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Scientific American Supplement, No. 841, February 13, 1892 online

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on its surface. No anode appears ever to have been invented that is at
all suitable for working on a large scale, and the successful
introduction of this compound anode, therefore, constitutes a marked
advance in the apparatus used in electrolytic methods of production.

The apparatus by which the new process is being successfully
demonstrated on a working scale has been put up by the Caustic Soda
and Chlorine Syndicate, London, and has been in operation for several
months past. The installation consists of five large electrolytic
vessels, each of which is fitted up with five anodes and six cathodes
arranged alternately. The anodes and cathodes are separated by the
special diaphragms, and each vessel is thus divided into ten anode or
chlorine sections and ten cathode or caustic soda sections. The anodes
and cathodes in each vessel are connected up in parallel similar to an
ordinary storage battery, but the five electrolytic vessels are
connected up in series. The current is produced by an Elwell-Parker
dynamo, and the electromotive force required to overcome the
resistance of each vessel is about 4.4 volts, with a current density
of 10 amperes per square foot of electrode surface. The anode
sections, numbering fifty altogether, are connected by means of tubes,
the inlet being at the bottom and the outlet at the top of each
section. The whole of the cathode sections are connected in the same
manner. In commencing operations, the electrolytic vessels are charged
with a solution of common salt, through which a current of electricity
is then passed, thus decomposing or splitting up the salt into its
elements, chlorine and sodium. In the separation of the sodium,
however, a secondary action takes place, which converts it into
caustic soda. An automatic circulation of the solutions is maintained
by placing the charging tanks at a slight elevation, and the vessels
themselves on platforms arranged in steps. The solutions are pumped
back from the lowest vessel to their respective charging tanks, the
salt solution to be further decomposed and the caustic soda solution
to be further concentrated. The chlorine gas evolved in the fifty
anode sections is conveyed by means of main and branch tubes into
several absorbers, in which milk of lime, kept in a state of
agitation, takes up the chlorine, thus making it into bleaching or
chlorate liquor as may be required. If the chlorine is required to be
made into bleaching powder, then it is conveyed into leaden chambers
and treated with lime in the usual manner. The caustic soda formed in
the fifty cathode sections is more or less concentrated according to
the particular purpose for which it may be required. If, however, the
caustic soda is required in solid form, and practically free from
salt, then the caustic alkaline liquor is transferred from the
electrolytic vessels to evaporating pans, where it is concentrated to
the required strength by evaporation and at the same time the salt
remaining in the solution is eliminated by precipitation.

Such is the method of manufacturing caustic soda and chlorine by this
process, which will doubtless have a most important bearing upon many
trades and manufactures, more particularly upon the paper, soap, and
bleaching industries. But the invention does not stop where we have
left it, for it is stated that the process can be applied to the
production of sodium amalgam and chlorine for extracting gold and
other metals from their ores. It can also be utilized in the
production of caustic and chlorate of potash and other chemicals,
which can be manufactured in a state of the greatest purity. A very
important consideration is that of cost, for upon this depends
commercial success. It is therefore satisfactory to learn that the
cost of production has been determined by the most careful electrical
and analytical tests, which demonstrate an economy of over 50 per
cent. as compared with present methods. Highly favorable reports on
the process have been made by Dr. G. Gore, F.R.S., the eminent
authority on electro-chemical processes, by Mr. W.H. Preece, F.R.S.,
and by Messrs. Cross & Bevan, consulting chemists. Dr. Gore states
that the chemical and electrical principles upon which this process is
based are thoroughly sound, and that the process is of a
scientifically practical character. Should, however, the economy of
production even fall somewhat below the anticipations of those who
have examined into the process very carefully, it can hardly fail to
prove as successful commercially as it has scientifically.

* * * * *




COMPLETION OF THE MERSEY TUNNEL RAILWAY.


On the 11th of January (says the _Liverpool Daily Post_) will be
opened for traffic the new station of the Mersey Tunnel Railway at the
bottom of Bold Street. With the completion of the station at Bold
Street the scheme may be said to have been brought successfully to a
conclusion. It was not until 1879, after the expenditure of
125,000_l._ upon trial borings, that the promoters ventured to appeal
to the public for support, and that a company, of which the Right Hon.
H. Cecil Raikes, M.P., was chairman, was formed for carrying the
project of the Mersey Railway into effect. The experience of the
engineers in the construction of the tunnel is not a little curious.
It was proved by the borings that the position in which the tunnel was
proposed to be bored was not only the most important from the point of
view of public convenience, and therefore of commercial advantage, but
was from the point of view of engineering difficulty decidedly the
most preferable. In this position the cuttings passed through the
sandstone rock, although on the Liverpool side the shafts were sunk
through a considerable depth through "made" ground, the whole of Mann
Island and the Goree being composed of earth and gravel tipped on the
old bank of the river. Indeed the miners passed through the cellars of
old houses and unearthed old water pipes; excavated through a depth of
tipped rubbish on which these houses had evidently been built; and
then came upon the former strand of the river, beneath which was the
blue silt usually found; then a stratum of bowlder clay; and finally
the red sandstone rock. Once begun, the works were pushed forward
night and day, Sundays excepted, until January, 1884, when the last
few feet of rock were cleared away by the boring machine, and the
mayors of Liverpool and Birkenhead met in fraternal greeting beneath
the river. The operations gave employment to 3,000 men working three
shifts of eight hours each, but were greatly accelerated by the use of
Colonel Beaumont's boring machine, on which disks of chilled iron are
set in a strong iron bar made to revolve by means of compressed air.
This machine scooped out a tunnel 7 feet in diameter; and by
successive improvements Colonel Beaumont attained a speed of 150 feet
per week, leaving the old method of blasting far behind. As the
machine moved forward the rock behind was broken out to the size of
the main tunnel and bricked in in short lengths. One remarkable
circumstance in connection with the work is that the boring from the
Birkenhead side and the boring from Liverpool were found, when they
were completed and joined, to be out of line by only 1 inch.

This excellent result was attained by careful calculations and
experiments with perpendicular wires kept in position by weights,
which, to avoid oscillation, were suspended in buckets of water. From
shaft to shaft the tunnel is 1,770 yards in length and 26 feet in
diameter; but for a length of 400 feet at the James Street and
Hamilton Square stations the arch is enlarged to 50½ feet. The tunnel
is lined with from six to eight rings of solid brickwork embedded in
cement, the two inner rings being blue Staffordshire or Burnley
bricks. For the purpose of ventilation a smaller tunnel, 7 feet in
diameter, was bored parallel with the main tunnel, with which it is
connected in eight places by cross cuts, provided with suitable doors.
Both at Liverpool and at Birkenhead there are two guibal fans, one 40
feet and the other 30 feet in diameter. The smaller, which throw each
180,000 cubic feet of air per minute, ventilate the continuations of
the tunnel under Liverpool and Birkenhead respectively, and the larger
tunnel under the river. The fans remove together 600,000 cubic feet of
air per minute, and by this combined operation the entire air in the
tunnel is changed once in every seven minutes. By the use of
regulating shutters the air passes in a continuous current and the
fans are noiseless. The telegraph and telephone wires pass through the
tunnel, thus avoiding the long detour by Runcorn. Probably, as a feat
of engineering, the construction of the new station at Bold Street is
not inferior to any part of the scheme advanced. Under very singular
and perplexing difficulties it could only be proceeded with in its
first stages from midnight until six o'clock the following morning, it
being of course essential that the traffic at the Central Station
should not be interfered with. During these hours, night after night,
trenches were cut at intervals of 10 feet across the roadway
connecting the arrival platforms at the station, and into these were
placed strong balks of timber, across which planks were laid as a
temporary roadway. Beneath these planks, which were taken up and put
down as required, the rock was excavated to a depth of 9 feet, and the
balks supported upon stout props. Then from the driftway or rough
boring beneath well holes were bored to the upper excavation, and
through them the strong upright iron pillars designed to support the
roof of the new tunnel station were passed, bedded and securely fixed
in position. No sooner were they _in situ_ than the most troublesome
part of the task was entered upon, for the balks had then to be
removed in order to allow to be placed in position the girders running
the length of the new station, and resting on the tops of the upright
pillars. From these longitudinal girders cross girders of great
strength were placed, and between these were built brick arches,
packed above with concrete. This formed the roof of the new station.
One portion of it passed under the rails in the station above, and had
to be constructed without stoppage of the traffic. The rails had
consequently to be supported on a temporary steel bridge of ingenious
design, constructed by Mr. C.A. Rowlendson, the resident engineer and
manager of the company, under whose personal supervision, as
representing Sir Douglas Fox, the work has been carried out. With this
device the men were enabled to go on in safety although locomotives
were passing immediately above their heads. After the completion of
the roof the station below was excavated by what is technically called
"plug and feather" work - that is to say, by drilling holes into which
powerful wedges are driven to split the rock.

* * * * *




A STEAM STREET RAILWAY MOTOR.


[Illustration: North Chicago Street Railroad Engine]

While in Paris, President Yerkes, of the North Chicago Street Railway
Company, purchased a noiseless steam motor, the results in
experimenting with which will be watched with great interest. The
accompanying engraving, for which we are indebted to the _Street
Railway Review_, gives a very accurate idea of the general external
appearance. The car is all steel throughout, except windows, doors and
ceiling. It is 12 ft. long, 8 ft. wide, and 9 ft. high, and weighs
about seven tons. The engines, which have 25 horse power and are of
the double cylinder pattern, are below the floor and connected
directly to the wheels. The wheels are four in number and 31 in. in
diameter. The internal appearance and general arrangement of
machinery, etc., is about that of the ordinary steam dummy. It will
run in either direction, and the exhaust steam is run through a series
of mufflers which suppress the sound, condense the steam and return
the water to the boiler, which occupies the center of the car. The
motor was built in Ghent, Belgium, and cost about $5,000, custom house
duties amounting to about $2,000 more. - _The Railway Review_.

* * * * *




TWENTY-FOUR KNOT STEAMERS.


Probably the most important form of steam machinery is the marine
engine, not only because of the conditions under which it works, but
because of the great power it is called upon to exert. Naturally its
most interesting application is to Atlantic steaming. The success of
the four great liners, Teutonic, Majestic, City of Paris and City of
New York, has stimulated demand, and the Cunard Company has resolved
to add to its fleet, and place two ships on the Atlantic which will
outstrip the racers we have named.

The visitor to the late Naval Exhibition interested in shipping will
have remarked at each of the several exhibits of the great firms a
model of a projected steamer, intended to reduce the present record of
the six days' voyage across the Atlantic - the _ne plus ultra_ at this
time of steam navigation. To secure this present result a continuous
steaming for the six days at 20 knot speed is requisite, not to
mention an extra day or two at each end of the voyage. The City of
Paris and the City of New York, Furst Bismarck, Teutonic and Majestic
are capable of this, with the Umbria and Etruria close behind at 18 to
19 knots. Only ten years ago the average passage, reckoned in the same
way as from land to land - or Queenstown to Sandy Hook - was seven days
with a speed of 17 knots, the performance of such vessels as the
Arizona and Alaska. Twenty years ago the length of the voyage was
estimated as seven and a half to eight days at a speed of 16 knots,
the performance of such vessels as the Germanic and Britannic of the
White Star fleet of 5,000 tons and 5,000 horse power. Thirty years ago
the paddle steamer was not yet driven off the ocean, and we find the
Scotia crossing in between eight and nine days, at a speed of 13 or 14
knots. In 1858 ten and a half to twelve and a half days was allowed
for the passage between Liverpool and New York. So as we recede we
finally arrive at the pioneer vessels, the Sirius and Great Western,
crossing in fourteen to eighteen days at a speed of 6 to 8 knots. For
these historical details an interesting paper may be consulted, "De
Toenemende Grootte der Zee-Stoombooten," 1888, by Professor A. Huet,
of the Delft Polytechnic School.

Each of the last two or three decades has thus succeeded, always,
however, with increasing difficulty, in knocking off a day from the
duration of the voyage. But although the present six-day 20 knot boats
are of extreme size and power, and date only from the last two or
three years, still the world of travelers declares itself unsatisfied.
Already we hear that another day must be struck off, and that five-day
steamers have become a necessity of modern requirements, keeping up a
continuous ocean speed of 23½ knots to 24 knots. Shipbuilders and
engineers are ashamed to mention the word _impossible_; and designers
are already at work, as we saw in the Naval Exhibition, but only so
far in the model stage; as the absence of any of the well known
distinguishing blazons of the foremost lines was sufficient to show
that no order had been placed for the construction of a real vessel.
It will take a very short time to examine the task of the naval
architect required to secure these onerous and magnificent conditions,
five days' continuous ocean steaming at a speed of 24 knots.

The most practical, theory-despising among them must for the nonce
become a theorist, and argue from the known to the unknown; and,
first, the practical man will turn - secretly perhaps, but wisely - to
the invaluable experiments and laws laid down so clearly by the late
Mr. Froude. Although primarily designed to assist the Admiralty in
arguing from the resistance of a model to that of the full size
vessel, the practical man need not thereby despise Froude's laws, as
he is able to choose his mode: to any scale he likes, and he can take
his experiments ready made by practice on a large scale, as Newton
took the phenomena of astronomy for the illustration of the mechanical
laws. Suppose then he takes the City of Paris as his model, 560 ft. by
63 ft., in round numbers 10,000 tons displacement, and 20,000 horse
power, for a speed of 20 knots, with a coal capacity of 2,000 tons,
sufficient, with contingencies, for a voyage of six to eight days. Or
we may take a later 20 knot vessel, the Furst Bismarck, 500 ft. by
50ft., 8,000 tons, and 16,000 horse power, speed 20 knots, and coal
capacity 2,700 tons, to allow for the entire length of voyage to
Germany.

In Froude's method of comparison the laws of mechanical similitude are
preserved if we make the displacements of the model and of its copy in
the ratio of the sixth power of the speeds designed, or the length as
the square of the speed. Our new 24 knot vessel, taking the City of
Paris as a model, would therefore have 10,000 (24 ÷ 20)^{6} = 29,860,
say 30,000 tons displacement, and would be 800 ft. × 90 ft. in
dimensions. The horse power would have to be as the _seventh_ power of
the speed, and our vessel would therefore have 20,000 (24 ÷ 20)^{7},
or say 72,000 horse power. Further applications of Froude's laws of
similitude will show that the steam pressure and piston speed would
have to be raised 20 per cent., while the revolutions were discounted
20 per cent., supposing the engines and propellers to be increased in
size to scale. To provide the requisite enormous boiler power, all
geometrical scale would disappear; but it would carry us too far at
present to follow up this interesting comparison.

Our naval architect is not likely at present to proceed further with
this monstrous design, exceeding even the Great Eastern in size, if
only because no dock is in existence capable of receiving such a ship.
He has however learned something of value, namely, that this vessel,
if the proper similitude is carried out, is capable of keeping up a
speed of 24 knots for five days with ample coal supply, provided the
boilers are not found to occupy all the available space. For it is an
immediate consequence of Froude's laws that in similar vessels run at
corresponding speeds over the same voyage, the coal capacity is
proportionately the same, or that a ton of coal will carry the same
number of tons of displacement over the same distance. Thus our
enlarged City of Paris would require to carry about 4,000 tons of
coal, burning 800 tons a day.

With the Britannic and Germanic as models of 5,000 tons and 5,000
horse power at 16 knot speed, the 24 knot vessel would require to be
of 57,000 tons and 85,000 horse power, to carry sufficient coal for
the voyage of 3,000 miles. These enormous vessels being out of the
question, the designer must reduce the size. But now the City of Paris
will no longer serve as a model, he must look elsewhere for a vessel
of high speed, and smaller scale, and naturally he picks out a torpedo
boat at the other end of the scale. A speed of 24 knots - and it is
claimed even of 25, 26, and 27 knots - has been attained on the mile by
a torpedo boat. But such a performance is useless for our mode of
comparison, as sufficient fuel at this high speed for ten or twelve
hours only at most can be carried - a voyage of, say, 500 miles; while
our steamer is required to carry coal for 3,000 miles. The Russian
torpedo boat Wiborg, for instance, is designed to carry coal for 1,200
miles at 10 knot speed; but at 20 knots this fuel would last only
twenty-seven hours, carrying the vessel 540 miles. It will now be
found that with this limited coal capacity the speed of the ordinary
torpedo boat must be reduced considerably below 10 knots for it to be
able to cross the Atlantic, 3,000 miles under steam. So that, even at
a possible speed of 10 knots for the voyage, the full sized 24 knot
five-day vessel, of which the best torpedo boat is the model, must
have (2.4)^{6}, say 200 times the tonnage, and (2.4)^{7}, or 460 times
the horse power. The enlarged Wiborg would thus not differ much from
the enlarged City of Paris. A better model to select would be one of
the recent dispatch boats, commerce destroyers, or torpedo catchers,
recently designed by Mr. W.H. White, for our navy - the Intrepid or
Endymion, for instance. The Intrepid is 300 ft. by 44 ft., 3,600 tons,
and 9,000 horse power for 20 knot speed, with 800 hours' coal capacity
for 8,000 miles at 10 knot speed; which will reduce to 3,000 miles at
16 knots, and 2,000 miles at 20 knots.

The Endymion is 360 ft. by 60 ft., with coal capacity for 2,800 miles
at 18 knot speed, or for about 144 hours or six days. The enlarged
Endymion for the same voyage of 2,800 miles in five days, or at 21½
knot speed, would be 44 per cent larger and broader, that is 520 ft.
by 86 ft., and of threefold tonnage, and three and a half times, or
about 30,000 horse power - about the dimensions of the Furst Bismarck,
but much more powerfully engined. This agrees fairly with the estimate
in the SCIENTIFIC AMERICAN of 19th Sept, 1891., where it is stated
that twenty-two boilers, at a working pressure of 180 lb. on the
square inch, would be required, allowing 1½ lb. of coal per horse
power hour.

The Intrepid, enlarged to a 24 knot boat, for the same length of
voyage of 3,000 miles, would be 650 ft. by 100 ft., 40,000 tons, and
about 45,000 horse power. So now we are nearing the Messrs. Thomson
design in the Naval Exhibition of the five-day steamer, 23½ knot
speed, 630 ft. by 73 ft., and 30,000 to 40,000 horse power.

No one doubts the ability of our shipbuilding yards to turn out these
monsters; and on the measured mile, and for a good long distance, we
shall certainly see the contract speeds attained and some excelled.
But the whole difficulty turns on the question of the coal capacity,
and whether it is sufficient to last for even five days or for 3,000
miles. Every effort then must be made to shorten the length of the
voyage from port to port; and we may yet see Galway and Halifax, only
2,200 miles apart, once more mentioned as the starting points of the
voyage as of old, in the earliest days of steam navigation. In those
days the question of fuel supply was a difficulty, even at the then
slow speeds, in consequence of the wasteful character of the engines,
burning from 7 lb. of coal and upward per horse power hour. Dr.
Lardner's calculations, based upon the average performance of those
days, justified him in saying that steam navigation could not pay - as
was really the case until the introduction of the compound engine.

It is recorded in Admiral Preble's "Origin and Development of Steam
Navigation," Philadelphia, 1883, page 160, that the Sirius, 700 tons
and 320 horse power, on her return voyage had to burn up all that old
be spared on board, and took seventeen days to reach Falmouth. An
interesting old book to consult now is Atherton's "Tables of Steamship
Capacity," 1854, based as they are upon the performance of the marine
engine of the day. Atherton calculates that a 10,000 ton vessel could
at 20 knots carry only 204 tons of cargo 1,676 miles, while a 5,000
ton vessel at 18 knots on a voyage of 3,000 miles could carry no cargo
at all. Also that the cost per ton of cargo at 16 knots would be
twenty times the cost at eight knots, implying a coal consumption
reaching to 12 lb. per horse power hour. It is quite possible that
some invention is still latent which will enable us to go considerably
below the present average consumption of 2 lb. to 1½ lb. per horse
power hour; but at present our rate of progress appears asymptotic to
a definite limit.

To conclude, the whole difficulty is one of fuel supply, and it is
useless to employ a fast torpedo boat as our model, except at the
speed at which the torpedo boat can carry her own fuel to cross the
Atlantic. If the voyage must be reduced in time, let it be reduced
from six days to four, by running between Galway and Halifax, a
problem not too extravagant in its demands for modern engineering
capabilities. A statement has recently gained a certain amount of
circulation to the effect that the Inman Company was about to use
petroleum as fuel, in order to obtain more steam. We have the best
possible authority for saying there is not the least syllable of truth
in this rumor. It has also been stated that since solid piston valves
have been fitted to the Teutonic in lieu of the original spring ring
valves, she has steamed faster. This rumor is only partially true. Her


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Online LibraryVariousScientific American Supplement, No. 841, February 13, 1892 → online text (page 6 of 11)