sooner had the girl received the kiss that she knew to be a binding
promise than she dropped her arms, walked off, and shifted the helm.
“Unfasten the sheet here,” she commanded, “and duck your head clear o’
the boom.”
As soon as their faces were set for home, the minister walked back to
the cuddy roof and sat down to reflect. Not a word was spoken till they
reached the harbor’s mouth again, and then he pulled out his watch. It
was half-past four in the morning.
Outside the battery point the girl hauled down the sails and got out
the sweeps; and together they pulled up under the still sleeping town
to the minister’s quay-door. He was clumsy at this work, but she
instructed him in whispers, and they managed to reach the ladder as the
clocks were striking five. The tide was far down by this time, and
she held the boat close to the ladder while he prepared to climb. With
his foot on the first round he turned. She was white as a ghost, and
trembling from top to toe.
“Nance--did you say your name was Nance?”
She nodded.
“What’s the matter?”
“I’ll--I’ll let you off if you want to be let off.”
“I’m not sure that I do,” he said, and stealing softly up the ladder
stood at the top and watched her boat as she steered it back to Ruan.
Three months after they were married, to the indignant amazement of the
minister’s congregation. It almost cost him his pulpit, but he held on
and triumphed. There is no reason to believe that he ever repented of
his choice, or, rather, of Nance’s. To be sure, she had kidnapped him
by a lie; but perhaps she had wiped it out by fifty years of honest
affection. On that point, however, I, who tell the tale, will not
dogmatize.
[Illustration]
SONG.
BY THOMAS LOVELL BEDDOES.
From “Torrismond,” Sc. iii.
_How many times do I love thee, dear?_
_Tell me how many thoughts there be_
_In the atmosphere_
_Of a new fall’n year,_
_Whose white and sable hours appear_
_The latest flake of eternity--_
_So many times do I love thee, dear._
_How many times do I love, again?_
_Tell me how many beads there are_
_In a silver chain_
_Of evening rain_
_Unravelled from the tumbling main_
_And threading the eye of a yellow star--_
_So many times do I love again._
FOUR HUNDRED DEGREES BELOW ZERO.
AN INTERVIEW WITH PROFESSOR JAMES DEWAR.
BY HENRY J. W. DAM.
The science of chemistry, like that of geography, has its undiscovered
North Pole. Four hundred and sixty-one degrees below the freezing point
of the Fahrenheit thermometer (−274° C.) lies a mysterious, specially
indicated degree of cold which science has long been gazing toward and
striving to attain, wondering meanwhile what may be the conditions
of matter at this unexplored point. Its existence has long been
indicated and its position established in two different ways, viz.,
the regularly diminishing volumes of gases, and the steady falling off
in the resistance made by pure metals to the passage through them of
electricity under increasing degrees of cold. This point, to which both
these processes tend as an ultimate, is called the zero of absolute
temperature. By more than one eminent observer it is supposed to be
the temperature of inter-stellar space, the normal temperature of the
universe. Whether or not this supposition be correct, the efforts which
have been made and are still in progress to reach this degree of cold
have been many, diverse, and ingenious; the equipment of the explorer
being not boats, condensed foods, and the general machinery of ice
exploration, but all the varied resources of mechanics and of chemistry
which can be combined to compass the extremest degrees of cold.
All the world has heard of Professor James Dewar, and of his late great
triumphs in the liquefaction of oxygen gas and the solidification of
nitrogen and air. The sensation caused by his extraordinary results won
him at once the congratulations of many scientific men, the profuse
encomiums of the press, and the flattering recognition of appreciative
royal personages. This was largely due to the fact that in the search
for this unknown and mysterious point he had plunged much deeper than
any chemist before him into the regions of low temperature, and had
arrived within sixty degrees Centigrade of the point itself. This
exciting and not uneventful journey downward did not take him beyond
the confines of his own laboratory, but his description of it, as well
as of the properties of matter under extreme cold, has something of
the fascination, to the mind possessed of ordinary chemical curiosity,
of the story of a Stanley, a Nansen, or a Peary, describing the
peculiarities of countries in which they, of all men, have been the
first to set their feet.
Professor Dewar, who was born in Kincardine-on-Forth in 1842, was
educated at the University of Edinburgh, where his natural and special
gifts as a chemist were developed by Sir Lyon Playfair, at that
time Professor of Chemistry in the university. The perspicacity and
tenacity of purpose which are characteristic of so many Scotchmen were
eminently the inheritance of Sir Lyon’s young assistant, and between
that period and the present a long series of original investigations
in all departments of chemistry have won for Professor Dewar at his
prime the Jacksonian Professorship of Natural Experimental Philosophy
at Cambridge University, the Fullerian Professorship of Chemistry at
the Royal Institution, the Fellowship of the Royal Society, the degree
of Doctor of Laws, and other dignities, which make great alphabetical
richness after his name upon scientific occasions of state. Personally,
he is of middle height and strong build, with a clearly cut face, full
of character. His speech, faintly flavored with the accent of Scotia,
is exact and emphatic; and his manner, whether he is concentrated
upon a scientific demonstration in his laboratory or traversing the
speculative questions of the hour in ordinary conversation in his
drawing-room, has the earnestness of the profound scientist, very
agreeably tempered by the polish of the traveller and cosmopolitan man
of the world. His absorption in scientific pursuits has not denied
him a very marked esthetic development, and his residential suite of
apartments at the Royal Institution is filled with treasures, rare
tapestries, bronzes, and carvings, picked up at continental dépôts or
purchased at the sales of great collections, which would make a highly
interesting article in themselves. To her husband’s scientific sense of
the value of age in wines, Mrs. Dewar adds her original researches in
the matter of choice teas, and it is averred by the eminent membership
of the Royal Institution that the degree of domestic civilization which
prevails on the third floor of the building is quite as high and more
potentially attractive than the stage of scientific civilization which
rules in the theatre, the libraries, and the laboratories of the floors
below. Like most Scotchmen, however, Professor Dewar is simple in his
tastes, and is more deeply stirred by a frozen gas or an antique bronze
than anything in the way of bisques or _suprêmes_. His heart, which
shows no signs of low temperature, is mainly in his laboratory, and he
leads the way there, down a flight of stone steps to the basement, with
a readiness that very clearly exhibits his latent enthusiasm.
[Illustration: THE LABORATORY OF DAVY AND FARADAY AT THE ROYAL
INSTITUTION.]
Moreover, it is a laboratory eminently calculated to excite the
enthusiasm of anybody, being, in fact, the most famous laboratory known
to chemical science. The workshop of Sir Humphry Davy, Michael Faraday,
and Doctor Thomas Young, to say nothing of lesser and still famous
men, it is a nest in which more great discoveries have been hatched
than any other of its kind on earth. Here it was that Young conducted
the experiments which gave us the undulatory theory of light. Here
Davy, covering, nearly a hundred years ago, almost the whole field of
chemistry and electricity, made clear those principles which science
and applied science since his time have developed to the marvellous
degrees of to-day. A little room leading to the right of the main
laboratory was the scene of all Faraday’s experiments in magnetism, and
a cellar on its south side is known to this day as “Davy’s Froggery,”
from the fact that Davy kept in it hundreds of live frogs for use in
his experiments. Professor Dewar, whose sense of the inspiration of
his surroundings is clearly deep, dwells upon them with interest,
and tells how on one occasion a barrel of live frogs, imported by
Davy from France, burst at the docks, causing astonishment there and
consternation in the laboratory when Davy learned of his loss. It was
in this laboratory that Faraday first liquefied chlorine gas, sending
thereupon that famously curt note to Dr. Paris, the biographer of Davy,
in 1823:
“DEAR SIR:--The oil you noticed yesterday turns out to be
liquid chlorine.
“Yours faithfully,
“MICHAEL FARADAY.”
All of Faraday’s work in the liquefaction of gases, the discovery of
new hydrocarbons, the study of the changes of steel through the slight
admixture of other metals, the improvement of optical glass, and the
long list of results which are to-day represented in millions of tons
of products from thousands of factories, were obtained within these
four walls. And nothing could better illustrate the earnestness and
modesty of the great chemist than a little anecdote which Professor
Dewar, standing in the centre of the room, calls to mind. “I never met
Faraday,” says he, “but Tyndall told me this story of him. The first
time Tyndall entered this laboratory, Faraday led him to this point and
said: ‘Tyndall, this is a sacred spot. This is the spot on which Davy
separated sodium and potassium.’”
The laboratory of to-day, however, looks very little like a scene of
chemical industry. It has more the air of a machine shop, equipped
with power and mechanical appliances of a very heavy kind. Instead of
bottles and multi-colored liquids, all is metal and steam. The room
is about thirty feet wide and fifty deep, the north front consisting
entirely of glass windows opening on a well-lighted interior court.
In the left-hand corner, at the back, is a large steam-engine, while
a smaller one occupies the corner diagonally across. Shafts, wheels,
and belting run to two large air-pumps and three steel compressors,
each about the size and shape of a small travelling trunk, and used
respectively for compressing oxygen, nitrous oxide, and ethylene. A
fourth compressor, or double compressing chamber, is cylindrical in
form, and is wrapped in thick white flannel. This is the source of the
liquefied oxygen. The system which Professor Dewar has followed is not
novel in its general principles, as he explains. Specifically, however,
it contains many new inventions which he does not wish made public.
They are mainly in the nature of stop-cocks and valves, which it took
long study to invent, and which became perfect only after many failures
and costly experiments. To liquefy oxygen, he simply used pressure at
low temperatures; but as, up to 1878, both oxygen and nitrogen after
repeated trials were looked upon as permanent gases, it may be imagined
that the attainment of temperatures low enough was a problem which
required an extraordinary command of mechanics as well as of chemistry
to practically solve.
[Illustration: PROFESSOR DEWAR IN THE LABORATORY OF THE ROYAL
INSTITUTION. FROM A PHOTOGRAPH TAKEN FOR M’CLURE’S MAGAZINE BY FRADELLE
AND YOUNG, LONDON.]
“The process of liquefying oxygen, briefly speaking,” says the
professor, “is this. Into the outer chamber of that double compressor I
introduce, through a pipe, liquid nitrous oxide gas, under a pressure
of about 1,400 pounds to the square inch. I then allow it to evaporate
rapidly, and thus obtain a temperature around the inner chamber of
−90° C. (−130° F.). Into this cooled inner chamber I introduce
liquid ethylene, which is a gas at ordinary temperatures, under a
pressure of 1,800 pounds to the square inch. When the inner chamber
is full of ethylene, its rapid evaporation under exhaustion reduces
the temperature to −145° C. (−229° F.). Running through this inner
chamber is a tube containing oxygen gas under a pressure of 750 pounds
to the square inch. The ‘critical point’ of oxygen gas, that is, the
point above which no amount of pressure will reduce it to a liquid,
is −115° C., but this pressure, at the temperature of −145° C., is
amply sufficient to cause it to liquefy rapidly. In drawing off the
liquid under this pressure, I lose nine-tenths of it by evaporation,
and I have not yet seen how to diminish that loss. Every pint of it
which I collect therefore represents ten pints manufactured. In all,
I have thus far collected and used about fifty gallons, and the cost
of machinery and experiments, very generously met by subscription
among members of the Royal Institution and others, has been about
five thousand pounds sterling.” It should be here stated that one of
the most generous contributors to the fund has been Professor Dewar
himself, a large fraction of the sum having come out of his own pocket.
[Illustration: THE LECTURE-ROOM OF THE ROYAL INSTITUTION.]
Going more into detail, he makes clear some of the mechanical and
chemical difficulties which beset him in the work. “The secret of my
success,” he continues, “has been the mechanical arrangements combined
with the use of ethylene. This is a volatile hydrocarbon, and is the
chief illuminating constituent of coal gas. The only means of keeping
it liquid for any length of time is to surround it with solid carbonic
acid. Faraday was the first to call attention to the properties of
ethylene, and we manufacture it by heating sulphuric acid in a glass
retort protected by an iron cover to 160° C. Alcohol heated to 160°
C. is allowed to drip into it and ethylene results, passing off as a
gas, which is stored, after being purified. It is then compressed by
two pumps, the first with a six-inch plunger and six-inch stroke, and
the second a two-inch plunger and six-inch stroke. This liquefies it
under the pressure stated. It is nasty stuff to handle, as, whenever
it becomes mixed, by leakage or otherwise, with nitrous oxide or air,
an explosion is imminent, and we have had not a few explosions in the
course of the work. It liquefies at −103° C. (−152.4° F.), and when
boiled in a partial vacuum absorbs a large amount of latent heat.
The failure of preceding attempts to liquefy oxygen is due to lack
of knowledge of its ‘critical point,’ and the law which that phrase
describes. As long ago as 1851, Natterer subjected oxygen to a pressure
of 2,800 atmospheres, or over thirty tons to the square inch. He
obtained no result, because, as I have said, no amount of pressure will
affect it above −115° C. I liquefy it at −145° C. for two reasons.
The lower the temperature at which it is liquefied, the less is the
pressure required upon the oxygen and the greater is the amount of
latent heat which it absorbs in evaporating. By evaporating, under
exhaustion, oxygen liquefied at −145° C., I get as low as −200° C.,
which I could not do were it liquefied at a higher temperature.
[Illustration: PROFESSOR DEWAR’S LECTURE-TABLE. FROM A PHOTOGRAPH TAKEN
OF PROFESSOR DEWAR’S FIRST LECTURE ON THE LIQUEFACTION OF OXYGEN.]
“Having obtained the liquid oxygen,” he continues, turning to the long
table below the windows, “the question was how to store it for working
purposes, with the least possible loss by evaporation. After various
trials and experiments, we devised a set of vacuum vessels, each
consisting of a tube or bottle for the liquid oxygen, sealed at the
neck in a second tube or bottle, from which the air had been exhausted.
I found the cheapest and best method of getting a vacuum to be the old
Torricellian one of driving out the air with mercury vapor and then
condensing the vapor. This had a further advantage. The tube containing
the liquid oxygen was so cold that it froze the mercury vapor, and
coated itself with a perfect metallic mirror, which by its reflection
still further diminished the loss by radiated heat from the outside.”
Without more ado, he lifted from a small frame one of the vacuum
vessels referred to. It was a white glass jar, inside of which was what
seemed to be a round metallic ball. Open at the neck, this ball was a
bottle nearly filled with liquid oxygen, and by the light which reached
it through the neck of the bottle it was a very clear pale blue liquid,
which was evaporating quietly in a single thread of tiny bubbles, like
a glass of champagne which has become nearly still.
It was one of those moments which Faraday would doubtless have
regarded as solemn. To behold, for the first time, a liquid which
your professors of chemistry have assured you was a gas and always
would be a gas, is an experience which does not occur many times in a
lifetime. After that, a sight of perpetual motion or the square of the
circle would leave you calm. To know, furthermore, that this strange
gas, which is the prime agent of all life, which is eight-ninths of
all water and three-fourths of the entire earth, has been laid captive
by science, reduced to a form which cannot fail to shed a flood of
light on any number of abstruse problems in chemistry and mechanics,
excites a deeper feeling. The pale blue liquid, which is strangely
lustrous, seems truly magical. Moreover, it is a great surprise to see
the liquid, which you expect to find under great pressure and ready to
blow its containing vessel to pieces, evaporating quietly in the air,
protected from heat by a vacuum on one side and its own cold vapor on
the other. And so you can do nothing but stare at it in amazement, and
gently shake the bottle, and turn from it to its discoverer with a
feeling which is not entirely dissociated from awe. It has lost all
its impressiveness to the professor, however, for he is busy preparing
to illustrate some of its properties--an interesting introduction in
themselves to the conditions which prevail twice as far below the
freezing point of water as its boiling point lies above.
[Illustration: EARLY AND LATEST FORMS OF VESSELS FOR HOLDING LIQUEFIED
OXYGEN.]
He begins by pouring some of the oxygen into a test tube, white fumes
appearing as he does so from the freezing of the moisture in the
surrounding air. Then he drops into the liquid oxygen in the test tube
a bit of phosphorus. Despite the flaming energy with which these two
combine at ordinary temperatures, there is no action. The phosphorus is
as unaffected as a chip of wood in water. He takes it out and pours in
some pure alcohol, whose freezing point is much below that of mercury.
It freezes with a slight sputter into what you can only call alcohol
ice. He takes out the ice and holds a match to it. There is no sign
of combustion. Placed on a glass dish the alcohol ice melts into a
thick, oily liquid, which also declines to burn. In a few seconds,
however, it warms to its ordinary thinness and burns as hungrily as
ever. Then comes an exhibition of the “spheroidal state.” A drop of
water thrown towards a red-hot stove does not touch the stove, because
the evaporation is so rapid that the forming gas lifts the water and
keeps it moving about. Precisely the same thing occurs when the oxygen
is dropped over a flat glass dish at the temperature of the air, which
is red-hot to the oxygen, comparatively speaking. It dances about,
shaking and boiling furiously. As he pours it, a tiny drop splashes
on the professor’s hand, and he flings it off with a quick jerk. “It
makes a sore worse than a burn,” he explains, “if it ever touches the
skin.” Then he drops some of it into water. It floats quietly, and
as it boils off into gas, freezes a cup of water around it, floating
about comfortably in its own boat. Then came curious evidence of its
magnetic properties. Pouring a little into a flat cup of rock salt,
he placed the cup between the poles of an electro-magnet, the one
which Faraday used. The boiling liquid, the moment that the circuit
was completed, flew to the two terminals _en masse_ and clung there,
still boiling away rapidly on the two points. A piece of cotton wool
soaked in the liquid was held closely to one of the points, until all
the oxygen had been sucked out of it, when it hung suspended between
them. Liquid oxygen has a magnetic property, he said, which is about
1,000 as compared with 1,000,000, the magnetic property of iron. It is
a non-conductor of electricity, and a spark one-tenth of a millimetre
long from a coil machine, which would give a long spark in the air,
would not pass through the liquid. It gave a flash now and then as a
bubble of oxygen vapor came between the terminals. Liquid oxygen is, in
fact, a high insulator.
Liquid oxygen at atmospheric pressure boils at −184° C. (−229.2°
F.). By evaporating it under a diminished pressure, he gets much
higher degrees of cold, and these have enabled him to both liquefy
and solidify nitrogen and air. The experiment illustrating this
was not only interesting; it was difficult to believe. In a double
vacuum vessel the centre of which was an open test tube, and the
second compartment a reservoir of liquid oxygen connected with an
exhaust pump, he so lowered the pressure that the oxygen boiled
tumultuously. As it did so, drops of clear liquid began to form on
the sides of the test tube and gather at the bottom. It was liquid
air, the oxygen and nitrogen of the atmosphere liquefying together at
a temperature of −197.2° (−322.9° F.). He poured some of the liquid
air into a second tube, and then showed how the nitrogen, which
liquefies at a temperature fourteen degrees below oxygen, boiled off
first. A smouldering splinter of wood held at the mouth of the tube
was extinguished. A few moments later when it was again held there,
it burst into brilliant flame. The nitrogen had all evaporated, and
the oxygen was coming off. He explained that air became solid under
pressure at −207° C. (−340.6° F.). It was a structureless glass, and
he had not determined whether or not the oxygen in it was solid or
was held suspended as a jelly. Nitrogen solidified under pressure at
−210° C. (−346° F.). It was a white crystalline substance. He had no
knowledge as yet whether oxygen crystallized in solidifying, but his
belief was that it would not.
[Illustration: THE “COMPRESSORS.”]
Concerning hydrogen, most elusive of all the gases, he had no present
expectation of attaining liquefaction. Its critical point was below
−210° C., and its boiling point −250° C. He had no means as yet of
attacking the problem. In fact, the only thermometer he was able to
use at these low temperatures was one which used hydrogen expansion
as a measure of temperature. His main reliance in measuring low
temperatures was a thermo-electric junction. Deeply interesting also
was his description of liquid ozone, that strange form of oxygen which
though identical with it in constitution is different in molecular
arrangement. He obtains twenty per cent. of ozone from liquid oxygen
by electrical stimulation, the ozone being of a very dark blue color,
as dark as concentrated indigo. It is highly unstable, a beam of light
having caused it to explode on one occasion, and its study even in
small quantities requires all the delicacy of manipulation which is
one of the special directions in which Professor Dewar as a chemist
occupies the foremost rank.
Through all these explanations, and others too elaborate and too
technical for these pages, he had spoken in the clear, emphatic way
which is characteristic of men who deal with abstruse subjects, and
desire, from long habit, to present them with the maximum of clearness
and the minimum of words. His speech is incisive, the utterances of an
energetic and concentrated mind. Over a cup of tea upstairs, however,
he spoke more slowly and dwelt with interest upon some of the many
strange results which have already met his eyes in the region of −200°
Centigrade.