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Scientific American Supplement, No. 520, December 19, 1885 online

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component metals. A few of them are: Wood's alloy, consisting of:
cadmium, 1 to 2 parts; tin, 2 parts; lead, 4 parts; bismuth, 7 to 8
parts.

This alloy is fusible between 150° and 159° Fahr. The fusible metal of
D'Arcet is composed of: bismuth, 8 parts; lead, 5 parts; tin, 3 parts. It
melts at 173.3°. We can, therefore, by proper mixture, form a solder
which will melt at any desirable temperature. Numerous devices for
closing doors automatically have been constructed, all depending upon the
use of the fusible solder catch.

* * * * *




STEEL STRUCTURES.


At a recent meeting of the Engineers' Club of Philadelphia, Mr. James
Christie presented a paper upon "The Adaptation of Steel to Structural
Work." The price of steel has now fallen so low, as compared with iron,
that its increased use will be actively stimulated as the building
industries revive. The grades and properties of the steels are so
distinct and various that opinions differ much as to the adaptability of
each grade for a special purpose. Hitherto, engineers have favored open
hearth steel on account of uniformity, but recent results obtained from
Bessemer steel tend to place either make on equality. The seeming
tendency is to specify what the physical properties shall be, and not how
the steel shall be made.

For boiler and ship plates, the mildest and most ductile steel is
favored. For ships' frames and beams, a harder steel, up to 75,000 pounds
tenacity, is frequently used. For tension members of bridges, steel of
65,000 to 75,000 pounds tenacity is usually specified; and for
compression members, 80,000 to 90,000 pounds. In the Forth Bridge,
compression steel is limited to 75,000 to 82,000 pounds. Such a marked
advantage occurs from the use of high tension steel in compression
members, and the danger of sudden failure of a properly made strut is so
little, that future practice will favor the use of hard steel in
compression, unless the material should prove untrustworthy. In columns,
even as long as forty diameters, steel of 90,000 pounds tenacity will
exceed the mildest steel 35 per cent., or iron 50 per cent., in
compressive resistance.

The present uncertainty consists largely as to how high-tension steel
will endure the manipulation usual with iron without injury. A few
experiments were recently made by the writer on riveted struts of both
mild and hard steel, which had been punched, straightened, and riveted,
as usual with iron, but no indication of deterioration was found.

Steel castings are now made entirely trustworthy for tensile working
stresses of 10,000 to 15,000 pounds per square inch. In some portable
machinery, an intermittent tensile stress is applied of 15,000 pounds,
sometimes rising to 20,000 pounds per square inch of section, without any
evidence of weakness.

* * * * *

Equal volumes of amyl alcohol (rectified fusel oil) and pure concentrated
hydrochloric acid, shaken together in a test tube, unite to form a single
colorless liquid; if one volume of benzine (from petroleum) be added to
this, and the tube well shaken, the contents will soon separate into
_three_ distinct colorless fluids, the planes of demarkation being
clearly discernible by transmitted light. Drop into the tube a particle
of "acid magenta;" after again shaking the liquids together, the lower
two zones will present different shades of red, while the supernatant
hydrocarbon will remain without color.

* * * * *




A METHOD OF MEASURING THE ABSOLUTE SENSITIVENESS OF PHOTOGRAPHIC DRY
PLATES.

[Footnote: From the Proceedings of the Academy of Arts and
Sciences. - _Amer. Jour._]

By WILLIAM H. PICKERING.


Within the last few years the subject of dry plate photography has
Increased very rapidly, not only in general popularity, but also in
importance in regard to its applications to other departments of science.
Numerous plate manufacturers have sprung up in this country as well as
abroad, and each naturally claims all the good qualities for his own
plates. It therefore seemed desirable that some tests should be made
which would determine definitely the validity of these claims, and that
they should be made in such a manner that other persons using instruments
similarly constructed would be able to obtain the same results.

Perhaps the most important tests needed are in regard to the
sensitiveness of the plates. Most plate makers use the wet plates as
their standard, giving the sensitiveness of the dry plates at from two to
sixty times greater; but as wet plates vary quite as much as dry ones,
depending on the collodion, condition of the bath, etc., this system is
very unsatisfactory. Another method, employed largely in England, depends
on the use of the Warnerke sensitometer. In this instrument the light
from a tablet coated with luminous paint just after being exposed to a
magnesium light is permitted to shine through a colored transparent film
of graduated density upon the plate to be tested. Each degree on the film
has a number, and, after a given exposure, the last number photographed
on the plate represents the sensitiveness on an empirical scale. There
are two or three objections to this instrument. In the first place, the
light-giving power of the luminous tablet is liable to variations, and,
if left in a warm, moist place, it rapidly deteriorates. Again, it has
been shown by Captain Abney that plates sensitized by iodides, bromides,
and chlorides, which may be equally sensitive to white light, are not
equally affected by the light emitted by the paint; the bromides being
the most rapidly darkened, the chlorides next, and the iodides least of
all. The instrument is therefore applicable only to testing plates
sensitized with the same salts.

In this investigation it was first shown that the plates most sensitive
for one colored light were not necessarily the most so for light of
another color. Therefore it was evident that the sun must be used as the
ultimate source of light, and it was concluded to employ the light
reflected from the sky near the zenith as the direct source. But as this
would vary in brilliancy from day to day, it was necessary to use some
method which would avoid the employment of an absolute standard of light.
It is evident that we may escape the use of this troublesome standard, if
we can obtain some material which has a perfectly uniform sensitiveness;
for we may then state the sensitiveness of our plates in terms of this
substance, regardless of the brilliancy of our source. The first material
tried was white filter paper, salted and sensitized in a standard
solution of silver nitrate. This was afterward replaced by powdered
silver chloride, chemically pure, which was found to be much more
sensitive than that made from the commercial chemicals. This powder is
spread out in a thin layer, in a long paper cell, on a strip of glass.
The cell measures one centimeter broad by ten in length. Over this is
laid a sheet of tissue paper, and above that a narrow strip of black
paper, so arranged so as to cover the chloride for its full length and
half its breadth. These two pieces of paper are pasted on to the under
side of a narrow strip of glass which is placed on top of the paper cell.
The apparatus in which the exposures are made consists of a box a little
over a meter in length, closed at the top by a board, in which is a
circular aperture 15'8 cm. in diameter. Over this board may be placed a
cover, in the center of which is a hole 0.05 cm. in diameter, which
therefore lets through 0.00001 as much light as the full aperture. The
silver chloride is placed a distance of just one meter from the larger
aperture, and over it is placed the photographic scale, which might be
made of tinted gelatines, or, as in the present case, constructed of long
strips of tissue paper, of varying widths, and arranged like a flight of
steps; so that the light passing through one side of the scale traverses
nine strips of paper, while that through the other side traverses only
one strip. Each strip cuts off about one-sixth of the light passing
through it, so that, taking the middle strip as unity, the strips on
either side taken in order will transmit approximately -

1 2 3 4 5 6 7 8 9
2.0 1.65 1.4 1.2 1.0 0.85 0.7 0.6 0.5

The instrument is now pointed toward the zenith for about eight minutes,
on a day when there is a bright blue sky. On taking the apparatus into
the dark room and viewing the impression by gaslight, it will be found
that the markings, which are quite clear at one end, have entirely faded
out by the time the middle division is reached. The last division clearly
marked is noted. Five strips cut from sensitized glass plates, ten
centimeters long and two and a half in width, are now placed side by side
under the scale, in the place of the chloride. By this means we can test,
if we wish, five different kinds of plates at once. The cover of the
sensitometer containing the 0.05cm. hole is put on, and the plates
exposed to sky light for a time varying anywhere between twenty seconds
and three minutes, depending on the sensitiveness of the plates. The
instrument is then removed to the dark room, and the plates developed by
immersing them all at once in a solution consisting of four parts
potassium oxalate and one part ferrous sulphate. After ten minutes they
are removed, fixed, and dried. Their readings are then noted, and
compared with those obtained with the silver chloride. The chloride
experiment is again performed as soon as the plates have been removed,
and the first result confirmed. With some plates it is necessary to make
two or three trials before the right exposure can be found; but if the
image disappears anywhere between the second and eighth divisions, a
satisfactory result may be obtained.

The plates were also tested using gaslight instead of daylight. In this
case an Argand burner was employed burning five cubic feet of gas per
hour. A diaphragm 1 cm. in diameter was placed close to the glass
chimney, and the chloride was placed at 10 cm. distance, and exposed to
the light coming from the brightest part of the flame, for ten hours.
This produced an impression as far as the third division of the scale.
The plates were exposed in the sensitometer as usual, except that it was
found convenient in several cases to use a larger stop, measuring 0.316
cm. in diameter.

The following table gives the absolute sensitiveness of several of the
best known kinds of American and foreign plates, when developed with
oxalate, in terms of pure silver chloride taken as a standard. As the
numbers would be very large, however, if the chloride were taken as a
unit, it was thought better to give them in even hundred thousands.

SENSITIVENESS OF PLATES.

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,


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Online LibraryVariousScientific American Supplement, No. 520, December 19, 1885 → online text (page 2 of 9)