and to digest into an easy method, an account of every real improvement or discovery in science, in such a manner as shall enable the philosophers of the present age to resume and pursue the inquiries of their predecessors to the greatest advantage.

To

At the close of each part of the history I shall endeavour to give a comprehensive view of the discoveries which have been made in that branch of science to which it is appropriated, pointing out their natural connexion, noting what I shall imagine to be the principal desiderata, and giving hints for the extension of it. each volume I shall also subjoin an explanation of all the technical terms that occur in it; and, in order to give a clearer view of the progress of the science, I shall, whenever it can be done conveniently, exhibit a view of all those persons who have made the greatest figure in the history, after the manner of my "Chart of Biography.'

That my reader may the more easily satisfy himself from the fountain head with respect to any article, concerning which he may wish to have fuller information than I have given him, I have always been careful to refer, at the bottom of the page, to the very authors that I have made use of in compiling the work. Neither in this volume, nor in "The History of Electricity," shall 1 be found to have made a parade of quoting any author that I have not actually consulted. If I have met with any historical account of discoveries that I have reason to depend upon, I was glad to avail myself of such assistance; but the reader will always perceive when I have done so; and with respect to no fact of consequence have I contented myself with a second-hand account, if it was possible for me to come at the original, being truly conscious to myself that I have never spared any labour when I have thought that it would contribute to the real value of my work.

In some cases I have found historical accounts of experiments and discoveries so full and so well digested, that when I have afterwards met with the original, I have seen no reason to make any alteration. In this case I have generally let the_first_reference stand, because it pointed to the account which I had actually copied or abridged; but if I afterwards collected any additional circumstance from the original writer, I have sometimes quoted both; but in general I have found the accounts of discoveries and experiments given by subsequent writers, and even those of the greatest reputation, to be exceedingly lame and superficial; so that after I met with the original authors, I have been obliged to cancel the whole of the account which I had before drawn up.

As to the figures which I have made use of, especially those which relate to the elementary part of the work, I have not scrupled to make free with those of any writer that happened to suit my purpose. Most of them will be found in Smith, Muschenbraeck, and Rowning.

If I be so happy as to give my philosophical readers reasonable satisfaction with respect to the execution of this volume,* I think I may venture to promise them that, as I shall not fail to use the

* Divided into two parts.

same care and attention, they will have no less reason to be satisfied with the remaining volumes, as I am pretty confident that the subject of this volume is, on several accounts, attended with more difficulty than that of any other that is yet to come before me. At the same time, I imagine that it is of such a nature, that the history of it may be expected to be as generally entertaining as that of any other within the whole compass of philosophy.

This part of my work will exhibit a number of the finest gradations in the discoveries of different persons, a view of the greatest and happiest exertion of human genius, and the labours of those who are the most celebrated for their philosophical pursuits. The appearances in nature which these discoveries explain are constantly before our eyes, and must be perpetually exciting the curiosity of all thinking persons; the instruments, to the construction of which they led, are in daily use; and every thing relating to optics is capable of the more perfect illustration by figures.

For a variety of general observations on the subject of experimental philosophy, respecting the pleasure and advantage resulting from the study, I must refer to the preface to my History of Elec

* Which never appeared.

+ On these "gradations in discoveries," and their probable important results, I cannot forbear to quote, from Sect. i. of Period ii., at the beginning, the following paragraphs:

"From the origin of philosophy among the Greeks, to the commencement of the period I am now entering upon, (from the revival of letters in Europe, to the discoveries of Snellius and Descartes,) there were no less than two thousand years. In this long interval there was never any failure of persons who gave attention to the business of philosophy, though some portions of the time were more fruitful of this kind of literature than others; and the observation of the phenomena of nature, and the investigation of its powers, always held a considerable rank in the esteem of men of letters; and yet, though I have endeavoured to make the most of what remains concerning the knowledge of optics within this period, collecting from all nations indiscriminately, the reader has seen to how little it amounts. Some important observations did not, and indeed could not, well escape the notice of the ancients, and consequently we have seen a foundation laid for some useful branches of the system of optics; but we have hardly seen one just idea concerning the cause of any appearance, nothing of the true philosophy of light or vision. Though spectacles were invented towards the close of the above-mentioned period, and used by philosophers as much as others, it was some centuries before any satisfactory account was given of their nature and effects.

"To those who consider the world as having now arrived at its state of perfect manhood, with respect to science, two thousand years must appear a very disproportionate term of infancy; but he who considers that no bounds can be set to our advances in this kind of knowledge, (since the works of God are, like their Author, infinite,) that every new discovery is but an opening to several more, and consequently that the progress of real knowledge may be expected to go on, not merely in an uniform manner, but to be constantly accelerated; and who shall refiect upon the astonishing improvements that have been made in this branch, and indeed in all the branches of real knowledge, in little more than two centuries that have elapsed since the expiration of that long period of darkness-cannot help forming the most glorious expectations. He will be looking for new light and new satisfaction every day; and considering what has been done in very late years, together with the increasing avidity with which the study of nature is now pursued, and the greater numbers in all parts of Europe and America who are applying themselves to it, he may be almost assured that he will not be disappointed, provided the sources of information be easily open to him." History, pp. 29–31.

tricity, which may be considered as the first volume of the work which I am now carrying on.

In the last of my printed proposals I hinted that, in the next place, I should probably undertake the history of Magnetism; but having been lately engaged in a course of experiments relating to AIR, especially with respect to vegetation and respiration, and given more particular attention to those kinds which are noxious, (as that which is commonly called fixed air, the several species of inflammable air, that which is affected with the breath of animals, or putrid matter, &c.,) and as these experiments have terminated in several original observations, some of which I flatter myself will be thought curious and important, I now think that I shall next apply to the history of discoveries relating to AIR: but I propose to wait some time before I proceed with this work, that I may have an opportunity of judging whether it be agreeable to the public that I continue it or not.*

No. XXII.

DEDICATION AND PREFACE TO "EXPERIMENTS AND OBSERVATIONS ON DIFFERENT KINDS OF AIR, AND OTHER BRANCHES OF NATURAL PHILOSOPHY CONNECTED WITH THE SUBJECT. IN THREE VOLUMES; BEING THE FORMER SIX ABRIDGED AND METHODIZED, WITH MANY ADDITIONS."+ Birmingham, 1790.

Dedication.

To His Royal Highness GEORGE PRINCE OF WALES.‡ SIR,

IN dedicating this work to your ROYAL HIGHNESS, I express my own earnest wish, and that of many others, that to your other excellent qualities,§ your ROYAL HIGHNESS may add a disposition to patronize a branch of science, in the extension of which the natives of Great Britain have ever borne a distinguished part, and which has for its object the benefit of all mankind.

It is by increasing our knowledge of nature, and by this alone, that we acquire the great art of commanding it, of availing ourselves of its powers, and applying them to our own purposes; true science being the only foundation of all those arts of life, whether

It was discontinued for want of encouragement. Thus, writing to Dr. Price from "Leeds, Sept. 27, 1772," the Author says, "As to the History of Experimental Philosophy, it does not appear, from Mr. Johnson's last account of the sale of my History of Vision, &c., that it will be worth my while to prosecute it any further."

With the following motto from "the first of the six volumes :"

Fert animus causas tantarum expromere rerum,
Immensumque aperitur opus.

Prince Regent, 1810; George IV. 1820-1830.
Estimated, no doubt, by favourable observers.

LUCAN,

relating to peace or war, which distinguish civilized nations from those which we term barbarous; a distinction not less conspicuous than that between some nations of men and some species of brutes. And that branch of this great science to which the subject of this work relates, viz., chemistry, is perhaps of more various and extensive use than any other part of natural knowledge; and by the application that is now given to it, it is continually growing in relative magnitude and importance.

In the age of Newton, chemistry was but little cultivated; and its value not being generally known, it was not regularly taught in places of liberal education, in which natural philosophy was always more or less attended to; whereas, at present, every thing that is not denominated chemistry, is but a small part of a system of natural knowledge. It is no less remarkable that the doctrine of air, of which little or nothing was known in the time of Newton, and which, a few years ago, was hardly mentioned in the writings of chemists, now makes a very considerable figure in the mass of chemical knowledge, and throws the greatest light on the most important processes.

It is, therefore, earnestly to be wished that this branch of natural science should be assiduously cultivated, and the patronage of princes may be eminently useful to this end, by diffusing a taste for it among those whose opulence will enable them to prosecute it to the most advantage.

It is true that we are indebted to the poverty of many persons for some of the most simple and effectual modes of operating in chemistry, necessity having in this, as well as in many other cases, been the happy mother of invention. But in some cases it is well known that the most promising projects have become abortive for want of the means that were necessary to carry them into execution; for in this science mere observation and reflection will not carry a man far. He will frequently have occasion to put the substances which he examines into various new situations, and observe the result of circumstances, which, without expense, as well as labour, he can have no opportunity of knowing.

Hence it is that the greatest and happiest effects may be expected from the patronage of science by persons of your ROYAL HIGHNESS's rank and expectations, whose wishes and inclinations are often alone sufficient to give a turn to the taste and pursuits of the rich and great; and hitherto almost every country in Europe can boast of more persons among their nobility and men of fortune who are devoted to scientifical pursuits, than Great Britain.

It will perhaps be said, that men of high rank and fortune in this country are occupied about the greater objects of civil policy, and attending to the interests and liberties of the nation: but, admitting this to be the case of all, which is evidently that of a small number only, no one object wholly engages the attention of any man. All men have their pleasures as well as their business, nor is it desirable that any one object should so much engross any person as that he should give no degree of attention to any other; and no pursuit can have a juster claim to the leisure hours of men of rank and fortune

than that of natural science, since, independently of any views of utility, none can furnish more rational amusement.

Permit us, then, who are engaged in the quiet pursuits of philosophy, to flatter ourselves that they will have the additional recommendation of so effectual a patronage as that of your ROYAL HIGHNESS; and I am persuaded that your ROYAL HIGHNESS does not need to be reminded, that the greatest princes have been the protectors of science and of letters, and that they have ever considered this patronage as reflecting lustre on their crowns.

In some countries the sciences seem to require the support of princes, or of the community, by pensions and establishments. In ours, these aids are unnecessary. Our Royal Society, which gives none but honorary rewards, is all that is wanted in the way of establishment; and it has been, and is, eminently useful. In this country, patronage is not wanted for those who cultivate the sciences, but rather for the sciences themselves; to give them their due value and consideration, to apply the influence which the great possess over the minds and opinions of men, in directing their tastes to useful pursuits, and thus to incite a sufficient number of able inquirers to explore the hidden powers which the Deity has impressed on matter.

Considering your ROYAL HIGHNESS as destined to be the future sovereign of this country, I cannot wish you greater glory or happiness than that you should consider it as consisting, not in the extent, but in the flourishing state, of your dominions, to which science, manufactures, and commerce (each the true source of the other), will most eminently contribute; and that you should not be dazzled by the flattering, but often fatal, idea of extending what is called the royal prerogative; but rather study to give your subjects every power which they can exercise for their own advantage. And whatever flatterers may suggest, the people (each of them giving his whole attention to those things in which he is most interested) will always be able to do more for themselves than the most enlightened and best disposed princes can do for them.

As a person whose deliberate judgment has led him to dissent from the mode of religion by law established in this country, permit me, Sir, to express something more than a wish that, as the future sovereign of Great Britain, you will be the equal father of all your subjects, and that in your reign every man will meet with encouragement and favour in proportion to the services he renders his country, and the credit he is to it.

There has of late years been a wonderful concurrence of circumstances tending to expand the human mind, to shew the inconvenience attending all establishments, civil or religious, formed in times of ignorance, and to urge the reformation of them. Let these be suffered to operate without obstruction, and have the true magnanimity to let no impediment be thrown in the way of the efforts of the more enlightened part of the community to improve the state of it in any respect.

A sovereign conducting himself by these liberal maxims will rank among the few truly great and good princes whose object has