Heads of Lectures on a Course of Experimental Philosophy: Particularly Including Chemistry.

by Joseph Priestley.

THE PREFACE.

Situated, as I happily am, in the neighbourhood of the _New College at Hackney_, an inst.i.tution that does honour to the Dissenters, an inst.i.tution open to all persons without distinction[1], and connected as I am by friendship with the tutors, I was glad to give it every a.s.sistance in my power; and therefore undertook to read the _Lectures on History and General Policy_ which I had composed when I was tutor at Warrington, and also to give another course on the subject of _Experimental Philosophy_. With this view I drew up the following _Heads of Lectures_; and, to save the students the trouble of transcribing them, they are now printed. To other persons they may serve as a compendious view of the most important discoveries relating to the subject.

[Footnote 1: One gentleman of the Roman Catholic persuasion, and several of the Church of England, are now in the College.]

As it was found most convenient, with respect to the other business of the college, to confine this course to one lecture in a week, I contrived to bring within that compa.s.s as much of the subject of experimental philosophy as I well could, and especially to include the whole of what is called _chemistry_, to which so much attention is now given, and which presents so many new fields of philosophical investigation.

Besides that the plan of the young gentlemen's studies would not admit of it, I think it most advisable not to trouble beginners with more than a large outline of any branch of science. By this means they are not fatigued by too long an attention to any one subject, a greater variety of articles may be brought before them, and in future life they may pursue any of them as much farther as their inclination may dispose, and their ability and opportunity shall enable, them to do it.

I do not give any account of the _experiments_ introduced into the several lectures. They will be sufficiently indicated by the subjects of them. They were as many as I could conveniently make within the time; and where the experiments themselves could not be made, I usually exhibited both the different substances employed in them, and those that were the result of them.

As these lectures were calculated for the use of the students at the New College, I prefix an _Address to them_, the same in substance with that which I delivered to them at the close of the session of 1791. In it may be seen a specimen of the language we hold to them on the subject of _politics_, which with reasonable men will serve as an answer to the many calumnies that have been thrown out against us, as disaffected to the government of this country.

Such inst.i.tutions will, indeed, always be objects of hatred and dread to _bigots_ and the advocates for _arbitrary power_, but the pride of a truly _free country_. I therefore conclude with my earnest prayer (the accomplishment of which the present state of the College does not allow us to doubt) ESTO PERPETUA.

THE DEDICATION.

TO THE STUDENTS AT THE NEW COLLEGE IN HACKNEY.

My young Friends,

Having drawn up the following _Heads of Lectures_ for your use, I take the liberty thus publickly to dedicate them to you; and as I earnestly wish for your improvement and happiness in all respects, excuse me if I take the farther liberty of making a few observations, and giving you some advice, of a more general nature, adapted to your age and circ.u.mstances.

As you will soon leave this place of education, and enter upon your several professions and employments, I hope your conduct will demonstrate to the world the solid advantages of this inst.i.tution, and that the great expence attending it, and the best attention of the managers, have not been bestowed in vain.

Many liberal friends of science, of virtue, and of religion, have contributed to procure you the advantages which you enjoy. They have spared no pains to provide able and careful tutors, and you have had every other advantage for the prosecution of your studies that they could procure you, unclogged by any subscription to articles of faith, or obligation of any other kind, besides such as they have deemed necessary for your own good, and to give the inst.i.tution its greatest effect. This is an advantage you could not have found elsewhere, at least in this country. And in every seminary of education much more depends upon opportunity for study, free from any obstruction, and undue bias, than upon the ability of tutors; though there is an additional advantage when they are able men, and eminent in the branches of science which they undertake to teach. But this is by no means so essential as many other circ.u.mstances.

Whatever be the qualifications of your tutors, your improvement must chiefly depend upon yourselves. They cannot _think_ or _labour_ for you. They can only put you in the best way of thinking and labouring for yourselves. If, therefore, you get knowledge, you must acquire it by your own industry. You must form all conclusions, and all maxims, for yourselves, from premises and _data_ collected, and considered by yourselves. And it is the great object of this inst.i.tution to remove every bias the mind can lie under, and give the greatest scope to true freedom of thinking and inquiry. And provided you be intelligent and virtuous men, and good citizens, it will be no cause of regret to the friends of this inst.i.tution, if, with respect to _religion_, or _politics_, you adopt systems of principles, and maxims of conduct, very different from theirs.

Give me leave, now that I am addressing you as _young men_, and young _students_, to suggest a caution on a subject, of the importance of which it is hardly possible that you should be sufficiently aware, because it is only impressed by that _experience_ which you have not yet had. I mean that degree of vanity which generally accompanies the acquirements that diligent persons of your age make in places of liberal education, and the contempt they are too apt to entertain for those who have not made the same proficiency with themselves. And I a.s.sure you, that in the observations I shall make on this subject, I have no view whatever to any thing that I have observed, or heard, of any of you in particular. But I have been in your situation myself, and I know the importance of these observations to students in general.

You are now at an age in which young persons usually make the most sensible advances in knowledge, and in which the understanding appears to ripen the most rapid manner. You are able to say every year, every month, and almost every day, what particular advances you have made, and how much you know more than you did before. And being taught, and accustomed, to express your thoughts in writing, you find yourselves qualified to do this in a manner of which you had no idea, or expectation, but a little time ago. You also perfectly remember what you have so recently learned, and many respects may be more particular and exact than even your tutors themselves.

The almost unavoidable effect of this is a high idea of your own powers and attainments, and too often a proportionable contempt of those who, not having had equal advantages, cannot do what you are easily capable of. A certain degree of vanity is, therefore, excusable in young persons; and, indeed, it is by means of it that they are excited to exert themselves in a manner that they would not otherwise have done.

But be careful that this temper be not indulged to excess, for it will then be found to have serious ill consequences; the least of which is the precluding future improvement, from being already satisfied with yourselves, and conscious of a sufficient superiority over others.

The foundation of this self-conceit, on account of literary attainments, will be found to be extremely weak. In fact, we learn more before the period to which you are now arrived, and I hope you will continue to learn more after it, without its being so much noticed; and the _ability_ that is discovered in the acquirements which are the subjects of this vanity is not greater than appears on other occasions. Only they are not so conspicuous.

What we all learn in the first three years of our lives, is much more extraordinary in its nature than all that we acquire afterwards. I mean the perfect use of our limbs, and the elements of speech. What we learn in a month in that early period of life, could not, if we were brought up in the ignorance of it, be learned in a year at any subsequent period. But these acquirements being universal, and what the circ.u.mstances in which we are all necessarily in compel us to learn, it does not appear extraordinary in any particular individual. Also, the proficiency that boys make at a grammar school, in which, in general, the dead languages only are taught (a knowledge of which is commonly the result of severe application) is too common to be the cause of much self-conceit. But the advances that are made at places of liberal education are both less common, and of a more conspicuous nature.

You will also find, if you continue your application to study, that it is only the elements of science that you can acquire here, and that if you live many years, they will bear but a small proportion to your future acquirements. But those future acquirements, in consequence of their bearing a less proportion to your whole stock of knowledge, will not be so conspicuous. Thus, though all the buildings that in one year are added to such a city as London would make a pretty large country town, they bear so small a proportion to what was built before, that they are not much noticed; whereas, had half the quant.i.ty of building been erected in a place where no house had existed before, it would have been a memorable event in the history of the country.

Also, as in old cities many buildings will fall to decay, while new ones are added; you must expect to forget much of what you now know. No man can give equal attention to every object; and as we advance in life, we, in general, only learn new things at the expence of the old ones.

But then they are the more valuable articles of knowledge, the more general and leading principles, which remain with us; while the more useless ones, things to which we give less attention because we find them to be of less use, disappear. Yet it is no uncommon thing for ingenious students to despise old scholars who are not so ready in the _minutiae_ of literature, though they may have forgotten more than those youths ever knew, and may retain what they cannot acquire without forgetting as much.

Another observation proper to lessen the conceit of literary men, is, that genius is not confined to _them_, but is equally great, though not equally conspicuous, in every other line of life, and especially in manufactures and the arts. Here, however, discoveries equal, with respect to _sagacity_, to those of Newton, contribute little to posthumous fame, because the discoverers are not writers.

But the greatest branch of intellectual excellence with respect to which every other is nothing, and which, from its nature, can never be foundation of any self-conceit, is _virtue_, or right dispositions of mind, leading to right conduct in life. Proper sentiments, and just affections of mind, arise from just, and often comprehensive, views of things, past, present, and to come. And if the real greatness of any thought, or action, be estimated by the number of elements that const.i.tute it, and its remoteness from the dictates of sense and natural appet.i.te, a virtuous and pious man will appear to be a much more dignified character, more proper to be viewed with admiration and esteem, than the greatest scholar; discovering, in fact, greater comprehension and force of mind. I mean, however, that virtue which is the result of reflection, of discipline, and much voluntary exertion, which, though operating with equal promptness and facility, is as much superior to mere _innocence_, and what is commonly called _good nature_, as motions secondarily automative are to those that are primarily so; a comparison which you who have studied _Hartley's Theory of the Mind_ will see the force of.

These considerations I take the liberty to suggest, as being proper to lessen that vanity which is so incident to those who distinguish themselves in the fields of literature, and which, operating like the acquisition of riches, or power, or any possession that is _rare_ among men, instead of enlarging, may tend to contract the mind, by confining its attention to itself. Beginning with a generous emulation, it proceeds to envy and jealousy, and ends in actual hatred and malignity, against which you cannot, surely, be too strongly put upon your guard; this being the greatest depravity to which human nature is subject, and which yet, like any other vice, may be in full possession of the mind, without the person himself knowing, or suspecting it; unless he give more attention to his feelings than most persons do. If no man ever thought himself to be avaricious, or cruel, can it be expected that any person should ever discover that he is too self-conceited?

Better, however, infinitely better, were it to rank with the merest dunces, than have the conceit and malignity (produced originally from conceit) of some who have distinguished themselves the most as linguists, critics, and poets. Even the study of nature, though, from its vast extent, it is less apt to produce this baneful effect, is not always a sufficient guard against it. This is an affecting and an alarming consideration. But in the intellectual, as in the civil and commercial world, we gain nothing but at the risk of some loss; and in this case the possible gain is worth the risk of even this great loss.

For when literary, and scientific excellence coincide with that which is of a moral nature, it adds unspeakably to the value of a character.

Ingenuity coupled with modesty, and great genius with benevolence and true piety, const.i.tute the perfection of human character, and is what we should ever have in view. And a course of education in which both these objects are equally attended to, is the only one that deserves to be called _liberal_: but such as, I hope, you have found this to be.

Give me leave further to observe to you, that the time that you spend in a place of liberal education is of more importance to you than you can be at present aware of. Whatever be the sphere of life for which you are destined, the probability is, that you will hereafter have but little leisure for reading and studying, compared to what you have now.

Besides, general maxims of all kinds, such as are the foundation of all our future conduct, in morals, religion, or politics, are generally formed at your time of life. From this period expect no great change in your opinions, or conduct; because now it is that you give particular attention to the forming your opinions on all subjects of importance; so that very little that is materially new to you can be expected to occur to you in future life, and almost every thing that you would choose to read will only tend to confirm you in the general principles that you will now adopt. There are, no doubt, exceptions to this, as well as every other general observation; but it is wisdom to suppose, and to act upon the supposition, that we are const.i.tuted as the generality of mankind are, and that we shall feel, and act, as they do. Since, then, so much depends on the leading principles and maxims which you will now adopt, be it your care to form just and good ones, and let no authority of tutors, or others, have any undue influence over you. In all cases think and judge for yourselves, and especially on all subjects of importance, and with as much attention as you can give to them.

It may not be amiss, in the present state of things, to say something respecting another subject, which now commands universal attention. You cannot but be apprised, that many persons entertain a prejudice against this College, on account of the republican, and, as they choose to call them, the licentious, principles of government, which are supposed to be taught here. Show, then, by your general conversation, and conduct, that you are the friends of peace and good order; and that, whatever may be your opinions with respect to the best form of government for people who have no previous prejudices or habits, you will do every thing in your power for the preservation of that form of it which the generality of your countrymen approve, and under which you live, which is all that can be reasonably expected of any subject. As it is not necessary that every good son should think his parent the wisest and best man in the world, but it is thought sufficient if the son pay due respect and obedience to his parent; so neither is it to be expected that every man should be of opinion that the form of government under which he happens to be born is the best of all possible forms of government. It is enough that he submit to it, and that he make no attempt to bring about any change, except by fair reasoning, and endeavouring to convince his countrymen, that it is in their power to better their condition in that respect, as well as in any other. Think, therefore, speak, and write, with the greatest freedom on the subject of government, particular or general, as well as on any other that may come before you. It can only be avowed tyranny that would prevent this. But at the same time submit yourselves, and promote submission in others, to that form of government which you find to be most approved, in this country, which at present unquestionably is that by _King, Lords, and Commons_.

As to _religion_, we may, surely, be allowed to think and act entirely for ourselves; in all cases obeying G.o.d and conscience rather than man.

But let us be thankful for the degree of liberty that we are allowed, though it be not all that we are justly ent.i.tled to; and let us not use any other means than reason and argument in order to better our condition. By this peaceable and steady conduct we shall at length convince those who will hear reason, that we are ent.i.tled to greater consideration; and doubt not but whatever is _true_ and _right_, will finally prevail, and be universally established.

That any of your tutors, or any of the friends of this inst.i.tution, wish to promote reformation, in church or state, by any other means than those of reason, and argument, is a _calumny_, utterly void of foundation, or probability. But your conduct, dispersed as you will soon be in different parts of the country, will be the best means of refuting it. Let us leave the method of proceeding by _riot_ and _tumult_ to those persons to whose schemes such proceedings are congenial. Truth stands in no need of such support, and will always triumph when a.s.sailed by such weapons. In return, then, for the advantages which you have enjoyed in this inst.i.tution, do it this service; and in recommending it, I trust you are doing substantial service to the cause of liberty and truth; and conferring a most important benefit on your country, and on mankind.

CONTENTS.

LECTURE I.

_The Introduction_ 1

LECTURE II.

_Of the Properties of all Matter_ 9 _Of Aeriform Substances_ 13

LECTURE III.

_Of Atmospherical Air_ 15

LECTURE IV.

_Of Dephlogisticated Air_ 18 _Of Phlogisticated Air_ 20

LECTURE V.

_Of Inflammable Air_ 21

LECTURE VI.