Lectures on Popular and Scientific Subjects by John Sutherland Sinclair, Earl of Caithness

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LECTURES

ON

POPULAR AND SCIENTIFIC SUBJECTS

BY THE

EARL OF CAITHNESS, F.R.S.

_DELIVERED AT VARIOUS TIMES AND PLACES._

Second Enlarged Edition.

LONDON:
TRUeBNER & CO., LUDGATE HILL.
1879.

Ballantyne Press

BALLANTYNE, HANSON AND CO.

EDINBURGH AND LONDON

CONTENTS.

COAL AND COAL MINES

SCIENCE APPLIED TO ART

A PENNY'S WORTH; OR, "TAKE CARE OF THE PENCE, AND
THE POUNDS WILL TAKE CARE OF THEMSELVES"

PAST AND PRESENT MEANS OF COMMUNICATION

THE STEAM-ENGINE

ON ATTRACTION

THE OIL FROM LINSEED

HODGE-PODGE; OR, WHAT'S INTILT

LECTURES ON POPULAR AND SCIENTIFIC SUBJECTS.

_COAL AND COAL-MINES._

There are few subjects of more importance, and few less known or thought
about, than our coal-mines. Coal is one of our greatest blessings, and
certainly one originating cause of England's greatness and wealth. It
has given us a power over other nations, and vast sums of money are
yearly brought to our country from abroad in exchange for the coal we
send. Nearly L17,000,000 is the representative value of the coal raised
every year at the pit's mouth, and L20,000,000 represent its mean value
at the various places of consumption. The capital invested in our
coal-mining trade, apart from the value of the mines themselves,
exceeds L20,000,000 sterling, and the amount of coal annually extracted
from the earth is over 70,000,000 of tons. Taking the calculation of a
working miner--J. Ellwood, Moss Pit, near Whitehaven--we may state, that
if 68,000,000 tons were excavated from a mining gallery 6 feet high and
12 feet wide, that gallery would be not less than 5128 miles, 1090
yards, in length; or, if this amount of coal were erected in a pyramid,
its square base would extend over 40 acres, and the height would be 3356
feet.

There are grounds for believing that the produce of the various
coal-fields of the world does not at present much exceed 100,000,000 of
tons annually, and therefore our own country contributes more than
three-fifths of the total amount. If we divide the coal-yielding
counties of Britain into four classes, so as to make nearly equal
amounts of produce, we find that Durham and Northumberland yield rather
more every year than seven other counties, including Yorkshire.
Derbyshire, again, produces more than eight other counties, and nearly
as much as the whole of North and South Wales, Scotland, and
Ireland--the yield of the latter being about 17,000,000 of tons, and
that of the two first-named about 16,000,000 of tons.

In 1773 there were only 13 collieries on the Tyne, and these had
increased to upwards of 30 in 1800. The number of collieries in 1828 had
increased to 41 on the Tyne, and 18 on the Wear, in all 59, producing
5,887,552 tons of coal. The out-put of coal in Northumberland and Durham
in 1854 was no less than 15,420,615 tons, and now in these two counties
there are 283 collieries. Mining began on the Tyne and continued on the
Wear, where the industry has been largely developed. There are in all
about 57 different seams in the Great Northern coal-field, varying in
thickness from 1 inch to 5 feet 5 inches and 6 feet, and these seams
comprise an aggregate of nearly 76 feet of coal. Taking the area of this
field to be 750 square miles--a most probable estimate--we may classify
the contents as household coal, steam coal, or those employed in
steam-engine boilers, and coking coal, employed for making coke and gas.
Of household coal there is only 96 square miles out of the total 750,
all the remainder being steam or coking and gas coal. The greater part
even of this 96 square miles has been worked out on the Tyne, and the
supply is rapidly decreasing also on the Wear, where the largest bulk
of the household coal lies. The collieries of the Tees possess but six
square miles out of the 96, as far as we at present know. Turning,
however, to that part of the coal-field regarded as precarious, and
consisting of first, second, and third-rate household coal, we have for
future use 300 square miles. London was formerly supplied from the pits
east of Tyne Bridge, where is the famous Wallsend Colliery, which gave
the name to the best coal. That mine is now drowned out, and, like the
great Roman Wall, at the termination of which it was sunk, and from
which it derived its name, is now an antiquity. There is now no Wallsend
coal, and the principal part of the present so-called coal comes from
the Wear, but the seam which supplied that famous pit is continued into
Durham, and that seam, or its equivalent, sends a million or two of tons
every year into London. The supply, however, in this district is rapidly
decreasing. Careful calculations have been made as to the probable
duration of this coal, of which the following is a summary. The workable
quantity of coal remaining in the ten principal seams of this coal-field
is estimated at 1,876,848,756 Newcastle chaldrons (each 35 cwt.).
Deducting losses and underground and surface waste, the total
merchantable round or good-sized coal will be 1,251,232,507 Newcastle
chaldrons. Proceeding on this estimate, formed by Mr. Grunwith in 1846,
we may arrive at the probable duration of the supplies: taking the
future annual average of coal raised from these seams to be 10,000,000
of tons--and this is under the present rate--the whole will be exhausted
in 331 years. A still later estimate was made by Mr. T.G. Hall in 1854,
and he reckoned the quantity of coal left for future use at
5,121,888,956 tons; dividing this by 14,000,000 of tons as the annual
consumption, the result would be 365 years; and should the annual demand
arrive at 20,000,000 of tons, the future supply of this famous
coal-field would continue for 256 years. The total available coal (1871)
in the British coal-fields, at depths not exceeding 4000 feet, and in
seams not less than 1 foot thick, is 90,207,285,398 tons, and taking
into account seams which may yet become available, lying under the
Permian, New Red Sandstone, and other superincumbent strata, this
estimate is increased to 146,480,000,000 of tons. This quantity, at the
present annual rate of production throughout the country--namely,
123,500,000 tons--would last 1186 years. Other estimates of various
kinds relative to our coal supply have been put forth: some have
asserted that, owing to increasing population and increasing consumption
in manufactures, it will be exhausted in 100 years, and between this
extreme and that of 1186 years there are many other conjectures and
estimates.

In the United States there are about 120,000 square miles underlaid by
known workable coal-beds, besides what yet remains to be discovered;
while on the cliffs of Nova Scotia the coal-seams can be seen one over
the other for many hundred feet, and showing how the coal was originally
formed. With this immense stock of fuel in the cellars of the earth, it
seems evident that we need not trouble our minds or be anxious as to the
duration of our coal supply. Besides, the conversion of vegetable matter
into coal seems to be going on even now. In the United States there are
peat-bogs of considerable extent, in which a substance exactly
resembling cannel coal has been found; and in some of the Irish
peat-beds, as also in the North of Scotland, a similar substance has
been discovered, of a very inflammable nature, resembling coal.

Yes! what could have produced this singular-looking, black, inflammable
rock? How many times was this question asked before Science could return
an answer? This she can now do with confidence. Coal was once growing
vegetable matter. On the surface of the shale, immediately above the
coal, you will find innumerable impressions of leaves and branches, as
perfect as artist ever drew. But how could this vegetable matter ever
accumulate in such masses as to make beds of coal of such vast extent,
some not less than 30 feet thick? It would take 10 or 12 feet of green
vegetable matter to make 1 foot of solid coal. Let us transport
ourselves to the carboniferous times, and see the condition of the
earth, and this may assist us to answer the question. Stand on this
rocky eminence and behold that sea of verdure, whose gigantic waves roll
in the greenest of billows to the verge of the horizon--that is a
carboniferous forest. Mark that steamy cloud floating over it, an
indication of the great evaporation constantly proceeding. The scent of
the morning air is like that of a greenhouse; and well it may be, for
the land of the globe is a mighty hothouse--the crust of the earth is
still thin, and its internal heat makes a tropical climate everywhere,
unchecked by winter's cold, thus forcing plants to a most luxurious
growth.

Descend, and let us wander through this forest and examine it more
closely. What strange trees are here! No oaks, no elms, or ash, or
chestnut--no trees that we ever saw before. It looks as if the plants of
a boggy meadow had shot up in a single night to a height of 60 or 70
feet, and we were walking among the stalks--a gigantic meadow of ferns,
reeds, grasses, and club-mosses. A million columns rise, so thick at the
top that they make twilight at mid-day, and their trunks are so close
together we can scarcely edge our way between them, whilst the ground is
carpeted with trailing plants completely interwoven. What strange trees
they are! Beneath us lies an accumulation of vegetable matter more than
200 feet in thickness--the result of the growth and decay of plants in
this swamp for centuries. All things are here favourable for the growth
of vegetation--the great heat of the ground causes water to rise rapidly
in vapour, and this again descends in showers, supplying the plants with
moisture continuously. The air contains a large proportion of carbonic
acid gas, poison to animals but food to plants, which, by means of its
aid, build up their woody structure. Winds at times level these gigantic
plants, for their hold on the earth is feeble, and thus the mass goes on
increasing.

We are now on the edge of a lake abounding with fish, whose bony scales
glitter in the water as they pursue their prey. Lying along the shore
are shells cast up by the waves, and there are also seen the tracks of
some large animals. How like the impression of a man's hand some of
these tracks are! The hind-feet are evidently much larger than the
fore-feet. There is the frog-like animal which made them, and what a
size! It must be six feet long, and its head looks like that of a
crocodile, for its jaws are furnished with formidable rows of long,
strong, sharp, conical teeth.

The continued growth and decomposition of the vegetation during long
ages must have produced beds like the peat-deposits of America and Great
Britain. In the Dismal Swamp of Virginia there is said to be a mass of
vegetable matter 40 feet in thickness, and on the banks of the Shannon
in Ireland is a peat-bog 3 miles broad and 50 feet deep. When conditions
were so much more favourable for these deposits, beds 400 feet in
thickness may easily have been produced. This accumulated mass of
vegetable matter must be buried, however, before we can have a coal-bed.
How was this accomplished? The very weight of it may have caused the
crust of the earth to sink, forming a basin into which rivers, sweeping
down from the surrounding higher country, and carrying down mud in their
waters, the weight of which, deposited upon the vegetable matter,
pressed and squeezed it into half its original compass. Sand carried
down subsequently in a similar manner, and deposited upon the mud,
pressed it into shale, and the vegetable matter, still more reduced in
volume by this additional pressure, is prepared for its final conversion
into shale. In time the basin becomes shallow from the decomposition of
sediment on its bottom, and then we have another marsh with its myriad
plants; another accumulation of vegetable matter takes place, which by
similar processes is also buried. Where thirty or forty seams of coal
have been found one below another, we have evidence of land and water
thus changing places many times.

When vegetable matter is excluded from air and under great pressure, it
decomposes slowly, parting with carbonic acid gas; and is first changed
into lignite or brown coal, and then into bituminous coal, or the soft
coal that burns with smoke and flame. I have been in a coal-mine where
the carbonic acid gas, pouring from a crevice in the coal, put out a
lighted candle. The high temperature to which the coal has been
subjected when buried at great depths has also probably assisted in
producing this change; and where that temperature has been very high,
the coal by the influence of the heat having parted with its inflammable
gases, we have the hard or anthracite coal, which burns with little or
no flame and without smoke. It is indeed coal made into coke under
tremendous pressure, and this is the kind of coal which Americans use
exclusively in their dwelling-houses and monster hotels.

It was at first supposed that the plants of the carboniferous times were
bamboos, palms, and gigantic cactuses, such as are now found in tropical
regions, but a more careful examination of them shows that, with the
exception of the tree-fern now found in the tropics, they differ from
all existing trees. A large proportion of the plants of the
coal-measures were ferns, some authorities say one-half. From their
great abundance we may infer the great heat and moisture of the
atmosphere at the time when they grew, as similar ferns at the present
day are only found in the greatest abundance on small tropical islands
where the temperature is high. Coal often contains impressions of fern
leaves and palm-like ferns--no less than 934 kinds are drawn and
described by geologists. Many animals and insects are found in the coal,
such as large toad-like reptiles with beautiful teeth, small lizards,
water lizards, great fish with tremendous jaws, many insects of the
grasshopper tribe, but none of these are of the same species as those
found now living on this globe.

Wood, peat, brown coal, jet, and true coal, are chemically alike,
differing only in their amount of oxygen, due to the difference of
compression to which they were subjected. The sun gave his heat and
light to the forests now turned into coal, and when we burn it ages
afterwards, we revive some of the heat and light so long untouched.
Stephenson once remarked to Sir Robert Peel, as they stood watching a
passing train: "There goes _the sunshine of former ages_!"

COST OF WORKING.

Having thus stated shortly the origin and extent of the coal of this
country, more particularly that of the northern coal-fields of
Northumberland and Durham, I think it may be interesting to say
something of the cost at which this valuable article is obtained, as I
am sure few are at all aware of the vast sums of money that have to be
expended before we can sit down by our comfortable firesides, with a
cold winter night outside, and read our book, or have our family
gathered round us; and few know the danger and hardship of the bold
worker who risks his life to procure the coal. The first step is to find
out if there is coal. This done, the next is to get at it, or, as it is
termed, to _win_ the coal. The process is to sink a shaft, and this is
alike dangerous, uncertain, and very costly. The first attempt to sink a
pit at Haswell in Durham was abandoned after an outlay of L60,000. The
sinkers had to pass through sand, under the magnesian limestone, where
vast quantities of water lay stored, and though engines were erected
that pumped out 26,700 tons of water per day, yet the flood remained the
conqueror. This amount seems incredible, but such is the fact. At
another colliery near Gateshead (Goose Colliery), 1000 gallons a minute,
or 6000 tons of water per day, were pumped out, and only 300 tons of
coal were brought up in the same time, and thus the water raised
exceeded the coal twenty times. The most astonishing undertaking in
mining was the Dalton le Dale Pit, nine miles from Durham. On the 1st
June 1840 they pumped out 3285 gallons a minute. Engines were erected
which raised 93,000 gallons a minute from a depth of 90 fathoms or 540
feet, and this was done night and day. The amount expended to reach the
coal in this pit was L300,000. Mr. Hall estimates the capital invested
in the coal trade of the counties of Durham and Northumberland,
including private railways, waggons, and docks for loading ships, at
L13,000,000 sterling.

The great difficulty in working coal, should these upper seams fail, is
not only the increase of cost in sinking further down, but the increased
heat to be worked in. At 2000 feet the mine will increase in heat 28 deg.,
at 4000, 57 deg.; to this must be added the constant temperature of 50 deg. 5',
so that at 2000 feet it would be 78 deg. 5', and at 4000, 107 deg. 5' Fahr. By
actual trial on July 17, 1857, in Duckingfield Pit, the temperature at
2249 feet was 75 deg. 5'. From this it may be conceived in what great heat
the men have to work, and the work is very hard. One may fancy from this
what can be endured, but it would be next to impossible to work in a
greater temperature. I can speak upon this from actual experience, as
when down the Lady Londonderry Pit the temperature was 85 deg., and here the
men worked naked. Another great source of expense and anxiety lies in
keeping up the roof, as, from the excessive pressure, the roof and floor
are always inclined to come together, and props must therefore be used,
and these in some pits cost as much as L1500 a year. To digress for a
moment, an amusing story is told of Grimaldi, the celebrated clown, when
paying a visit to a coal-pit. Having gone some way through the mine, a
sudden noise, arising from the falling of coal from the roof, caused him
to ask the reason of the noise. "Hallo!" exclaimed Grimaldi, greatly
terrified, "what's that?" "Hech!" said his guide, "it's only a wee bit
of coal fallen down--we have that three or four times a day." "Then I'll
thank you to ring for my basket, for I'll stop no longer among the wee
bits of falling coal." This "wee bit" was about three tons' weight. A
large proportion of the sad accidents in coal-mines is caused by these
falls of the roof, which give no warning, but suddenly come down and
crush to death those who happen to be near.

MODE OF WORKING.

The cost of working having thus been given, I wish now to lay before you
an explanation of the method of working and bringing the coal to the
surface. It may not be uninteresting to mention how many men are
employed in this work, as the number is very large. Coal was not
formerly excavated by machinery, but it is so now, and therefore hands
must be had. The number of men employed in the mines of county Durham in
1854 was 28,000; of these, 13,500 were hewers, winning several thousand
tons of coal daily. Of the remainder, 3500 were safety-staff men,
having, besides, 1400 boys belonging to their staff; 2000 were off-hand
men, for bargain work or other duties; 7600 lads and boys, working
under the various designations of "putters," or pushers of coal-tubs,
underground "drivers," "marrows," "half-marrows," and "foals," these
latter terms being local, and significant of age and labour. For
Northumberland must be added 10,536 persons, and Cumberland 3579, making
a total for these three counties of upwards of 42,000 persons labouring
in and round our northern collieries. The average that each hewer will
raise per day is from two to three tons in thin, and three to four tons
in thick seams. The largest quantity raised by any hewer on an average
of the colliers of England is about six tons a day of eight hours. The
mode of working is very laborious, as the majority of seams of coal
being very thin--that is to say, not more than two feet thick--the
worker of necessity is obliged to work in a constrained position, often
lying on his side; and you can fancy the labour of using a pick in such
a position. To get an idea of the position, just place yourself under a
table, and then try to use a pick, and it will give you a pretty clear
idea of the comfortable way in which a great part of our coal is got,
and this also at a temperature of 86 deg. in bad air. The object, of
course, of the worker is to take nothing but coal, as all labour is lost
that is spent in taking any other material away. The man after a time
gets twisted in his form, from being constantly in this constrained
position, and, in fact, to sit upright like other men is at last
painful. Then an amount of danger is always before him, even in the best
regulated and ventilated pits. This danger proceeds from fire-damp, as
one unlucky stroke of the pick may bring forth a stream of carbureted
hydrogen gas, inexplosive of itself, but if mixed with eight times its
bulk of air, more dangerous than gunpowder, and which, if by chance it
comes in contact with the flame of a candle, is sure to explode, and
certain death is the result--not always from the explosion itself, but
from the after-damp or carbonic acid gas which follows it.

Upwards of 1500 lives are yearly lost from these causes, and not less
than 10,000 accidents in the same period show the constant danger that
the miner is exposed to. It would appear that England has more deaths
from mining accidents than foreign countries, as Mr. Mackworth's table
will show:--

Prussia 1.89 per 1000
Belgium 2.8 "
England 4.5 "
Staffordshire 7.3 "

This statement shows that more care is wanted in this last-named county
especially, as I find that the yield of coal in Belgium is half as much
as in England. Long working in the dark, if one may so speak, is a cause
of serious detriment to the sight, and the worker also suffers much from
constantly inhaling the small black dust, which in course of time
affects the lungs, causing what is known as "miner's asthma." Without
going further into the unhealthy nature of the miner's work, it may be
interesting to mention something of the actual process, and having
myself been an eye-witness of it, I will explain it as shortly as I can.
The workers having arrived at the pit-mouth at their proper hours--for
the pit is worked by shifts, and consequently is generally worked day
and night--the first operation is for each to procure his lamp from the
lamp-keeper, receiving it lighted and locked; this is found to be
necessary, as from the small light given by the Davy-lamp the men are
often tempted to open them, and some are even, so foolhardy as to carry
their lamp on their cap and a candle in the hand, and hence a terrible
explosion may take place. A few words on the Davy-lamp, which came into
use about sixty years ago, may not be out of place here. This
safety-lamp of the miner not only shows the presence of gas, but
prevents its explosion. It is constructed of gauze made of iron-wire
one-fortieth to one-sixtieth of an inch in diameter, having 784 openings
to the inch, and the cooling effect of the current passing through the
lamp prevents the gas taking fire. If we pour turpentine over a lighted
safety-lamp, it will show black smoke, but no flame. Provided with his
lamp, the miner takes his place with others in the tub, which conveys
him with great rapidity to the bottom of the shaft. Here landed, he
takes his way to the workings, some of these, in large pits, being two
miles from the bottom of the shaft. To a novice this is not easy, as you
have to walk in a crouching manner most part of the way. Once there, he
begins in earnest, and drives at his pick for eight hours, the monotony
only relieved by his gathering the products into small railway waggons
or tubs to be removed. This is done mostly by boys, but in the larger
mines by ponies of the Shetland and other small breeds. The tubs are
taken to a part of the mine where, if one may so speak, the main line is
reached, and then formed into trains, and taken to the shaft by means of
an endless rope worked by an engine in the pit. In accomplishing all
this work, great care has to be taken that the current of air is not
changed or stopped. This is effected by means of doors placed in various
parts of the mine, so as to stop the current and drive it in the
required direction. These doors are kept by boys, whose duty it is to
open and close them for the passage of the coal tubs. Those boys are
often allowed no light, and sit in a hole cut in the side of the road
near to the doors. Upon their carefulness the safety of the mine in a
great measure depends, as if they neglect to shut the door the current
of air is changed. I have been told that these boys are subject to
accidents no less than the workers, for, sitting in the dark, and often
alone for hours, they are very apt to go to sleep. To ensure being awoke
at the proper time, they frequently lie down on the line of rails under
the rope, so that when the rope is started it may awake them by its
motion, but at times so sound is their sleep, that it has failed to
rouse them in time, and a train of coal waggons has passed over them,
causing in most cases death.

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