The Sun.
London, England, 1845-06-20 00:00:00

THE SUN, LONDON, FRIDAY EVENING .JUNK 20 1845.

RAIL q, A Y COMMITTEES.
(YESTERDAY.)

HOUSE OF LORDS.

seven miles in length. The loss of power, as indicated by the fall
of the barometer, was 69 per cent. downwards, and on a 30 tons
train it was 57 per cent., the mean power being 43 per cent. He
had since applied Mr. Hawkcsley's formula to the experiments, and
had found them almost precisely correct. He had before supposed that
the loss of power was owing to the leakage. On the Dalkey line
the leakage was 200 feet per minute per mile, and the Dalkey
engine exhausted 3,000 teet per minute, on a line of six or seven
miles in length. There would be a point at which the Dalkey
engine would not move a train at all. There were three
circumstances which would tend to impair the velocity
of the train—the leakage, which would increase in pro-
portion to the length of the line; the increased den-
sity which resulted from that increased leakage; and the in-
creased friction which was a consequence of the increased density—
so that the length of the pipe would act as a direct principle to pro-
duce all these three conditions. The velocity of the train was in
the ratio of the power of the engine to the diameter of the tube; it
was the square of the two diameters ; so that just as

the pipe was increased the power of the engine must
be increased, so that the increase of the power of
the engines on the Portsmouth atmospheric line from 120 to 150
horse-power, while they had increased the diameter of the tube,
had obtained nothing for them. He believed that no atmospheric
line would be sufficient to answer the purposes of the public on a
great line. The line would be subject to greater irregularities,
for on a line cf sixty miles, with stations every three miles,

, thirty stationary engines would be required ; while with
12 mile stations on a locomotive line, only 9 engines would be
required, and there would evidently be less liability from 9 engines
than from 30 engines. The consequence would be, that while any
irregularity which occurred on the atmospheric line would be a perms-
nent, or at least a comparatively durable obstacle, that on the locomo-
tive line would be only transient. In addition to this, there was the
advantage for the locomotive line that the power could be increased
in proportion to the weight of the train which the engine had to
convey, while on the atmospheric line the power must be always
stationary. The endeavour to meet the difficulty by more nume-
rous trains would prove a failure, for it is matter of experience
that the public would not be interfered with by such frequent
trains. There was certainly an advantage on the side of
the atmospheric line in saving the weight of the
tender and engine. The weights of these varied from 16 to
25 tons on the narrow gauge. On the broad gauge the
weight of the engine varied from 23 to 33 tons. The engine and
tender which carried the express train to Birmingham weighed 18
tons, and ran at a rate of 40 miles an hour, performing the 112
miles in three hours. In general the weight of the engine and
tender was about cne-third of the whole train. There would be
great traffic on the Epsom line during certain seasons
of the year, and Mr. Stephenson believed that the
atmospheric principle could not satisfy the requirements of the
traffic. With respect to the safety, he believed that the crossing
places would prove seriously dangerous from the liability to colli-
sion. There was a 100 horse-engine to convey the train down the
plane to Euston-square, and for working 14 or 15 trains a day
over one mile of road, and he calculated that the expense was not
increased by the difference of the power to 150-horse power,
and the distance to three miles, as he found that there would be
an expense of 6001. per mile. The cost of the single engine was
1,491/. 15s. 4d, per annum, and assuming Mr. Samuda's estimates
as correct, viz., that a passage of 2,000 trains in the year would
occasion an expense of 331. a mile—putting this to the 9,0001.
per mile which had been allowed for other purposes, there was a
cost of 1,050/. a mile for working expenses alone. On the
South-Western line the cost was 500/. per mile, allowing
100/. for interest. This was the expense of a single line, for a
double line had not been calculated. With respect to the asser-
tion that the force of gravity alone would carry the trains down
the inclined planes, he had to say that from his own experience he
knew that trains had been stopped by the atmosphere.
To the inquiry of Mr. M. MILNES, Mr. Stephenson replied that
the resistance of the atmosphere was as the square of the surface to
the weight.
To the cross-examination of Mr. TALBOT, Mr. Stephenson re-
plied that he had heard that the line at Dalkey was under ♦ery
unfavourable circumstances. At Dalkey there was a connecting
pipe running at right angles with the main pipe, the leakage in
which was 219 feet in a minute, while that in the vacuum tube
was only 126 feet. But this excess was, in his opinion, attribut-
able as much, or more, to the pump than to the connecting pipe.
The pump was working very efficiently when he was at Dalkey, but
the connecting pipe need not be more than a very short length. He
had stated all this to the Croydon Committee a year ago, and had been
made the subject of their investigation. He had then stated that

the velocity of the train on the Dalkey line was at its maximum,
but it appeared to him that the velocity was accumulating at the
moment the train left the tube. There certainly was a slight accele.
ration, and that he attributed to the diminished friction which had
been laid down in Mr. Hawkesley's formula, and the decrease of
density as the train approached the engine. Last year he had
attributed the whole of the loss of power to leakage, but at that
time he knew nothing of friction. The only difference be-
tween his evidence then and now was, that the loss of velocity
was to be attributed to two elements instead of one. He could
not say whether the result of friction was to be ascribed to the ex-
haustion of the air by the pumping engine, or whether it was the
effect of the impulse of the piston in the tube. The motion of
the train was partly the effect of propulsion and partly the effect
of suction. The rapidity of the motion of the air, at the first stroke
of the pump, was equal to the force of the stroke. But this would
act only on the first column of air which the pump commanded,
but the next column would not move at all, except to an attenuation
allowed by the vacancy left by the air drawn out. The leakage in
the tube and tenacity of the air would be indicated by the height
at which the barometer stood respectively at the engine and on the
piston, but only by a single ratio. Indeed, he could not see the use
of two barometers at all, but if one only were used, the depressing
condition of the mercury in the barometer would indicate the
weight of the air in the tube, and consequently its density. The
atmospheric engine was certainly nut so efficient a machine for trac.
tion as the locomotive. On a small railway of sor 6 miles in length,
with a large traffic,the atmosphericprinciple allowed of an economical
increase in the number of trains. He had stated that the locomo-
tive trains had been obliged to bend to public convenience, but he
could not say that the public had ever been obliged to bend to the
trains. It was, however, true that the London and Birmingham
Company had advertised that the express trains would consist only
of a limited number of carriages. He dared to say that it would
be a convenience if third-class carriages could be taken by the ex-

press trains as well as the first-class carriages. There was a diffi-
culty in dealing with a large number of passengers on particular
occasions, and he would not wish to start quick locomotive trains
oftener than a quarter of an hour from each other, but he thought
the atmospheric trains would be equally dangerous. In the event of
two trains arriving at the same time, and to overrun, and not to
bring up at the stopping places, there would be a danger of collision,
and whether the points were down or up he did not see that the
danger would prevented. This would only happen at the crossings.
He had not estimated the number of crossings, but he believed
that every section of pipe would be a meeting-place. He was,
however, assuming the experience on a locomotive line
and applying it to the atmospheric line; and on a
double line, upon the locomotive principle, there was
a great immunity, but if the man at the junction who had com-
mand of the points turned them the wrong way the collision would
arise. But there was no possibility of a train intended for one line
being put upon another at an ordinary crossing-place, for, in order
to get from one line to the other, the engine would have to be re-
versed. On steep gradients the atmospheric principle had the ad.
vantage, as on a locomotive line the engine would slip the moment
its weight became its load. They assumed the engine at 18 tons
and the carriages at 35, so that the tractive power exerted was
equal to 40 tons, but that had merely reference to expenditure
of fuel, economy in fuel, and velocity, An engine such
as this would take a train up a plane of 1 in 330 at forty miles an
hour. The gradient of 1 in 100 is equal to about 52 feet in a
mile, and an engine of this power would barely take itself up at
that speed. The advantages of the atmospheric principle lay in
overcoming steep gradients, and it would, of course, overcome easier
gradients better; but, on a long line, he thought that it was not
only commercially disadvantageous, but mechanically undesirable.
Locomotive engines could work up gradients of 1 in 100, but at a
very reduced speed.

To Mr. M. MILNES, Mr. Stephenson stated that he had con-
templated a combination of the locomotive and atmospheric prin-
ciples on the line which he had charge of from Tring to Worcester,
where, going up to Dudley, there would be a gradient of 1 in 80
over about five miles of road; but he had found it very expensive.
He had taken his estimates of cost from Mr. Cubitt's evidence, and
coincided with him in the opinion that 67,0001. would be sufficient
for the stationary engines. But in the estimate for the vacuum
tube he differed, as he thought that it ought to be 4,800/.
instead of 4,5001. He based a calculation of 5001. per mile
for water to supply the stationary engines, for they ex-
pended 6,0001. for the engine at Black wall, and 3,000/.
for the wells at Camden-town. He did not, however, know what
facilities there existed for the supply of the water on the proposed
line. The engine at Camden town was constructed by the Messrs.
Maudslay, and worked expansively, but not so much as it might da,
and he could not say whether it was more expansive than the
engine at Dalkey ; but he thought that not a single instance could
be adduced of a stationary engine being worked for so little as
Samuda had stated, and he believed that the extra
expense on the atmospheric line would be above 9,000/.
He was not aware that, exclusive of the electric telegraphic,
the points and crossings and the valve, the two lines were about
equal,but such might be the case. He did not think that it would
be fair to take the number of trains into consideration, because the
weights carried by the locomotive trains were so much greater as to
render them in effect on a par with the greater number of trains
on the atmospheric line.
To the inquiries of Mr. ()swam), Mr. Stephenson stated
that there was no opportunity of judging of the power of
stopping on the Dalkey line, for after the train left the tube
it went up a plane of 1 in 50, so that in feet it was going
up hill, but in his experiments they had failed in obtaining any great
facility in stopping. In starting lie certainly thought the atmos-
pheric principle had something of an advantage.
To the re- examination of Mr. M. SMITH the witness stated that,
in his estimation of working expenses, he had taken the traffic on
both lines as equal. With respect to the opinion expressed by
the promoters of the Dalkey line, he could say that he had fully
considered the reasons alleged, and was quite decided in his
opinions, especially as he was confirmed by the formula of Mr.
Hawkesley and the experiments of Mr. Samuda, which had been
published since his own. The connecting tube at Dalkey
was a solid cast-iron pipe, and was covered with tar, so
that there was every care taken to prevent leakage,
and he believed that a large quantity of the leakage was to be
ascribed to the pump. The same cause would equally operate
whether the pipe were long or short, and the leakage was pretty
uniform throughout the whole length of the line. With respect to
the number of trains, they must of necessity be restricted to the
number of crossing places ; but 12 or 15 trains a day might be
worked with tolerable facility. That, however, depended upon
the equability with which the trains worked, and he thought it
would be practically impossible to secure perfect equability through-
out. The objections to the atmospheric line were chiefly to the
single line, for that was subject to all those overshootings
and collisions of which he had spoken In stating that the
peculiar advantage of the atmospheric principle lay in the power of
overcoming steep gradients, he meant to assert that credit was
due to the rope which drew, as well as to the air which propelled
the train. He had founded his statements on Mr. Samuda's
tables, as well as his own, in fact, on both sets of tables.
Mr. Locke, the eminent engineer, stated that he had paid con-
siderable attention to the atmospheric principle, and had read
most that :had been written on the subject, though he had not
been to Dalkey. He had read Mr. Stephenson's report,
and perfectly agreed with his conclusions, He had
paid attention to the gradients on the direct line, and
in the event of the atmospheric principle proving a failure, it might
be converted into a locomotive line, but it would be a very bad one,
as the gradients on one half of the line varied from 1 in 80 to 1 in
100. The increase of the length of the tube would have the effect
of decreasing the mean velocity, as the leakage would be greater,
and the friction greater, and the via inertia. of the atmosphere
would be more difficult to overcome. The velocity of the motion
of the air in the tube was greater the nearer the engine was ap-
proached, and the further the recession was towards the piston
the less; and the rushing of the air from the neighbour-
hood of the piston towards the other end of the
pipe occasioned a friction of the particles of the air among them-
selves, and thus retarded the piston and, consequently, the train.
He did not think that a single atmospheric line could at all afford
the same accommodation as a double locomotive line. The expense
of the Chichester Railway for a double line, taking the main line
and excluding contingencies, was 17,415/. a mile. On the at-
mospheric single the expense would be 16,650/. a mile ; but if the
latter was a double line, it would cost more than 20,0001 a mile.
The atmospheric tubes would cost 270,000/. ; twenty
engines at 5,0001.-100,0001,—and four crossing en-
gines, 20,0001., and other engines as much more. This
made the whole cost of the way 420,000/. But from this,
there was to 'be deducted the cost of 30 locomotive engines, at
a rate of 1,7501. each, making a total of 52,0001. There was also
20,000/. for sheds and repairing, and 27,0001. for the other charges,
making altogether 100,0001., which, deducted from the gross sum,
gave 320,0001. for the establishment of the atmospheric power.
The interest of this would be 16,000/. a year. Now, the whole
expense for haulage on the Guildford and Chichester line would be
15,7441., so that the whole expense of the latter would
be less than the mere interest for the establishment of

the atmospheric power. With respect to the passage of trains, he
found from experience that there were certain hours of the day
which the public preferred, and at which the trains must necessarily
be large. There was also a great adaptability to the locomotive
principle to supply the sudden and unexpected traffic and to answer
all its variety. He thought that the traffic of the Epsom line would
be as much as that railway could carry, and when the other traffic
came upon it he believed that they would have great difficulty in
meeting it, and at the time of Epsom races, it would be impossible to
convey it, especially when the North Kent traffic came on the
line at Sydenham. With respect to the crossings, he believed the
danger on the atmospheric line would be decidedly greater than on
the locomotive line, particularly as the trains come into the stations
at the top of their speed. They could certainly cut off the tube,
but great precision would be required; and they must either let
off the velocity, or the velocity would involve a certain degree of
danger. With regard to haulage, there were 37 tons of coals
consumed at Dalkey daily, which was equal to 41i horses ;
and applying that to 150 horse power, he found that in-
stead of being 5 7.10 d. it was 7 5.10 d. With respect
to the men at the station he had doubled them, for he was confi.
fident that for the mail trains they would be necessary. The
whole expense of the haulage would by these means be increased
from 74d. to Is. a mile per train. On the Dalkey Railway the
cost of haulage amounts to Is. a mile, where the trains were
lighter than they proposed to have the trains on this line. The
whole expense actually incurred on the Dalkey Railway was
1,4801., and, giving the atmospheric railway every advantage, he
found that the expense of haulage would be Is. a mile. On loco-
motive lines the expenses of haulage was from l Id. to 11 id. per
mile, and in this all the great lines agreed. Taking the estimate
as in tons, the cost would be three times in favour of the locomo.
tive principle, from the greater weight they could carry by one
train.
The Committee here adjourned.