Chapter VII: Part 7

[49] See also the 1st, vol. of his early edition of experiments on air p. 29.

Numerous indeed those experiments were as well as important: far too numerous to be particularised here; though it may not be improper to call to the recollection of the reader some of the more interesting facts which we owe to Dr. Priestley, and the times of their discovery and communication.

The first of his _publications_ on pneumatic chemistry was in 1772, announcing the method of impregnating water with fixed air, and on the preparation and medicinal uses of artificial mineral waters; a discovery that domesticated much of the knowledge that had heretofore been disclosed only in the works of learned societies; and that beautifully exemplified how much of the health and the pleasure of common life, might depend on the ingenious researches of men of science. Though this was the first publication of Dr. Priestley on the chemistry of the airs, he had certainly commenced his experiments in this branch of Science, soon after his arrival at Leeds, and as early at least, as 1768. In the year 1771 he had already procured good air from saltpetre; he had ascertained the use of agitation, and of vegitation as the means employed by nature in purifying the atmosphere destined to the support of animal life, and that air vitiated by animal respiration was a pabulum to vegetable life; he had procured factitious air in a much greater variety of ways than had been known before, and he had been in the habit of substituting quicksilver in lieu of water, for the purpose of many of his experiments. In his paper before the Royal Society, in the spring of 1772, which deservedly obtained him the honour of the Copley Medal, he gives an account of these discoveries. In the same paper he announces the discovery of that singular fluid nitrous air,[50] and its beautiful application as a test of the purity or fitness for respiration of airs generally. In the same paper he shews the use of a burning lens in pneumatic experiments, he relates the discovery and properties of marine acid air; he adds much to the little of what had been heretofore known of the airs generated by putrefactive processes, and by vegetable fermentations, and he determines many facts relating to the diminution and deterioration of air, by the combustion of Charcoal, and the calcination of metals.

[50] Honestly referring to Dr. Hales and Mr. Cavendish for any idea that might have remotely led to this discovery (See Obs. on air 1st ed. v. 1 p. 108) the discovery however was completely his own.

Dr. Priestley seems always to have thought nitrous air as convenient a substance for eudiometrical experiments as any of the later substitutes, viz. the liquid sulphurets and the combustion of phosphorus. The foundation of Mr. Davy’s substitute, muriat or sulphat of iron saturated with nitrous air, was as Mr. Davy acknowledges first discovered by Dr. Priestley himself. See Nich. Journ. for Jan. 1802 p. 41. The different states of the solutions of iron in vitriolic acid have been ingeniously applied to the analysis of mixed gasses by Humboldt and Vauquelin.

Soon after this, in confirmation of Sir John Pringle’s theory of intermittents and low fevers being generally owing to moist miasma when people are exposed to its influence, he ascertained by means of his nitrous test that the air of marshes was inferior in purity to the common air of the atmosphere.[51]

He had obtained very good air from saltpetre in 1771, but his full discovery of dephlogisticated air, seems not to have been made until June or July, 1774,[52] when he procured it from precipitate per se, and from red lead. This was publicly mentioned by him at the table of Mr. and Madame Lavoisier, at Paris, in October 1774, to whom the phenomena were until then unknown. The experiments on the production of dephlogisticated air, he made before the scientific chemists at Paris about the same time, at Mr. Trudaine’s. This hitherto secret source of animal life and animal heat, of which Mayow had but a faint and conjectural glimpse, was certainly first exhibited by Dr. Priestley, and about the same time, (unknown to each other) by Mr. Scheele of Sweden. For the honour of science, it were much to be wished that the pretensions of Mr. Lavoisier were equally well founded. He has done sufficient and been praised sufficiently for what he has done, to satisfy a mind the most avaricious of fame; he is deservedly placed in the first rank among the philosophers of his day, and he ought not to have thrown a shade over his well earned reputation, by claiming for himself the honour of those discoveries which he had learned from another.

[51] Phil. trans. v. 54 p. 92.

[52] See Doctrine of Phlog. established p. 119.

From this brief account of the first stage of Dr. Priestley’s chemical labours, it appears that during the short period of two years, he announced to the world more facts of real importance, and extensive application, and more enlarged and extensive views of the œconomy of nature, than all his predecessors in pneumatic Chemistry had made known before.

In 1776 his observations on respiration were read before the Royal Society; in which he clearly discovered that the common air inspired, was diminished in quantity, and deteriorated in quality, by the action of the blood on it _through the blood vessels of the lungs_; and that the florid red colour of arterial blood, was communicated by the contact of air through the containing vessels. His experiments on the change of colour in blood confined in a bladder, took away all doubt of the probability of this mode of action. I cannot help thinking that the circumstance of Dr. Priestley’s mind being so much occupied with the prevailing theory of Phlogiston, was the reason why he did not observe that the diminution of the air, and the florid colour of the arterial blood was owing to the absorption of the pure part of the atmosphere, _rather_ than to any thing emitted from the blood itself. This part of the theory of respiration Mr. Lavoisier has certainly established; though it is by no means ascertained as yet whether the vital part of the atmosphere inspired, is wholly and alone absorbed, or whether in reality something is not contributed in the lungs to the formation of the fixed air found after expiration.[53]

[53] That azote is absorbed during respiration as Dr. Priestley supposed contrary to Mr. Lavoisier’s opinion, is made extremely probable by the experiments of Mr. Davy, whose accuracy is well known. Researches, p. 434. The formation of water in this process, is certainly no more than conjecture as yet. Dr. Bostock has lately published a very useful and laborious history of discoveries relating to respiration, both anatomical and pneumatical.

In 1778 Dr. Priestley pursued his experiments on the property of vegetables growing in the light to correct impure air, and the use of vegetation in this part of the œconomy of nature. A discovery which was announced to several men of science in England previous to the publication of the same ideas by Dr. Ingenhouz.[54] Indeed from its having been communicated to M. Magellan whose pleasure and whose occupation it was, to give information of new facts to his philosophical correspondents, and of this in particular to Dr. Ingenhouz then engaged in similar researches, there is hardly a doubt but the latter knew of the experiments then pending on the subject by Dr. Priestley.

[54] Doctrine of Phlogiston established, p. 107, et. seq. The theory of the amelioration of impure air by the absorption and excretion of vegetables growing in the light, has been doubted by Dr. Darwin in his Phytologia, and opposed by Count Rumford in a paper published in the transactions of the Royal Society, for 1787: also by Dr. Woodhouse of Philadelphia, Nicholson’s Journal, for July 1802, and by Mr. Robert Harrup, Nicholson’s Journal, for July 1803.

It is painful to notice these aberrations from propriety in the conduct of men highly respectable in the philosophical world, arising from an over anxious avarice of literary fame, and an improper jealousy of the reputation of another. Not that it derogates from the character of a philosopher to wish for the applause of those who know how to appreciate his merit, or who are benefited by his exertions; such an anxiety is laudable when it does not lead to encroachments on the literary rights of others; nor is it at all desireable under the present circumstances of human nature, to expect from men of science an attention to their pursuits arising from motives of pure benevolence alone, and excluding all views, hopes, and expectations of the gratifying tribute of public approbation. I believe no man ever laboured with a more single eye to public utility than Dr. Priestley. But consideration in society, and the respectability attendant upon great talents, and great industry, successfully employed for the benefit of mankind, is a motive to useful exertion so universal, so honest, so laudable, and withal so powerful, that it is the common interest, as well as the duty of society, to bestow it liberally where it has been earned faithfully, and to concede it to those only, who have really deserved this honourable reward.

From this period Dr. Priestley seems to have attended to his pneumatic experiments as an occupation; devoting to them a regular portion of his time. To this attention, among a prodigious variety of facts tending to shew the various substances from which the gasses may be procured; the methods of producing them; their influence on each other, and their probable composition, we owe the discovery of vitriolic acid air, of fluor acid air, of vegetable acid air, of alkaline air, and of dephlogisticated nitrous air, or gazeous oxide of azote as it has been called, the subject of so many curious experiments by Mr. Davy. To these we may add the production of the various kinds of inflammable air by numerous processes that had escaped the observation of Mr. Cavendish; in particular the formation of it by the electric spark taken in oils, in spirits of wine and in alkaline air; the method of procuring it by passing steam through hot iron filings, and the phenomena of that hitherto undetermined substance the finery cinder, and its alliance to steel. To Dr. Priestley we owe the very fine experiment of reviving metallic calces in inflammable air and its absorption in toto, apparently at least, undecomposed. He first ascertained the necessity of water to the formation of the gasses, and the endless production of air from water itself.

Dr. Priestley’s experiments on this subject, to wit: the generation of air from water, opened a new field for reflection, and deserves more minute notice. No theory has yet been proposed adequate to the explanation of the facts. He had before remarked that water was necessary to the generation of every species of air, but the unceasing product of air from water had never been before observed.

In his first set of experiments he procured air, by converting the whole of a quantity of water into steam: then, to obviate the objection to the water having imbibed air from the atmosphere he put the water on mercury in long glass tubes immersed in mercury: in a third process he used no heat, but merely took off the pressure of the atmosphere. In all these cases a bubble of air was extricated from the water, which being separated by inclining the tube, another bubble was again produced on each repetition of the experiment. That this could not be air imbibed from the atmosphere appeared from this, that though the first portions were generally purer than atmospheric air, the next became less pure, and at length wholly phlogisticated.

It did not appear that the addition of acids, enabled the water to yield more air, nor did he succeed in attempting to convert the whole of a given quantity of water into air, although exposing the water confined over mercury to heat, and separating the air produced, it still continued to produce more air for twenty or thirty repetitions of the experiments. When a certain proportion of air was thus produced at any one time, no continuance of the experiment would encrease the quantity until it was separated. Hence he concludes that the longest continuance of water in the state of vapour would not convert it into air. The water used was pure distilled water previously boiled to separate any adventitious air that might have been imbibed from the atmosphere. The precautions he used, and the replies to such objections as he foresaw the experiment would be liable to, are detailed in the papers he published on the subject, to wit, a separate pamphlet published in England in 1793, and a communication in the Am. Ph. trans, v. IV. p. 11-20.

In the last mentioned paper, he proceeds also to give an account of some experiments on the property of water to imbibe different kinds of air, and the conversion of sp. of wine, into inflammable air.

This paper inserted in the American transactions, was read before that society in Feb. 1796. In Ap. 1800 another paper was read before the same society on the production of air by the freezing of water Am. Ph. trans. v. V. p. 36. In this paper he recapitulates the general result of his former experiments on the generation of air from water, namely “that after all air had been extracted from any quantity of water by heat or by taking off the pressure of the atmosphere, whenever any portion of it was converted into vapour, a bubble of permanent air was formed, and this was always phlogisticated. The process with the Torricellian vacuum (he says) I continued for some years and found the production of air equable to the last. The necessary inference from this experiment is, that water is convertible into phlogisticated air, or that it contains more of this air intimately combined with it than can be extricated from these processes in any reasonable time.”

He proceeds to state his imperfect attempts to procure air from water by freezing, until he procured cylindrical iron vessels seven or eight inches high and near three inches wide at the bottom, the upper orifice closed with a cork and cement, in the centre of which was a glass tube about one fifteenth of an inch in diameter. In this apparatus the water in the iron vessel was frozen by means of snow and salt, the vessel being immersed in mercury, and the water contained over the mercury. The quantity of water was about three ounces. The experiment was repeated nine times without changing the water, and the last portion of air procured in this manner was as great as any of the preceding; so that there remained no reasonable doubt but that air might be produced from the same water in this manner ad libitum. Having obtained near two inches of air in the glass tube, Dr. Priestley put an end to the experiment, and examining the air found it wholly phlogisticated, not being affected by nitrous air, and having nothing inflammable in it.

The inference drawn by the Doctor from those experiments is, that water when reduced by _any means_ into the state of vapour, is in part converted into phlogisticated air; and this is one of the methods provided by nature for keeping up the equilibrium of the atmosphere, as the influence of light on growing vegetables is the means of recruiting the other part; both of them being subject to absorption and diminution in several natural processes. And he thinks that they strengthen also the opinion, that water is the basis of every kind of air, instead of being itself a compound of hydrogen and oxygen according to the new theory. At all events the experiments themselves must be considered as extremely curious, as well as new.

The water and the salt thus made use of gave rise to another experiment of the most important nature to the present theory of chemistry, if it should on future repetition be ultimately verified. This experiment related by Dr. Priestley in a letter to Dr. Wiston is in substance as follows. Having repeatedly used as above mentioned a freezing mixture of common salt and snow, the experiment being finished, he evaporated the snow water in an iron vessel and recovered the salt. The salt thus recovered contained some calx of iron. He put it by in a bottle and labelled it, according to his usual practice. In October 1803, he wanted to procure some marine acid, and took the salt thus procured by evaporating the snow water, for the purpose. On commencing the distillation, he was surprized to find the receiver full of the characteristic red fumes of the nitrous acid. The vitriolic acid used for the purpose was diluted with about an equal quantity of water. On finishing the process, he took some of the acid in the receiver, and dissolved copper in it, and thus procured good nitrous air. He was himself perfectly persuaded that no nitre had been used in the freezing mixture, nor had any by accident or design been mixed with the salt. He was not unacquainted with the common mode of clearing black oil of vitriol by the addition of nitre. So that no means of accounting for this curious fact remained, but the snow or the iron: he seemed to think that should this experiment be fully verified hereafter, it would confirm the vulgar hypothesis of snow containing nitre, and account for the fertilizing quality usually attributed to snow. He had no opportunity in that winter of repeating the experiment as he died in about three months after, and his previous illness had compelled him to forsake his laboratory.

Of the almost discarded theory of Phlogiston Dr. Priestley to his death remained the strenuous advocate, and almost the sole supporter; _ipse Agmen_. Beautiful and elegant as the simplicity of the new doctrine appears, many facts yet remain to be explained, to which the old system will apply, and the French theory is inadequate. These are collected with an ingenuity of arrangement, and a force of reasoning in the last pamphlet published by the Doctor on the subject,[55] which no man as yet unprejudiced can peruse, without hesitating on the truth of the fashionable theory of the day.

[55] The doctrine of phlogiston established 1803.

Certainly, it has not yet been sufficiently explained on the new theory, what becomes of the Oxygen from the decomposed water in the solution of metals in acids; nor why inflammable air is produced when one metal in solution is precipitated by another; nor why dephlogisticated air is hardly to be procured from finery cinder, if at all; nor why this substance so abounding in oxygen according to the new theory, will not oxygenate the muriatic acid; nor why it should answer all the purposes of water in the production of inflammable air from charcoal; nor why water in abundance should be produced when finery cinder is heated in inflammable air, and none when red precipitate is exposed to the same process; nor what becomes of the oxygen of the decomposed water when steam is sent over red hot Zinc, and inflammable air is produced without any addition in weight to the Zinc employed; nor why there should be a copious production of inflammable air when hot filings of Zinc are added to hot mercury in a hot retort and exposed to a common furnace heat, which I believe is an unreported experiment of Mr. Kirwan’s; nor why sulphur and phosphorus are formed by heating their acids in inflammable air without our being able to detect the oxygen which on the new theory ought to be separated, nor why water should be produced by the combustion of inflammable air with ,47 of oxygen, and nitrous acid when ,51 of oxygen is employed, for this experiment can now no more be doubted than explained; nor why on the new doctrine the addition of phlogisticated air, should make no alteration in the quantity of acid thus obtained; nor why red hot charcoal slowly supplied with steam, should furnish inflammable air only and not fixed or carbonic acid air; nor why nothing but pure fixed air should be produced by heating the carbonated Barytes in the same way; nor why fixed air should be formed under circumstances when it cannot be pretended that Carbon is present, as when gold, silver, platina, copper, lead, tin and bismuth are heated by a lens in common air over lime water; or why the grey and yellow calces of lead should furnish carbonic acid and azote, and no oxygen; nor why the residuum of red lead when all its oxygen is driven off by heat should be either massicot or glass of lead according to the degree of heat, and not lead in its metalline state; nor why plumbago with steam should yield inflammable and not fixed air; nor why minium and precipitate per se heated in inflammable air should produce fixed air; nor why on the evaporation of a diamond in oxygen, the fixed air produced should far exceed the weight of the diamond employed, if some of the oxygen had not entered into the composition of the carbonic acid so formed; nor why there should be a constant residuum of phlogisticated air (or azote) after the firing of dephlogisticated and inflammable airs, if it be not formed in the process; nor why phlogisticated air if a simple substance, should be so evidently formed in the various processes enumerated by Dr. Priestley in the 13th section of the pamphlet of which I have made the foregoing abstract? whether the doctrine of phlogiston is still to be used as the key to the gate of chemical theory, or whether it be properly thrown aside for the elegant substitute of the French chemists, can hardly be ascertained, until the preceding difficulties are cleared up on the new doctrine, for on the old theory they are sufficiently explicable. The summary of arguments in favour of Phlogiston, published by Dr. Priestley, in 1803, are evidently too important, and too difficult of reply, to be slighted by those who adopt the opposite opinions. _Non nostri est tantas componere lites._ Should the old theory ultimately fall, it maybe fairly said of its respectable supporter, _si Pergama dextra defendi potuit, etiam hac defensa fuisset_.

This was almost the last of Dr. Priestley’s chemical publications,[56] through all which, his characteristic talent as an author has been eminently preserved, that of not only adding greatly to the existing stock of knowledge, but exciting others to exertion and reflection in the same line of pursuit. Nor can I help thinking that much of the labours of the French philosophers in this department of science would never have been undertaken, if they had not been called forth by the previous discoveries, not of Lemery, Margraaf, Bayen, Macquer, and Beaumè, but of Hales, Black, and Macbride; of Cavendish and Priestley and Scheele.[57] Would to God there were no other object of contest between the rival nations of Great Britain and France, but which should add most to the sum of human knowledge, and contribute most to the means of human happiness.

[56] To the end of this Appendix will be subjoined a list of the scattered papers on Philosophical subjects which Dr. Priestley published in periodical collections, besides those which are inserted in the Philosophical transactions.

[57] I do not mean to deny the tribute of praise to Marriotte and Venel, any more than to Brownrigg and Lane, and it is certain that Lavoisier was engaged in pneumatic experiments, previous to 1774.

It is impossible to conclude the preceding account better than by the following extract of a letter to Mr. Lindsey from a man[58] well able to appreciate the labours of Dr. Priestley; and the late testimony in favour of his discernment by Dr. Bostock. “To enumerate Dr. Priestley’s discoveries, would in fact be to enter into a detail of most of those that have been made within the last 15 years. How many invisible fluids whose existence evaded the sagacity of foregoing ages has he made known to us? The very air we breathe, he has taught us to analyze, to examine, to improve: a substance so little known, that even the precise effect of respiration was an enigma until he explained it. He first made known to us the proper food of vegetables, and in what the difference between these and animal substances consisted. To him Pharmacy is indebted for the method of making artificial mineral waters, as well as for a shorter method of preparing other medicines; metallurgy for more powerful and cheap solvents; and chemistry for such a variety of discoveries as it would be tedious to recite: discoveries which have new modelled that science, and drawn to it and to this country, the attention of all Europe. It is certain that since the year 1773, the eye and regards of all the learned bodies in Europe have been directed to this country by his means. In every philosophical treatise, his name is to be found, and in almost every page. They all own that most of their discoveries are due either to the repetition of his discoveries, or to the hints scattered through his works.”[59]

[58] Richard Kirwan, Esqr.

[59] Vindiciæ Priestlianæ, p. 68.

“This is not the only instance” (says Dr. Bostock,[60] speaking of Mr. Jurin’s opinion that azote was generated, instead of being absorbed, in the process of respiration as Dr. Priestley, and after him Mr. Davy had supposed,) “in which, after the conclusions of Dr. Priestley have been controverted by his contemporaries, a more accurate investigation of the question, has ultimately decided in his favour. The complicated apparatus, and imposing air of minuteness which characterize the operations of the French chemists, irresistibly engage the assent of the reader, and scarcely permit him to examine the stability of the foundation upon which the structure is erected. The simplicity of the processes employed by Dr. Priestley, the apparent ease with which his experiments were performed, and the unaffected conversational stile in which they are related have, on the contrary been mistaken for the effects of haste and inaccuracy. Something must also be ascribed to the theoretical language which pervades, and obscures the chemical writings of this Philosopher, in consequence of his unfortunate attachment to the doctrine of Phlogiston.”

[60] Essay on respiration, p. 208.

When the operose experiment of the French chemists on the formation of water, shall have been sufficiently repeated, and verified by other experiments to the same point, less complex, less tedious, less expensive, and easy to be repeated; when the water thus supposed to be formed is sufficiently distinguished from the water absolutely necessary to the generation of all airs, and attendant upon them[61] both in a state of mixture and combination; and when the difficulties enumerated a page or two back, as attendant on the modern theory shall be explained on the new system, as well as on that of Stahl, then, and not until then, will it be time to lament Dr. Priestley’s unfortunate attachment to the doctrine of Phlogiston.

[61] Mr. Kirwan found that common inflammable air from iron, and vitriolic-acid, contained about 2-3 of its weight of water mixed with it; which might be separated from the air by means of concentrated vitriolic-acid in a watch glass over mercury, without diminishing the quantity or altering the characteristic properties of the air thus treated.

_Of Dr. Priestley’s other Scientific Works._

The other philosophical labours of Dr. Priestley consist of his history of electricity, his history of the discoveries relating to light and colour, and his popular introductions to perspective, electricity and natural philosophy.

It appears that after the publication of his history of electricity, he intended to have pursued the plan, by composing similar histories of every branch of science: a magnificent idea, and which none but a man conscious of uncommon powers could have contemplated. Few men indeed were so capable of such an undertaking as Dr. Priestley; for independant of his habits of patient and regular industry in his literary pursuits, and the wide field of his attention to scientific objects, he had a facility of perusing, abstracting, and arranging the works of others, not commonly attendant even upon equal abilities in other respects. This great undertaking of Dr. Priestley to embrace the various departments of philosophy, appears a labour sufficient for one life; and had due encouragement been afforded, this projected series of histories would in all probability have been compleated, usefully to the world, and reputably to himself. But he proposed this undertaking laborious as it was, without designing that it should occupy the whole or the principal portion of his time, but his leisure hours only; for at no period did he postpone his professional duties, or his theological studies, to any other object whatever. The life of Dr. Priestley is almost a perpetual illustration of a seeming paradox, respecting mental energy, that men of talents, uncommonly laborious, and who appear to get through more business than one person could be supposed equal to, have usually more leisure time at their disposal, than those who have little to do: so much does the habit encrease the power of exertion. Nor was any man less averse to the innocent pleasures of social enjoyment than Dr. Priestley, or better calculated as well as more inclined to contribute to the common stock of amusing, and instructive conversation. It cannot indeed be truly said of him, as Dr. Johnson[62] once related of himself, that he had never refused an invitation to dinner on account of business but once in his life, yet no man more readily found leisure for social intercourse. This arose from his habit of dividing his time into certain portions appropriated to his respective pursuits, and determining to perform a certain quantity of literary duty, within the assigned period.

[62] On that day, (Dr. Johnson said) as it was an unusual deprivation, he found himself disinclined, and unable to attend steadily to the work that led him to refuse the invitation. He walked about his library occasionally looking over first one book and then another until about four o’clock when weary of staying within he went to a tavern to dine. Dr. Johnson had for a long time a dislike to Dr. Priestley who bore two of the characters most in disrepute with Dr. Johnson, that of a whig and a dissenter. Dr. Priestley’s pursuits also consisting so largely of heterodox theology, which Dr. Johnson abominated, and experimental philosophy which he heartily despised, they had hardly a common point of union. Toward the latter part of Johnson’s life, they met; and upon the friendly terms that ought to obtain between two men, who, each in their way, deserved so well of the republic of letters.

The first edition of his history of Electricity, was in 1767: it went through another edition in 1769, and a third in 1775. It was published at a very happy time, when electricity was a favourite object of attention to many respectable men of science then living, and it contributed in a great degree to turn the public attention toward the study of these phenomena. Very much of what has been done since may be fairly attributed to the popularity given to this branch of experimental philosophy by Dr. Priestley. Nor did he confine himself to a mere narration of the labours of others; the second volume contains many new experiments of his own, and some of them form very curious and important additions to the stock of electrical knowledge.[63] The discoveries of the last thirty years, particularly including those of Galvanic Electricity, are so numerous, and so dispersed in volumes difficult to be procured, that a continuation of this history is a desideratum in the scientific world; at one time there was an expectation of seeing it from the pen of Mr. Nicholson, whose general knowledge, and industry, as well as his attention to this branch of philosophy in particular, render him peculiarly qualified for the task. But the proposals he communicated to Dr. Priestley, on the subject, were not pursued to effect.[64]

[63] Dr. Priestley among his other experiments on electricity first ascertained the conducting power of charcoal and the calcination and vitrification even of the most perfect metals by the electric spark. He seems first to have used large batteries, which M. Van Marum and his associates have carried to such extent.

The solutions of the metals, the gasses produced and the circumstances which accelerate and prevent these effects in Galvanic processes with the pile of Volta, as detailed by Dr. Priestley in his paper on this subject in Nich. Journ. for March 1802 p. 198 form very important additions to the mass of knowledge respecting the Galvanic fluid. Nor are his discoveries in pneumatic electricity, of the conversion of oils, spirit of wine and the alkaline gass into inflammable air or hydrogen of less moment.

[64] Dr. Bostock, who seems to have many requisites to qualify him as the historian of particular branches of science, has published a good attempt toward the history of Galvanism in Nicholson’s Journal.

These histories of detached branches of Science, would not only be highly useful, but they may be considered as in some measure necessary to the accurate pursuit, and advancement of science itself. They are not only useful for the purpose of shewing the discoveries that have been made, and the time of their publication, the ideas that appear to have suggested them, the persons to whom we are indebted for them, and their effect on the spirit of enquiry at the time, but they prevent a man of science from being led into mistakes, from doing what has been already done, from suggesting what has been already published, and from ignorantly claiming to himself the merit due to the labours of a predecessor. Books are now so multiplied, in languages so various, obtained with so much difficulty, and at an expence so far exceeding the usual means of scientific men, that those who like Dr. Priestley fully and faithfully execute a work of this description are real benefactors to mankind.[65]

[65] The transactions of the various academies and philosophical societies in Europe amount at least to 1000 volumes in quarto. The royal society of England in 1665 led the way to similar institutions.

The history of ELECTRICITY was composed by Dr. Priestley in one year. The three editions of the work in less than eight or nine years sufficiently shew that, in the opinion of men of science, it was well composed: otherwise the celerity of its composition, would no doubt derogate from, instead of adding to, the well earned reputation of the author; and rather tend to shew that he was too careless or too conceited to take the necessary pains and employ the necessary time to make it fit for public inspection. Every man owes to the public, that if he professes to instruct them, he should dedicate as much labour as the subject demands, or at least as much time as it is in his power to devote to it. I fully accede to the ingenious correction of the _nonum prematur in Annum_, suggested by the witty Dr. Byrom of Manchester; but something of the _Limæ Labor_, respect for the tribunal of the public demands of every man who appears before them in the character of an author. Dr. Priestley has in more instances than one, been accused of unnecessary if not of culpable rapidity in his literary compositions: but he never professed to be a fine writer; he never sought after the beauties of stile; and his common language was sufficiently neat and expressive, to communicate the facts and the arguments upon which it was employed. It is also to be remarked, that the facility of composition which he acquired from long practice, made that labour light to him, which would have been too much for a less skilful and a less experienced composer. In many instances indeed of his rapid publications, he had not to _seek_ for arguments, but to express in his unornamented and unaffected manner, the ideas that forced themselves upon him relating to a subject previously considered and upon which he had long made up his mind.

The History of Discoveries respecting LIGHT and COLOURS published in 1772 was a more difficult task, nor did it meet with equal encouragement. Sir Isaac Newton’s important labours in this branch of science, could not be fully comprehended without a portion of mathematical knowledge not even then so common as formerly, among the philosophers of the day. Mathematical studies seem to have in themselves very little to interest, compared with other literary pursuits; although by long attention and habit, that interest may be excited and kept up. It was about this time that the popular phenomena of chemistry and electricity more decidedly took their stand in the field of science, and irresistably seized hold on the attention of the world: phenomena, highly amusing in themselves, strongly attractive from their novelty, of evident and immediate application, and that promised an incalculable harvest of honourable and useful discovery, to such as would become their votaries. Little had been done in this department of philosophy, little previous knowledge was required to comprehend all that was known, and those who were unable to read a page of Sir Isaac Newton with profit, could easily mix an acid and an alkali, or turn the wheel of an electrical apparatus.

By this time too, it had been discovered, that there were other powers in nature that must be called in to explain appearances, which the mechanical and corpuscular philosophy had endeavoured to elucidate in vain. Such were magnetism, electricity and chemistry. It began to be found out, that the science of calculation, was but an aukward handmaid to their sister branches of natural philosophy, while physiology, laughed outright at the clumsy addresses of her mathematical admirers, from Borelli to Keill.

The discoveries therefore relating to light and colours, at the time when Dr. Priestley proposed his history, being intimately associated with the study of the mathematics, and the profound investigations of Sir Isaac Newton, were out of the beat of the less laborious, but more fashionable philosophy of the day; and were not so generally interesting to the Sciolists and Amateurs. Hence the work in question, though treated in a very entertaining and popular manner, and by no means crouded with reference to Diagrams or abstruse discussions, was not popular even among that class of readers, who might reasonably be calculated on, as the purchasers of such a performance. The subscribers indeed were sufficiently numerous, and respectable, but by far the majority were defaulters in respect of payment. It did not pay the bookseller: and of course still less did it recompence Dr. Priestley in a pecuniary point of view, especially as he had gone to considerable expence with a view to the completion of his extended plan. To him indeed, though pecuniary loss was a serious evil, pecuniary profit was a consideration of small importance: his motives to literary labour seem uniformly to have arranged themselves as follows, utility, reputation, profit.

The work in question is certainly too brief, considering the importance of the subject: many parts of it, the theory of Huygens, Euler, and Franklin for instance, seem to have merited more discussion. That all the phenomena of light depend on the Sun, as the reservoir, whence all the emanations of that fluid to the various parts of the system are supplied, the lighting of a candle is alone sufficient to refute. The facts discovered to us by modern Chemistry will suggest a great many other doubts of the doctrines respecting light, which were regarded as well established when Dr. Priestley’s book was written. But it was a faithful account of the knowledge of the day, and an unprejudiced tribute to the reputation of those philosophers who had from time to time extended the boundaries of science on the subjects treated of.

Not a little has been added to the mass of facts then published, by the subsequent experiments of Dr. Priestley himself, and his fellow labourers in the Chemistry of the Gasses: and notwithstanding the experiments of Sir Isaac Newton and his predecessors, the theory of light and colours is not yet rested upon facts sufficiently numerous, and decisive to satisfy the enquiries dictated by the present state of knowledge.

But with all these disadvantages, the work has nevertheless maintained its ground, for we have no where else so systematic, and compleat, though brief an account of what had been made known to the world on this important branch of scientific inquiry. It will always remain a valuable performance; and to the author an honourable one, from the knowledge and ability required in its compilation, from the fairness of the account it gives, and the entertaining statement of facts and suggestions interspersed through the book.

It is greatly indeed to be wished, that these histories should be continued on the plan which Dr. Priestley has adopted. So that all the prominent facts should be collected in the order of their discovery, and a full view be given of the ground already gone over. Abridgments, do not answer this purpose; the theories that dictated the experiments are not detailed, their truth or their fallacy cannot be judged of, and sufficient merit is not attributed to the labours of the discoverer, or the bearings of his facts on his theory, sufficiently explained. To attain gradually to the summit of the temple of science, we must not only build on the foundations of our predecessors, but know somewhat of their intentions at the time of laying them.

The minor treatises of Dr. Priestley on electricity, perspective and natural philosophy, have this discrimination of character, that they are more calculated to allure young people to the study of those subjects than almost any of the introductions which have either preceded or succeeded. Philosophy is made, not an abstruse science, but a delightful amusement. Indeed it was the fort of Dr. Priestley to make knowledge intelligible and popular, and treat it in such a way, as to invite rather than deter, those who were inclined to enter upon these delightful pursuits. The plainness and simplicity of his syllabus, the amusing complexion of the Phenomena, by which he illustrates his doctrines, and the facility with which the one can be made, and the other comprehended, affords a very useful example to those who may have the same object hereafter in view. This was doubtless, owing to his long experience as a teacher: and his success in that capacity among his pupils, with the electrical machine, and the air pump, is full evidence of the practical utility of his plans of instruction.

_Catalogue of Dr. Priestley’s smaller pamphlets and uncollected papers on philosophical subjects._

_Nicholson’s_ } _Journal._ } _new series._ }

V. 1 p. 181. Reply to Mr. Cruikshank’s. Ibid 198. Experiments on the Pile of Volta. V. 2 p. 233. On the conversion of iron into steel. V. 3 p. 52. On air from finery cinder and charcoal. V. 4 p. 65. Farther reply to Mr. Cruikshank’s.

_Amer. Trans._

V. 4 p. 1. Experiments and observations relating
to the analysis of atmospherical
air.
V. 4 p. 11. Farther experiments relating to the
generation of air from water.
Ibid p. 382. Appendix to the above articles.

_Ib. Vol._ V. {p. 1. Experiments on the transmission
{ of acids and other liquors in the
{ form of vapours over several substances
{ in a hot earthen tube.
Republished {
{p. 14. Experiments on the change of
{ place in different kinds of air
{ through several interposing substances.
{ 21. Experiments relating to the absorption
{ of air by water.
{
{ 28. Miscellaneous experiments relating
{ to the doctrine of phlogiston.
together. {
{ 36. Experiments on the production of
{ air by the freezing of water.
{
{ 42. Experiments on air exposed to
{ heat in metallic tubes.

_New-York Med. Repos._ _Title and Date._

Vol. 1 p. 221. Considerations on the doctrine of
Phlog. and the Decomp. of water.
(Pamphlet) 1796.
Ibid p. 541. Part 2d of do. (Pamphlet 1797.)
Vol. 2 p. 48. (Pamphlet) to Dr. Mitchell.
Ibid p. 163. (Pamphlet) on Red Precipitate of
Mercury as favourable to the doctrine
of Phlogiston, July 20, 1798.
Ibid p. 263. Experiments relating to the calces of
metals communicated in a fifth letter
to Dr. Mitchell. October 11,
1798. (Pamphlet.)
Ibid p. 269. Of some experiments made with
ivory black and also with diamonds.
(Pamphlet) 11 October, 1798.

Ibid p. 383. On the phlogistic theory, January 17,
1799. (Pamphlet.)

Ibid p. 388. On the same subject. February 1,
1799.

Vol. 3 p. 116. A reply to his antiphlogistian opponents,
No. 1.

Vol. 4 p. 17. Experiments on the production of
air by the freezing of water.

Ibid p. 135. Experiments on heating Manganese
in inflammable air.

Ibid p. 247. Some observations relating to the
sense of hearing.

Vol. 5 p. 32. Remarks on the work entitled “A
brief history of epidemic and pestilential
diseases,” May 4, 1801.

Ibid p. 125. Some thoughts concerning dreams.

Ibid p. 264. Miscellaneous observations relating
to the doctrine of air, July 30,
1801.

Ibid p. 390. A reply to Mr. Cruikshank’s observations
in defence of the new system
of chemistry, 5 Vol. Nicholson’s
Journal p. 1, &c.

Vol. 6 p. 24. Remarks on Mr. Cruikshank’s experiments
upon finery cinder and
charcoal.

Ibid p. 158. Observations on the conversion of
iron into steel.

Ibid p. 271. Additional remarks on Mr. Cruikshank’s
experiments on finery cinder
and charcoal, November 15
1802.

APPENDIX, NO. 2.

_Of Dr. Priestley’s Metaphysical Writings._

The principal source of objection to Dr. Priestley in England, certainly arose from his being a dissenter; from his opposition to the hierarchy, and to the preposterous alliance, between Church and State: an alliance, by which the contracting parties seem tacitly agreed to support the pretensions of each other, the one to keep the people in religious, and the other in civil bondage. His socinian doctrines in theology, and the heterodoxy of his metaphysical opinions, though they added much to the popular outcry raised against him, were not less obnoxious to the generality of Dissenters, than to the Clergy of the Church of England. Nor is it a slight proof of the integrity of his character, and his boldness in the pursuit of truth, that he did not hesitate to step forward the avowed advocate of opinions, which his intimate and most valuable friends, and the many who looked up to him as the ornament of the dissenting interest, regarded with sentiments of horror, as equally destructive of civil society and true religion.

The extreme difference observable between the apparent properties of animal and inanimate matter, easily led to the opinion of something more as necessary to thought, and the phenomena of mind, than mere juxta position of the elements, whereof our bodies are composed. The very antient opinion also of a state of existence after death, prevalent in the most uncivilized as well as enlightened states of society, confirmed this opinion of a separate and immortal part of the human system: for it was sufficiently evident, that no satisfactory hopes of a futurity after death, could be founded on the perishable basis of the human body. It is only of late days, and from the extension of anatomical and physiological knowledge, that the theory, and the facts of animal organization have been at all understood; and without the conjunction of physiology with metaphysics, the latter would have remained to eternity, as it has continued for ages, a mere collection of sophisms, and a science of grammatical quibbling. The doctrine of a future state, and that of an immaterial and immortal soul, became therefore mutual supports to each other; and herein the civil power willingly joined in aid of the dogmas of metaphysical theology, from observing the convenience that might arise in the government of civil societies, from inculcating a more complete sanction of rewards and punishments for actions in this life, by means of the dispensations in a life to come. Other causes also gave an universal preponderance to the theory of the human soul. It became, for the reasons above mentioned, not only a favourite doctrine with churchmen and statesmen, but the self delusions among the vulgar, respecting supposed appearances after death, rendered it also a _popular_ doctrine. Indeed, in every age, and in every country, the priesthood have found it so powerful an engine of influence over the minds of the people, and in too many cases, so, fruitful a source of lucrative imposture, that its prevalence is not to be wondered at, wherever artificial theology has been engrafted on the simplicity of true religion, and supported by an established clergy. Of Popery, which yet remains the prevailing system of the christian world, it is doubtless the corner stone; and even under every form of ignorant and idolatrous worship throughout the globe, it is the main source of power and profit to that class of society, which regulates the religious opinions, rites and ceremonies of the country. Not that I would insinuate, that the belief of a separate soul, like some other opinions that might be mentioned, has been generally taught by professors who disbelieve it; for plausible arguments are not wanting, to give it that currency which it has so long received among the wisest and the best of men: nor that an established priesthood of any age or country, or of any religion, is a mere compound of fraud and imposture, for I well know that the wise and the good are abundant in this class of society, as well as in others. But even such men are liable to the common infirmities of human nature; they cannot be indifferent to their rank in society, or the means of their subsistence; it is not every college youth, that is able or willing to weigh “the difficulties and discouragements attending the study of the Scriptures,” so forcibly pointed out in the melancholy pamphlet of Bishop Hare: nor is it every professor of Christianity, who doubts of the doctrines he has undertaken to teach, that has fortitude enough to follow the noble example of Theophilus Lindsey, and John Disney. Hence we may take for granted, that those opinions will be admitted the most readily, and enforced the most willingly, which contribute to the influence of that order, which the professors have been induced by choice, or compelled by necessity, to wed for life. Choice indeed, at least that kind of choice, which depends on a well-grounded conviction of the object chosen being the means of superior usefulness, has little to do in this business. For though the clergy of the church of England severally declare that they are moved by the Holy Ghost to take upon them the clerical character, is there one among them in the present day (Bishop Horsely perhaps excepted) who would venture to defend this declaration in the sense originally intended? It is a fact notorious, that the candidates for holy orders, regard the profession of Divinity as they would that of Physic or Law, a fair and reputable means of gaining a livelihood, by performing those duties which are considered as necessary to the well being of society. It is a fact too, equally notorious, that wherever theological opinions (like that of the human soul) have been fit and liable to be made subservient to the temporal profit or influence of the clergy, that use has been so made of them by the ambitious and designing part of the profession, and the rights of the people have been encroached upon, to serve the interest of the Hierarchy. Nor is it the established clergy alone that some of the preceding remarks will apply to: much bigotry among the clergy of the dissenting interest, may fairly be ascribed to similar causes, though by no means operating in the same degree.

But important as this doctrine is to the clerical order in political societies, some latitude of doubt and even of denial, has been conceded in England to the known friends and adherents of the established system in that country. This is the more to be wondered at, as they have generally considered a dissonance of opinion among their own order, more fatal to the common interest, than the attacks of their avowed enemies. Thus, more notice was taken of the Arian heterodoxy of Dr. Clarke, than of the avowed infidelity of Collins, Tindal, Toland, Coward, and other writers of that class, who published about the same period.