Experiments and Observations on Different Kinds of Air Part 1

Experiments and Observations on Different Kinds of Air.

by Joseph Priestley.

PREFACE.

One reason for the present publication has been the favourable reception of those of my _Observations on different kinds of air_, which were published in the Philosophical Transactions for the year 1772, and the demand for them by persons who did not chuse, for the sake of those papers only, to purchase the whole volume in which they were contained.

Another motive was the _additions_ to my observations on this subject, in consequence of which my papers grew too large for such a publication as the _Philosophical Transactions_.

Contrary, therefore, to my intention, expressed Philosophical Transactions, vol. 64. p. 90, but with the approbation of the President, and of my friends in the society, I have determined to send them no more papers for the present on this subject, but to make a separate and immediate publication of all that I have done with respect to it.

Besides, considering the attention which, I am informed, is now given to this subject by philosophers in all parts of Europe, and the rapid progress that has already been made, and may be expected to be made in this branch of knowledge, all unnecessary delays in the publication of experiments relating to it are peculiarly unjustifiable.

When, for the sake of a little more reputation, men can keep brooding over a new fact, in the discovery of which they might, possibly, have very little real merit, till they think they can astonish the world with a system as complete as it is new, and give mankind a prodigious idea of their judgment and penetration; they are justly punished for their ingrat.i.tude to the fountain of all knowledge, and for their want of a genuine love of science and of mankind, in finding their boasted discoveries antic.i.p.ated, and the field of honest fame pre-occupied, by men, who, from a natural ardour of mind, engage in philosophical pursuits, and with an ingenuous simplicity immediately communicate to others whatever occurs to them in their inquiries.

As to myself, I find it absolutely impossible to produce a work on this subject that shall be any thing like _complete_. My first publication I acknowledged to be very imperfect, and the present, I am as ready to acknowledge, is still more so. But, paradoxical as it may seem, this will ever be the case in the progress of natural science, so long as the works of G.o.d are, like himself, infinite and inexhaustible. In completing one discovery we never fail to get an imperfect knowledge of others, of which we could have no idea before; so that we cannot solve one doubt without creating several new ones.

Travelling on this ground resembles Pope's description of travelling among the Alps, with this difference, that here there is not only _succession_, but an _increase_ of new objects and new difficulties.

So pleas'd at first the tow'ring Alps we try, Mount o'er the vales, and seem to tread the sky.

Th' eternal snows appear already past, And the first clouds and mountains seem the last, But those attain'd, we tremble to survey The growing labours of the lengthen'd way.

Th' increasing prospect tires our wand'ring eyes, Hills peep o'er hills, and Alps on Alps arise.

ESSAY ON CRITICISM.

Newton, as he had very little knowledge of _air_, so he had few doubts concerning it. Had Dr. Hales, after his various and valuable investigations, given a list of all his _desiderata_, I am confident that he would not have thought of one in ten that had occurred to me at the time of my last publication; and my doubts, queries, and hints for new experiments are very considerably increased, after a series of investigations, which have thrown great light upon many things of which I was not able to give any explanation before.

I would observe farther, that a person who means to serve the cause of science effectually, must hazard his own reputation so far as to risk even _mistakes_ in things of less moment. Among a multiplicity of new objects, and new relations, some will necessarily pa.s.s without sufficient attention; but if a man be not mistaken in the princ.i.p.al objects of his pursuits, he has no occasion to distress himself about lesser things.

In the progress of his inquiries he will generally be able to rectify his own mistakes; or if little and envious souls should take a malignant pleasure in detecting them for him, and endeavouring to expose him, he is not worthy of the name of a philosopher, if he has not strength of mind sufficient to enable him not to be disturbed at it. He who does not foolishly affect to be above the failings of humanity, will not be mortified when it is proved that he is but a man.

In this work, as well as in all my other philosophical writings, I have made it a rule not to conceal the _real views_ with which I have made experiments; because though, by following a contrary maxim, I might have acquired a character of greater sagacity, I think that two very good ends are answered by the method that I have adopted. For it both tends to make a narrative of a course of experiments more interesting, and likewise encourages other adventurers in experimental philosophy; shewing them that, by pursuing even false lights, real and important truths may be discovered, and that in seeking one thing we often find another.

In some respects, indeed, this method makes the narrative _longer_, but it is by making it less tedious; and in other respects I have written much more concisely than is usual with those who publish accounts of their experiments. In this treatise the reader will often find the result of long processes expressed in a few lines, and of many such in a single paragraph; each of which, if I had, with the usual parade, described it at large (explaining first the _preparation_, then reciting the _experiment_ itself, with the _result_ of it, and lastly making suitable _reflections_) would have made as many sections or chapters, and have swelled my book to a pompous and respectable size. But I have the pleasure to think that those philosophers who have but little time to spare for _reading_, which is always the case with those who _do_ much themselves, will thank me for not keeping them too long from their own pursuits; and that they will find rather more in the volume, than the appearance of it promises.

I do not think it at all degrading to the business of experimental philosophy, to compare it, as I often do, to the diversion of _hunting_, where it sometimes happens that those who have beat the ground the most, and are consequently the best acquainted with it, weary themselves without starting any game; when it may fall in the way of a mere pa.s.senger; so that there is but little room for boasting in the most successful termination of the chace.

The best founded praise is that which is due to the man, who, from a supreme veneration for the G.o.d of nature, takes pleasure in contemplating his _works_, and from a love of his fellow-creatures, as the offspring of the same all-wise and benevolent parent, with a grateful sense and perfect enjoyment of the means of happiness of which he is already possessed, seeks, with earnestness, but without murmuring or impatience, that greater _command of the powers of nature_, which can only be obtained by a more extensive and more accurate _knowledge_ of them; and which alone can enable us to avail ourselves of the numerous advantages with which we are surrounded, and contribute to make our common situation more secure and happy.

Besides, the man who believes that there is a _governor_ as well as a _maker_ of the world (and there is certainly equal reason to believe both) will acknowledge his providence and favour at least as much in a successful pursuit of _knowledge_, as of _wealth_; which is a sentiment that entirely cuts off all boasting with respect to ourselves, and all envy and jealousy with respect to others; and disposes us mutually to rejoice in every new light that we receive, through whose hands soever it be conveyed to us.

I shall pa.s.s for an enthusiast with some, but I am perfectly easy under the imputation, because I am happy in those views which subject me to it; but considering the amazing improvements in natural knowledge which have been made within the last century, and the many ages, abounding with men who had no other object but study, in which, however, nothing of this kind was done, there appears to me to be a very particular providence in the concurrence of those circ.u.mstances which have produced so great a change; and I cannot help flattering myself that this will be instrumental in bringing about other changes in the state of the world, of much more consequence to the improvement and happiness of it.

This rapid progress of knowledge, which, like the progress of a _wave_ of the sea, of _sound_, or of _light_ from the sun, extends itself not this way or that way only, but _in all directions_, will, I doubt not, be the means, under G.o.d, of extirpating _all_ error and prejudice, and of putting an end to all undue and usurped authority in the business of _religion_, as well as of _science_; and all the efforts of the interested friends of corrupt establishments of all kinds will be ineffectual for their support in this enlightened age: though, by r.e.t.a.r.ding their downfal, they may make the final ruin of them more complete and glorious. It was ill policy in Leo the Xth to patronize polite literature. He was cherishing an enemy in disguise. And the English hierarchy (if there be any thing unsound in its const.i.tution) has equal reason to tremble even at an air-pump, or an electrical machine.

There certainly never was any period in which _natural knowledge_ made such a progress as it has done of late years, and especially in this country; and they who affect to speak with supercilious contempt of the publications of the present age in general, or of the Royal Society in particular, are only those who are themselves engaged in the most trifling of all literary pursuits, who are unacquainted with all real science, and are ignorant of the progress and present state of it.[1]

It is true that the rich and the great in this country give less attention to these subjects than, I believe, they were ever known to do, since the time of Lord Bacon, and much less than men of rank and fortune in other countries give to them. But with us this loss is made up by men of leisure, spirit, and ingenuity, in the middle ranks of life, which is a circ.u.mstance that promises better for the continuance of this progress in useful knowledge than any n.o.ble or royal patronage. With us, politics chiefly engage the attention of those who stand foremost in the community, which, indeed, arises from the _freedom_ and peculiar _excellence_ of our const.i.tution, without which even the spirit of men of letters in general, and of philosophers in particular, who never directly interfere in matters of government, would languish.

It is rather to be regretted, however, that, in such a number of n.o.bility and gentry, so very few should have any taste for scientifical pursuits, because, for many valuable purposes of science, _wealth_ gives a decisive advantage. If extensive and lasting _fame_ be at all an object, literary, and especially scientifical pursuits, are preferable to political ones in a variety of respects. The former are as much more favourable for the display of the human faculties than the latter, as the _system of nature_ is superior to any _political system_ upon earth.

If extensive _usefulness_ be the object, science has the same advantage over politics. The greatest success in the latter seldom extends farther than one particular country, and one particular age; whereas a successful pursuit of science makes a man the benefactor of all mankind, and of every age. How trifling is the fame of any statesman that this country has ever produced to that of Lord Bacon, of Newton, or of Boyle; and how much greater are our obligations to such men as these, than to any other in the whole _Biographia Britannica_; and every country, in which science has flourished, can furnish instances for similar observations.

Here my reader will thank me, and the writer will, I hope, forgive me, if I quote a pa.s.sage from the postscript of a letter which I happen to have just received from that excellent, and in my opinion, not too enthusiastical philosopher, father Beccaria of Turin.

_Mi spiace che il mondo politico ch'e pur tanto pa.s.seggero, rubbi il grande Franklin al mondo della natura, che non sa ne cambiare, ne mancare._ In English. "I am sorry that the _political world_, which is so very transitory, should take the great Franklin from the _world of nature_, which can never change, or fail."

I own it is with peculiar pleasure that I quote this pa.s.sage, respecting this truly great man, at a time when some of the infatuated politicians of this country are vainly thinking to build their wretched and destructive projects, on the ruins of his established reputation; a reputation as extensive as the spread of science itself, and of which it is saying very little indeed, to p.r.o.nounce that it will last and flourish when the names of all his enemies shall be forgotten.

I think it proper, upon this occasion, to inform my friends, and the public, that I have, for the present, suspended my design of writing _the history and present state of all the branches of experimental philosophy_. This has arisen not from any dislike of the undertaking, but, in truth, because I see no prospect of being reasonably indemnified for so much labour and expence, notwithstanding the specimens I have already given of that work (in the _history of electricity_, and of the _discoveries relating to vision, light, and colours_) have met with a much more favourable reception from the best judges both at home and abroad, than I expected. Immortality, if I should have any view to it, is not the proper price of such works as these.

I propose, however, having given so much attention to the subject of _air_, to write, at my leisure, the history and present state of discoveries relating to it; in which case I shall, as a part of it, reprint this work, with such improvements as shall have occurred to me at that time; and I give this notice of it, that no person who intends to purchase it may have reason (being thus apprised of my intention) to complain of buying the same thing twice. If any person chuse it, he may save his five or six shillings for the present, and wait five or six years longer (if I should live so long) for the opportunity of buying the same thing, probably much enlarged, and at the same time a complete account of all that has been done by others relating to this subject.

Though for the plain, and I hope satisfactory reason above mentioned, I shall probably write no other _histories_ of this kind, I shall, as opportunity serves, endeavour to provide _materials_ for such histories, by continuing my experiments, keeping my eyes open to such new appearances as may present themselves, investigating them as far as I shall be able, and never failing to communicate to the public, by some channel or other, the result of my observations.

In the publication of this work I have thought that it would be agreeable to my readers to preserve, in some measure, the order of history, and therefore I have not thrown together all that I have observed with respect to each kind of air, but have divided the work into _two parts_; the former containing what was published before, in the Philosophical Transactions, with such observations and corrections as subsequent experience has suggested to me; and I have reserved for the latter part of the work an account of the experiments which I have made since that publication, and after a pretty long interruption in my philosophical pursuits, in the course of the last summer. Besides I am sensible that in the latter part of this work a different arrangement of the subjects will be more convenient, for their mutual ill.u.s.tration.

Some persons object to the term _air_, as applied to _acid_, _alkaline_, and even _nitrous air_; but it is certainly very convenient to have a common term by which to denote things which have so many common properties, and those so very striking; all of them agreeing with the air in which we breathe, and with _fixed air_, in _elasticity_, and _transparency_, and in being alike affected by heat or cold; so that to the eye they appear to have no difference at all. With much more reason, as it appears to me, might a person object to the common term _metal_, as applied to things so very different from one another as gold, quicksilver, and lead.

Besides, _acid_ and _alkaline_ air do not differ from _common air_ (in any respect that can countenance an objection to their having a common appellation) except in such properties as are common to it with _fixed air_, though in a different degree; viz. that of being imbibed by water.

But, indeed, all kinds of air, common air itself not excepted, are capable of being imbibed by water in some degree.

Some may think the terms acid and alkaline _vapour_ more proper than acid and alkaline _air_. But the term _vapour_ having always been applied to elastic matters capable of being condensed in the temperature of the atmosphere, especially the vapour of water, it seems harsh to apply it to any elastic substance, which at the same time that it is as transparent as the air we breathe, is no more affected by cold than it is.

As my former papers were immediately translated into several foreign languages, I may presume that this treatise, having a better t.i.tle to it, will be translated also; and, upon this presumption, I cannot help expressing a wish, that it may be done by persons who have a competent knowledge of _subject_, as well as of the _English language_. The mistakes made by some foreigners, have induced me to give this caution.

_London, Feb._ _1774._

ADVERTIs.e.m.e.nT.

The _weights_ mentioned in the course of this treatise are _Troy_, and what is called _an ounce measure of air_, is the s.p.a.ce occupied by an ounce weight of water, which is equal to 480 grains, and is, therefore, almost two _cubic inches_ of water; for one cubic inch weighs 254 grains.

FOOTNOTES:

[1] See Sir John Pringle's _Discourse on the different kinds of air_, p.

29, which, if it became me to do it, I would recommend to the reader, as containing a just and elegant account of the several discoveries that have been successively made, relating to the subject of this treatise.

THE INTRODUCTION.

SECTION I.

_A general view of PRECEDING DISCOVERIES relating to air._