a short time in showing the first steps of the locomotive; the more so,
as I am speaking to those who are so largely engaged in the daily
working of that now beautifully perfect machine. Various and for a time
unsuccessful experiments were made to bring out a machinery or
travelling engine, as it was first called. A patent was taken by a Mr.
Trevethick for a locomotive to run on common roads, and to a certain
extent it did work. An amusing anecdote is told of it. In coming up to a
toll-gate, the gatekeeper, almost frightened out of his seven senses,
opened the gate wide for the monster, as he thought, and on being asked
what was to pay, said "Na-na-na-na!" "What have we got to pay?" was
again asked. "No-noth-nothing to pay, my dear Mr. Devil; do drive on as
fast as you can!" This, one of the first steam carriages, reached London
in safety, and was exhibited in the square where the large station of
the London and North-Western Railway now stands. Sir Humphrey Davy took
great interest in it, and, in writing to a friend, said: "I shall hope
soon to see English roads the haunts of Captain Trevethick's dragons."
The badness of roads, however, prevented its coming into general use.
Trevethick in 1804 constructed a locomotive for the Merthyr and Tydvil
Rail in South Wales, which succeeded in drawing ten tons at five miles
an hour. The boiler was of cast-iron, with a one-cylinder engine, spur
gear and a fly-wheel on one side. He sent the waste steam into the
chimney, and by this means was very nearly arriving at the blast-pipe,
afterwards the great and important discovery of George Stephenson. The
jumping motion on the bad roads, however, caused it constantly to be
dismounted, and it was given up as a practical failure, being sent to
work a large pump at a mine. Trevethick was satisfied with a few
experiments, and then gave it up for what he thought more profitable
speculations, and no further advances were made in locomotives for some
years. An imaginary difficulty seems to have been among the obstacles to
its progress. This was the supposition that if a heavy weight were to be
drawn, the grip or bite of the wheels would not be sufficient, but that
they would turn round and leave the engines stationary, hence Trevethick
made his wheels with cogs, which of course tended to cause great jolts,
as well as being destructive to the cast-iron rails.
A Mr. Blenkinsop of Leeds patented in 1811 a locomotive with a racked or
toothed rail. It was supported on four wheels, but they did not drive
the engine; its two cylinders were connected to one wheel behind, which
was toothed and worked in the cog-rail, and so drove the engine. It
began running on Middleton Coal Rail to Leeds, three and a quarter
miles, on the 12th August 1812, and continued a great curiosity to
strangers for some years. In 1816 the Grand Duke Nicholas of Russia saw
this engine working with great interest and expressions of no slight
admiration. An engine then took thirty coal-waggons at three and a
quarter miles in an hour.
We next come to Messrs. Chapman of Newcastle, who in 1812 tried to
overcome the supposed want of adhesion by a chain fixed at the ends of
the line and wound round a grooved drum driven by the engine. It was
tried on the Heaton Rail near Newcastle, but was found to be so clumsy
that it was soon abandoned. The next was a remarkable contrivance--a
mechanical traveller to go on legs. It never got beyond its experimental
state, and unfortunately blew up, killing several people. All these
plans show how lively an interest was then being taken in endeavouring
to bring out a good working locomotive. Mr. Blackett, however,
persevered hard to perfect a railway system, and to work it by
locomotives. The Wylam waggon-way, one of the oldest in the North, was
made of wooden rails down to 1807, and went to the shipping-place for
coals on the Tyne. Each chaldron-waggon was originally drawn by a horse
with a man in charge, only making two journeys in the one day and three
on the following, the man being allowed sevenpence for each journey.
This primitive railway passed before the cottage where George Stephenson
was born, and was consequently one of the first sights his infant eyes
beheld; and little did his parents think what their child was destined
to work out in his day for the advancement of railways. Mr. Blackett
took up the wood and laid an iron plate-way in 1808, and in 1812 he
ordered an engine on Trevetbick's principle. It was a very awkward one,
had only one cylinder of six inches diameter, with a fly-wheel; the
boiler was cast-iron, and was described by the man who had charge of it
as having lots of pumps, cog-wheels, and plugs. It was placed on a
wooden frame with four wheels, and had a barrel of water on another
carriage to serve as a tender. It was at last got on the road, but
would not move an inch, and her driver says:--"She flew all to pieces,
and it was the biggest wonder we were not all blown up." Mr. Blackett
persevered, and had another engine, which did its work much better,
though it often broke down, till at length the workmen declared it a
perfect plague. A good story is told of this engine by a traveller, who,
not knowing of its existence, said, after an encounter with the
Newcastle monster working its great piston, like a huge arm, up and
down, and throwing out smoke and fire, that he had just "encountered a
terrible deevil on the Hight Street road."
We now come to George Stephenson, who did for the locomotive what Watt
did for our other steam-engines. His first engine had two vertical
cylinders of eight inches diameter and two-feet stroke, working by
cross-heads; the power was given off by spur-wheels; it had no springs,
consequently it jolted very much on the then bad railways; the wheels
were all smooth, as Stephenson was sure the adhesion would be
sufficient. It began work on the 25th July 1814, went up a gradient of
one in 450, and took eight waggons with 30 tons at four miles an hour.
It was by far the most successful engine that had yet been made. The
next and most valuable improvement of Stephenson was the blast-pipe--by
its means the slow combustion of the fire was at once overcome, and
steam obtained to any amount. This pipe was the result of careful
observation and great thought. His next engine had horizontal connecting
rods, and was the type of the present perfect machine. This truly great
man did not rest here, but time would fail, as well as your patience, if
I were to proceed further. Enough to say, that he afterwards established
a manufactory at Newcastle, and time has shown the result and benefit it
has proved to the whole world at large. A short time before the
Liverpool and Manchester Railway was opened, Stephenson was laughed at
because he said he thought he could go thirty miles an hour, and was
urged before the House of Commons not to say so, as he might be thought
to be mad. This I have from person who knew the circumstances.
Nevertheless, at the trial, I believe the "Rocket" did go at the rate of
thirty miles an hour, to the not small astonishment of the world, and
especially to the unbelievers in steam as a land agent. The stipulation
made was that trains were to be conveyed at the rate of twelve miles an
hour.
In our present perfect engines, the coke or fuel consumed per mile is
about 18 lbs. with a train of 100 tons gross weight, carrying 250
passengers. A first-class carriage weighs 6 tons 10 cwts.; a
second-class, 5 tons 10 cwts., each with passengers; a Pullman car
weighs about 30 tons. Our steamers consume 5 lbs. of coal per
horse-power in one hour. And last, not least, one of the greatest
improvements we have had in steam propulsion is the screw. Again, I may
also name the great advantage derived from steam by our farmers in
thrashing out grain. The engines principally used in farm-work are what
are termed high-pressure, or of the same class as the locomotive. The
great saving in cost in the first place, the simplicity and ease of
action in the second, and the small quantity of water required to keep
them in action, are all reasons why they should be preferred. The danger
in the one, that is, the high-pressure, over the condenser, is very
small, and all that is required is common care to guard against
accidents. Steam being a steady power, is much to be preferred to
water, as by its constant and uniform action the tear and wear of
machinery is much diminished, and of course proportionate saving made in
keeping up the mill or any other machinery.
Having now, to the best of my power, so far as a single lecture will
permit, brought the steam-engine from 120 B.C. to the present time, it
only remains for me to say, that it shows how actively the mind of man
has been permitted to work to bring it to perfection by the direction of
an all-wise Providence, "who knows our necessities before we ask, and
our ignorance in asking." A traveller by rail sees but little of the
vast and difficult character of the works over which he is carried with
such ease and comfort. Time is his great object. No age of the world has
conquered such difficulties as our engineers have had to deal with, and
the result is now before the eye of every thinking traveller. Our
engineers were at first self-taught, and many a self-taught man has had
reason to rejoice in the time he spent in his education. Of these men we
have examples in Brindley, who was at first a labourer and afterwards a
millwright; Telford was a stone-mason; Rennie a farmer's son apprenticed
to a millwright; and George Stephenson was a brakesman at a colliery.
Perseverance with genius, and a determination to overcome, made them the
great men they were. That you may so persevere and strive is the earnest
wish of him who has this evening had the great pleasure of giving you
this lecture, and who feels so greatly obliged to you for the very
patient hearing you have given him.
_ON ATTRACTION_.[B]
_Gravitation_.--Attraction, which may be illustrated by the effect a
magnet has on a piece of iron, may be viewed generally as an influence
which two bodies, say, exert on each other, under which, though at a
distance, they tend to move towards each other till they come into
contact. The force by which a body has weight, and, when free, falls to
the ground, is of this nature; and it is called, from _gravis_, "heavy,"
the gravitating force of the earth, because it causes weight, and
because, though emanating in a small degree from the falling body, it is
mainly exerted by the earth itself. It is under the action of gravity
that a pendulum oscillates: it is by that unseen influence it begins to
sway alternately downward and upward as soon as it is moved to a side;
and it is only because it is withheld by the rod that the ball or bob
keeps traversing the arc of a circle and does not fall straight to the
earth.
All material substances, however small, and however light, buoyant, and
ethereal they may seem, are subject to this force: the tiniest speck in
a sunbeam and the most volatile vapour, equally with the heaviest metal
and the hugest block, the particles of bodies as well as the bodies
themselves. The rising of a balloon in the air may seem an exception to
this law; but it is not so; for the balloon rises, not because the
particles of the gas with which it is inflated are not acted upon by the
earth's attraction, but because the air outside being bulk for bulk
heavier than the air inside, its particles press in below the balloon
and buoy it up, until it reaches a stratum of the atmosphere where, the
pressure being less, the air outside is no heavier than the air
within--a fact which rather proves than disproves the universal action
of gravitation; because the greater weight of the air in the lower
strata of the atmosphere is due to the pressure of the air in those
above, and the balloon ceases to ascend because it has reached a point
where the air outside is the same weight as the air within, and the
weight in both cases is caused by the attraction of the earth.
And not only is the force of attraction universal, it is the same for
every particle; for though this may seem to be contradicted by the fact
that some bodies fall faster to the ground than others, that fact is
fully accounted for by the greater resistance which the air offers to
the falling of lighter bodies than to the falling of heavier. A
particles of bodies, and all bodies, tend to fall with the same
velocity, and, in fact, all do; for though, for the reason just stated,
a feather will take longer to reach the ground than an ounce of lead, an
ounce of lead will fall as fast as a hundredweight. And that it is the
resistance of the air, and not any diminution in the power of
attraction, which causes the feather to lag behind, may be proved by
experiment; for if you let a feather and a coin drop together from the
top of the exhausted receiver of an air-pump, they will both be seen to
descend at the same rate, and reach the bottom at the same instant; a
fact which may be demonstrated more simply by placing the coin and
feather free of each other in a paper cone, and letting the cone fall
with its apex downwards, so as to break the air's resistance; or by
suspending a piece of gold-leaf in a bottle, and letting the bottle
drop--of course short of the ground--in which case the included leaf
will be seen to have gone as fast and as far as the bottle.
It is to be especially noticed that attraction is no lopsided affair;
that it is mutual; that, while the larger body attracts the less, the
less also attracts and moves the larger in proportion; and that, indeed,
every body and every particle attracts every other, far as well as near,
to the utmost verge of the universe of matter. Under it the moon
maintains its place with reference to the earth, the planets with
reference to the sun, and the solar system with reference to the
stellar. As for the moon, it maintains its orbit and revolves round the
earth under the action of two forces, the one akin to that by which a
ball is projected from the mouth of a cannon, and the other the
attraction of the earth, which, by its constant and equal operation,
bends its otherwise rectilineal track into a circular one, as we might
show if we could only project a ball with such a force as exactly to
balance the power of gravity, so that it would at no point in its course
be drawn nearer the earth than at starting.
That the force we are considering pervades the solar system is
demonstrable, for it is on the supposition of it and the laws it is
known to obey that all the calculations of astronomy--and they never
miscarry--are grounded; and it is by noticing disturbances in the
otherwise regular movements of certain planets that astronomers have
been led more than once to infer and discover the presence of some
hitherto unknown body in the neighbourhood. It was actually thus the
planet Neptune was discovered in 1846. Certain irregularities had been
observed in the movements of Uranus, which could not be accounted for by
the influence of any other bodies known to be near it; and these
irregularities, being carefully watched and studied, gradually led more
than one astronomer first to the whereabouts, and then to the vision of
the disturbing planet.
Notwithstanding what we said about the universality of this force, and
how it affects all forms of matter, it may still appear as if the air
were an exception. But it is not so; the air also gravitates. The fact
that it gravitates is proved in various ways. First, if it did not, it
would not accompany the earth in its movements round the sun; the earth
would sweep along into space, and leave it behind it. Secondly, if we
place a bottle from which the air is exhausted in a balance and exactly
poise it with a counter-weight, and then open it and let in the air, it
will show at once that the air has weight or gravitates by immediately
descending. Thirdly, if we extend a piece of india-rubber over the end
of a vessel and begin to withdraw the air from it, we shall see the
india-rubber sink in, under the pressure of the air outside, to fill up
the space left vacant by the removal of the included air. The fact that
air gravitates we have already taken for granted in explaining the
ascent of a balloon; and the proofs now given are enough to show that
the cause assumed is a real one. The lighter gas rises and the heavier
sinks by law of gravitation.
_Gravitation and Cohesion._--Unlike the attraction of aggregation, or
cohesion, which acts only between particles separated from each other
by spaces that are imperceptible, gravitation takes effect at distances
which transcend conception, but it diminishes in force as the distance
increases. The law according to which it does so is expressed thus; its
intensity decreases with the square of the distance; that is to say, at
twice the original distance it is 1-4th; at thrice, 1-9th; at four
times, 1-16th, for 4, 9, 16 are the squares respectively of 2, 3, and 4.
To take an instance, a ball which weighs 144 lb. at the surface of the
earth will weigh 1-4th of that, or 36 lb., when it is twice as far from
the centre as it is at the surface; and 1-9th, or 16 lb. when it is
thrice as far; and 1-16th, or 9 lb. when it is four times as far. The
attraction of cohesion, on the other hand, as we say, acts only when the
particles seem almost in contact, and it ceases altogether when once, by
mechanical or other means, the bond is broken, in consequence of the
particles being forced too near, or sundered too far from, one another.
One distinguishing difference between the attraction of gravitation and
that of cohesion is, that whereas the former is uniform, the latter is
variable; that is, under gravitation the attraction of any one particle
to any other is the same, but under cohesion, some sets of particles
are more forcibly drawn together than others. For instance, a particle
of iron and a particle of cork gravitate equally, but particles of iron
and particles of cork among themselves do not cohere equally. And it is
just because those of the former cohere more than those of the latter,
that a piece of iron feels harder and weighs heavier than a piece of
cork.
Further, the attraction of gravitation is unaffected by change in the
condition of bodies, while that of cohesion is. It makes nothing to
gravitation whether a piece of metal is as cold as ice, or heated with a
sevenfold heat. Not so to the power of cohesion; withdraw heat, and the
particles under cohesion cling closer; add it, and both the spaces grow
wider and the attraction feebler. Thus, for example, you may suspend a
weight by a piece of copper-wire, and the wire not break. But apply heat
to the wire, and its cohesion will be lessened; the force of gravitation
will overpower it, rupture the wire, and cause the weight to fall.
_Cohesion_.--That the action of the attraction of cohesion depends on
the contiguity of the particles in the cohering body, may be shown by
an illustration. Take a ball of lead, divide it into two hemispheres,
smooth the surfaces of section, then press them together, and you will
find it requires some force to separate them; thus proving the
dependence of cohesion on contiguity, although the effect in this case
may be due in some degree to the pressure of the atmosphere as well as
the power of cohesion.
Heat is the principal agent in inducing cohesion, as well as in relaxing
its energy; for by means of it you can weld the hardest as well as the
softest substances into one, and two pieces of iron together, no less
than two pieces of wax. It is possible, indeed, by heat to unite two
sufficient waxed corks to one another, so as to be able by means of the
one to draw the other out of a bottle: such, in this case, is the force
of cohesion induced by heat.
The power of cohesion exists between the particles of liquids as well as
those of solids, the only difference being that in solids the particles
are relatively fixed, while in liquids they move freely about one
another, unless indeed when they are attracted to the surface of a
solid--a fact we are familiar with when we dip our finger into a vessel
of water. The cohesive power of liquids is overcome by heat as well as
that of solids, only to a much greater degree, for under it they assume
a new form, acquire new properties, and expand immensely in volume. They
pass into the form of vapour, occupy a thousand times larger area, and
possess an elasticity of compressibility and expansibility they were
destitute of before.
There is a beautiful phenomenon which accompanies the expansion of ether
under the influence of heat. Placed in a flask to which heat is applied,
the ether will go off in vapour; and as the heat increases, the vapour
will gradually light up into a lovely flame. The expansibility of air,
which is vapour in a permanent form, can be shown by experiment. If we
tie up an empty or collapsed bladder, and place it in a vessel over an
air-pump, we may see, as we withdraw the air from the vessel, and so
diminish its pressure, the bladder gradually expand and swell as it does
under inflation.
The cohesive power of water is beautifully illustrated. Have a small
barrel or bucket so constructed as to be fitted with gauze at the top;
immerse it exactly, so that the water may form a film between the
meshes, and then open the tap at the bottom: the water will not flow
till the meshes at the top are broken by blowing on their surface. The
adhesion of the particles in a soap-bubble is another illustration, no
less beautiful, as well as more familiar; for the soap, which might be
supposed to be the cause of the phenomenon, serves only to prevent the
intrusion of dust between the particles, but by no means to intensify
their attractive power.
There are some liquids the adhesiveness of whose particles is so perfect
as to bar out the access of air when we strew them on the surface of
other liquids; and on the Continent it is not uncommon to protect wines
against the action of the atmosphere by, instead of corking the bottle,
simply pouring in a few drops of oil, which, being lighter than the
wine, floats on the surface. It is parallel to the instance of the
barrel with the gauze-wire top mentioned above, that if we loosely plug
a bottle full of liquid with a piece of cotton-wool, and invert it, the
particles in contact with the wool will cohere so closely that the fluid
will not be able to escape. The adhesiveness of the particles of water
to a solid surface can be exemplified by allowing one of the scales of a
balance to float in water and leaving the other free; the one in
contact with the water will refuse to yield after we have placed even a
tolerable weight in the other which is suspended in the air.
The power of cohesion is more rigorous in some bodies than others. In
some cases the body will rupture if it is interfered with ever so
little; in others, the particles admit of a certain displacement, and if
the limits are not transgressed, they return to their original position
when the compressing or distending cause is removed. This rallying power
in the cohesive force is called Elasticity, and it exists in no small
degree in glass. The spaces between the particles can, within limits, be
either lessened by compression or increased by distension, and the
particles retain their power of recovering and maintaining the relation
they stood in before they were disturbed. It is the power of cohesion or
aggregation which resists any disturbance among the particles, and which
restores order among them when once disturbance has taken place. And not
only does nature resist directly any undue interference with the
cohering force, but tampering with it even slightly has often a certain
deteriorating effect upon the physical properties of bodies. A bell,
for instance, loses its tone when heated, because by that means its
particles are disturbed; though it recovers its tone-power as it cools,
and as the particles return to their places.
In organic bodies, both during growth and decay, the particles are more
or less in flux; but in feathers, after their formation, the attraction
of aggregation remains constant, and by means of it their particles
continue fixed in their places, not only with the life of the bird, but
long after. Nay, you may even crumple them up, and toss them away as
worthless, and yet if you expose them to the vapour of steam, they will
not only recover their form, but they can be made to look as beautiful
as ever.