Read The Faber Book of Science Online
Authors: John Carey
Joseph Priestley (1733–1804) was a Unitarian minister and schoolteacher. A keen supporter of the American and French Revolutions, he confessed that he had tended, from an early age, ‘to embrace what is generally called the heterodox side of almost every question’.
Introduced to science by Benjamin Franklin, whom he met in London, Priestley made experiments on the ‘air’ (the current name for a gas) given off by the fermenting liquors in the brewery next door to his house in Leeds. This was carbon dioxide and, dissolving it in water, Priestley invented soda water, for which the Royal Society gave him a medal in 1773.
He then turned his attention to the ‘airs’ given off when various substances were heated. To examine these he constructed a simple apparatus, described in his
Experiments
and
Observations
on
Different
Kinds
of
Air
(1775), consisting of a trough full of mercury, over which glass vessels could be inverted to collect the gas. The substance to be heated was placed in another glass vessel on the surface of the mercury, and Priestley focused the sun’s rays on it using a 12-inch lens.
To test his gases Priestley employed mice, which he caught in wire traps, and introduced into the gas-filled vessels. Should the gas be likely to prove noxious, he warned, ‘it will be proper (if the operator be desirous of preserving the mice for further use) to keep hold of their tails, that they may be withdrawn as soon as they begin to show signs of uneasiness’.
When Priestley heated red mercuric oxide (which he calls
mercurius
calcinatus
per
se
),
using his apparatus, it gave off a colourless gas which, as he describes in the following account, made a candle flame burn brightly. Like other eighteenth–century scientists, Priestley believed that all combustible materials contained an element called ‘phlogiston’, which was given off when they burned. Air in which things had been burned became less able to support combustion because, it was thought, it was saturated with ‘phlogiston’. Accordingly Priestley called his gas in which a candle flame burned brightly ‘dephlogisticated air’. In fact it was oxygen.
The contents of this section will furnish a very striking illustration of the truth of a remark, which I have more than once made in my
philosophical writings, and which can hardly be too often repeated, as it tends greatly to encourage philosophical investigations viz. that more is owing to what we call
chance
, that is, philosophically speaking, to the observation of events arising from
unknown
causes
, then to any proper
design
, or pre-conceived theory in this business.
For my own part, I will frankly acknowledge, that, at the commencement of the experiments recited in this section, I was so far from having formed any hypothesis that led to the discoveries I made in pursuing them, that they would have appeared very improbable to me had I been told of them; and when the decisive facts did at length obtrude themselves upon my notice, it was very slowly, and with great hesitation, that I yielded to the evidence of my senses … [Priestley then recounts the construction of the mercury-trough apparatus described above.]
With this apparatus, after a variety of other experiments, an account of which will be found in its proper place, on the 1st of August, 1774, I endeavoured to extract air from
mercurius
calcinatus
per
se;
and I presently found that, by means of the lens, air was expelled from it very readily. Having got about three or four times as much as the bulk of my materials, I admitted water to it, and found that it was not imbibed by it. But what surprised me more than I can well express, was, that a candle burned in this air with a remarkably vigorous flame …
I cannot, at this distance of time, recollect what it was that I had in view in making this experiment: but I know I had no expectation of the real issue of it. Having acquired a considerable degree of readiness in making experiments of this kind, a very slight and evanescent motive would be sufficient to induce me to do it. If, however, I had not happened, for some other purpose, to have had a lighted candle before me, I should probably never have made the trial; and the whole train of my future experiments relating to this kind of air might have been prevented …
In this case, also, though I did not give sufficient attention to the circumstance at that time, the flame of the candle, besides being larger, burned with more splendour and heat… and a piece of red-hot wood sparkled in it, exactly like paper dipped in a solution of nitre, and it consumed very fast …
On the 8th of this month [March, 1775] I procured a mouse, and put it into a glass vessel, containing two one-ounce measures of the air
from mercurius calcinatus. Had it been common air, a full-grown mouse, as this was, would have lived in it about a quarter of an hour. In this air, however, my mouse lived a full half hour; and though it was taken out seemingly dead, it appeared to have been only exceedingly chilled; for, upon being held to the fire, it presently revived, and appeared not to have received any harm from the experiment.
… By this I was confirmed in my conclusion, that the air extracted from mercurius calcinatus, &c. was,
at
least,
as
good
as common air; but I did not certainly conclude that it was any
better;
because, though one mouse would live only a quarter of an hour in a given quantity of air, I knew it was not impossible but that another mouse might live in it half an hour; so little accuracy is there in this method of ascertaining the goodness of air …
For my farther satisfaction I procured another mouse, and putting it into less than two ounce-measures of air extracted from mercurius calcinatus and air from red precipitate (which, having found them to be of the same quality, I had mixed together) it lived three quarters of an hour. But not having had the precaution to set the vessel in a warm place, I suspect that the mouse died of cold. However, as it had lived three times as long as it could probably have lived in the same quantity of common air, and I did not expect much accuracy from this kind of test, I did not think it necessary to make any more experiments with mice.
It may hence be inferred, that a quantity of very pure air would agreeably qualify the noxious air of a room in which much company should be confined, and which should be so situated, that it could not be conveniently ventilated; so that from being offensive and
unwholesome
, it would almost instantly become sweet and wholesome. This air might be brought into the room in casks; or a laboratory might be constructed for generating the air, and throwing it into the room as fast as it should be produced. This pure air would be sufficiently cheap for the purpose of many assemblies, and a very little ingenuity would be sufficient to reduce the scheme into practice …
From the greater strength and vivacity of the flame of a candle, in this pure air, it may be conjectured, that it might be peculiarly salutary to the lungs in certain morbid cases, when the common air would not be sufficient to carry off the phlogistic putrid effluvium fast enough. But, perhaps, we may also infer from these experiments, that though pure dephlogisticated air might be very useful as
medicine,
it might not
be so proper for us in the usual healthy state of the body: for, as a candle burns out much faster in dephlogisticated than in common air, so we might, as may be said,
live
out
too
fast,
and the animal powers be too soon exhausted in this pure kind of air. A moralist, at least, may say, that the air which nature has provided for us is as good as we deserve.
My reader will not wonder, that, after having ascertained the superior goodness of dephlogisticated air by mice living in it, and the other tests above mentioned, I should have the curiosity to taste it myself. I have gratified that curiosity, by breathing it, drawing it through a glass-syphon, and, by this means, I reduced a large jar full of it to the standard of common air. The feeling of it to my lungs was not sensibly different from that of common air; but I fancied that my breast felt peculiarly light and easy for some time afterwards. Who can tell but that, in time, this pure air may become a fashionable article in luxury. Hitherto only two mice and myself have had the privilege of breathing it …
Being at Paris in the October following, and knowing that there were several very eminent chemists in that place … I frequently mentioned my surprise at the kind of air which I had got from this preparation to Mr Lavoisier, Mr le Roy, and several other
philosophers
, who honoured me with their notice in that city; and who, I daresay, cannot fail to recollect the circumstance.
The eminent French chemist Antoin-Laurent Lavoisier (1743–94), to whom Priestley divulged his discovery, understood the theoretical implications of it, as Priestley did not. Lavoisier had already announced, in 1772, that he was ‘destined to bring about a revolution in physics and chemistry’. Unlike the older scientists he realized that atmospheric air was not an ‘element’ but a compound of gases, and he identified Priestley’s discovery as the active component of air for which he had been searching. He called it ‘oxygen’ (Greek: ‘acid former’), in the belief that all acids contained it. In 1783 he made public his complete renovation of chemical theory, and Mme Lavoisier ceremonially burned the books of the phlogiston theorists to mark the new era. Unfortunately Lavoisier, who had been a tax-collector under the
ancien
régime
‚
was guillotined at the time of the French Revolution.
Source: Joseph Priestley,
Experiments
and
Observations
on
Different
Kinds
of
Air,
London, 1775.
The planet Uranus was discovered by the German-born British astronomer William Herschel (1738–1822). The son of an army musician, Herschel came to England in 1757 to follow a musical career, as teacher, composer and performer, and became organist of a fashionable chapel in Bath. An amateur astronomer, he constructed new and powerful telescopes, grinding the mirrors himself, and it was through one of those that, in 1781, he saw Uranus, the first planet to be discovered since prehistoric times. Fame, and a
£
200-per-year pension from George III, quickly followed, and Herschel gave up music for full-time astronomy. He developed a theory of the evolution of stars, and was the first to hypothesize that nebulae (misty white patches among the stars, visible through a telescope) were clouds of individual stars, forming separate galaxies.
Uranus takes 84.01 years to orbit the sun. It is an extremely cold planet, and is thought to consist of a rocky core and an ice mantle 8,000 kilometres thick. Nine of its twenty rings were discovered in 1977; the rest were photographed by the Voyager 2 probe in 1986.
Though not a very good poet, Alfred Noyes (1880–1958) was singular in that he wrote a modern epic poem about the progress of science,
The
Torch-
Bearers
.
In the following extract (heavily indebted to Robert Browning’s dramatic monologues), Noyes imagines Herschel’s thoughts while conducting a concert in Bath.
My periwig’s askew, my ruffle stained
With grease from my new telescope!
Ach, to-morrow
How Caroline will be vexed, although she grows
Almost as bad as I, who cannot leave
My workshop for one evening.
I must give
One last recital at St Margaret’s,
And then – farewell to music.
Who can lead
Two lives at once?
Yet – it has taught me much,
Thrown curious lights upon our world, to pass
From one life to another. Much that I took
For substance turns to shadow. I shall see
No throngs like this again; wring no more praise
Out of their hearts; forego that instant joy
– Let those who have not known it count it vain –
When human souls at once respond to yours.
Here, on the brink of fortune and of fame,
As men account these things, the moment comes
When I must choose between them and the stars;
And I have chosen.
Handel, good old friend,
We part to-night. Hereafter, I must watch
That other wand, to which the worlds keep time.
What has decided me? That marvellous night
When – ah, how difficult it will be to guide,
With all these wonders whirling through my brain!
After a Pump-room concert I came home
Hot-foot, out of the fluttering sea of fans,
Coquelicot-ribboned belles and periwigged beaux,
To my Newtonian telescope.
The design
Was his; but more than half the joy my own,
Because it was the work of my own hand,
A new one, with an eye six inches wide,
Better than even the best that Newton made
Then, as I turned it on the
Gemini,
And the deep stillness of those constant lights,
Castor and Pollux, lucid pilot-stars,
Began to calm the fever of my blood,
I saw, O, first of all mankind I saw
The disk of my new planet gliding there
Beyond our tumults, in that realm of peace.
What will they christen it? Ach – not
Herschel,
no!
Not
Georgium
Sidus,
as I once proposed;
Although he scarce could lose it, as he lost
That world in ’seventy-six.
Indeed, so far
From trying to tax it, he has granted me
How much? – two hundred golden pounds a year,
In the great name of science, – half the cost
Of one state-coach, with all those worlds to win! …
To-night,
– The music carries me back to it again! –
I see beyond this island universe,
Beyond our sun, and all those other suns
That throng the Milky Way, far, far beyond,
A thousand little wisps, faint nebulae,
Luminous fans and milky streaks of fire;
Some like soft brushes of electric mist
Streaming from one bright point; others that spread
And branch, like growing systems; others discrete,
Keen, ripe, with stars in clusters; others drawn back
By central forces into one dense death,
Thence to be kindled into fire, reborn,
And scattered abroad once more in a delicate spray
Faint as the mist by one bright dewdrop breathed
At dawn, and yet a universe like our own;
Each wisp a universe, a vast galaxy
Wide as our night of stars.
The Milky Way
In which our sun is drowned, to these would seem
Less than to us their faintest drift of haze;
Yet we, who are borne on one dark grain of dust
Around one indistinguishable spark
Of star-mist, lost in one lost feather of light,
Can by the strength of our own thought, ascend
Through universe after universe; trace their growth
Through boundless time, their glory, their decay;
And, on the invisible road of law, more firm
Than granite, range through all their length and breadth,
Their height and depth, past, present, and to come.
Alfred Noyes,
The
Torch-Bearers,
London, Sheed & Ward, 1937.