansion and contraction, due from cold draughts
of air being let in on hot plates.
"An experiment was made to ascertain the value of gas as a fuel in
comparison with coal in generating steam, using a retort or boiler of 42
inches diameter, 10 feet long, with 4 inch tubes. It was first fired with
selected Youghiogheny coal, broken to about 4 inch cubes, and the furnace
was charged in a manner to obtain the best results possible with the
stack that was attached to the boiler. Nine pounds of water evaporated to
the pound of coal consumed was the best result obtained. The water was
measured by two meters, one in the suction and the other in the
discharge. The water was fed into a heater at a temperature of from 60°
to 62°; the heater was placed in the flue leading from the boiler to the
stack in both gas and coal experiments. In making the calculations, the
standard 76 lb. bushel of the Pittsburg district was used. Six hundred
and eighty-four pounds of water were evaporated per bushel, which was
60.9 per cent. of the theoretical value of the coal. Where gas was burned
under the same boiler, but with a different furnace, and taking 1 lb. of
gas to be 2.35 cubic feet, the water evaporated was found to be 20.31
lb., or 83.4 per cent. of the theoretical heat units were utilized. The
steam was under the atmospheric pressure, there being a large enough
opening to prevent any back pressure, the combustion of both gas and coal
was not hurried. It was found that the lower row of tubes could be
plugged and the same amount of water could be evaporated with the coal;
but with gas, by closing all the tubes--on the end next the stack--except
enough to get rid of the products of combustion, when the pressure on the
walls of the furnace was three ounces, and the fire forced to its best,
it was found that very nearly the same results could be obtained. Hence
it was concluded that the most of the work was done on the shell of the
boiler."
In no other way can I give the members of the Iron and Steel Institute so
much information in regard to this new fuel as by including in this paper
a very able communication from the chief chemist at our Edgar Thomson
Steel Works, Mr. S.A. Ford, who is to-day the highest authority upon the
subject:
"So much has been claimed for natural gas as regards the superiority of
its heating properties as compared with coal, that some analyses of this
gas, together with calculations showing the comparison between its
heating power and that of coal, may be of interest. These calculations
are, of course, theoretical in both cases, and it must not be imagined
that the total amount of heat, either in a ton of coal or 1,000 cubic
feet of natural gas, can ever be fully utilized. In making these
calculations I employed as a basis what in my estimation was a gas of an
average chemical composition, as I have found that gas from the same well
varies continually in its composition. Thus, samples of gas from the same
well, but taken on different days, vary in nitrogen from 23 per cent. to
_nil_, carbonic acid from 2 per cent. to _nil_, oxygen from 4 per cent,
to 0.4 per cent., and so with all the component gases. Before giving the
theoretical heating power of 1,000 cubic feet of this gas I will note a
few analyses. The first four are of gas from the same well; samples
taken on the same day that they were analyzed. The two last are from two
different wells in the East Liberty district: