Part 13

Many unbelievers have, no doubt, borne with great patience severe calamities; they have suffered death with great fortitude when engaged in a good cause, and many have courted death to serve their friends or their country. It must however be allowed that there is no great merit in meeting death with fortitude when it cannot be avoided, and likewise that the above cases cannot be absolutely calculated upon, as there is no sufficient motive to account for their conduct. But upon a truly practical christian there is the greatest dependance to be placed for acting well in all the situations in which he may be found, his highest interest being connected with the performance of the greatest duties; and even supposing that many persons, who are not christians, from favourable circumstances attendant upon their birth and education, and from a naturally happy temperament of body and mind, may, and, it must be allowed do acquire a habit of disinterested benevolence and may in general be depended upon to act uniformly well in life, still the christian has a decided advantage over them in the hour of death, as to consider death as necessary to his entering upon a new and enlarged sphere of activity and enjoyment, is a privilege that belongs to him alone.

APPENDIX, NO. 1.

_Of the discoveries in factitious Airs before the time of Dr. Priestley, and of those made by himself._

Dr. Priestley has given a general though brief account[33] of what had been done by his predecessors in this department of experimental Philosophy, and Sir John Pringle in his discourse before the Royal Society on occasion of presenting Dr. Priestley with the Copley Medal in 1772[34] has entered expressly, and more fully into the history of pneumatic discoveries. The same subject was taken up about three years after by Mr. Lavoisier still more at large, in the introduction to his first Vol. of Physical and Chemical Essays, of which a translation was published by Mr. Henry of Manchester in 1776. It is unnecessary to detail here what they have written on the history of these discoveries. It may be observed that no mention is made by any of these gentlemen of an experiment of Mr. John Maud, in July 1736[35], who procured (and confined) inflammable air from a solution of Iron in the vitriolic acid. Inflammable air had been procured from the White Haven coal mines, and exhibited to the Royal Society by Mr. James Lowther, but I do not recollect any notice of its having been collected from a solution of metals in acids, and its character ascertained before Mr. Maud’s experiment; for Hales, though he procured both inflammable and nitrous air, did not examine their properties. But it is much more extraordinary that neither Sir John Pringle who was a Physician, or Mr. Lavoisier who was so much occupied under government, respecting the Theory of the formation, and the practice of manufacturing Saltpetre from Nitre beds, should not have known, or have noticed the five treatises of Mayow on chemical, phisiological and pathological subjects, published a century preceding. Mayow is quoted by Hales,[36] by Lemery,[37] and by Brownrigg,[38] but though they appear to have read his work, it is evident that they knew not how to appreciate, or to profit by it. Haller[39] also refers to him, and he is respectfully quoted by Blumenbach[40]: but his book nevertheless long remained in comparative obscurity. From their time Mayow has been neglected until his writings were noticed by Dr. Forster, in 1780,[41] and again announced as almost a discovery in the chemical world, by Dr. Beddoes in the year 1790. His doctrines touch so nearly on the subsequent discoveries of Priestley, Scheele, Lavoisier, Crawford, Goodwin, &c. that it seems absolutely necessary to discuss his pretensions, before those of his successors can be accurately admitted. As I am acquainted with Dr. Beddoes’s pamphlet on Mayow, from the analytical review of it only, (V. vi.) and have no opportunity here of consulting it, I shall take up Mayow’s book, and give an account of his tenets, from the work itself.

[33] In the beginning of his first vol. of experiments: it is an abridgment of Sir J. Pringle’s discourse.

[34] Discourses p. 4.

[35] Martyn’s abridgment of the Philosophical transactions v. 9. p. 396. I think Maud’s experiment in 1736 likely to have suggested those of Mr. Cavendish in 1766.

[36] Vegetable Statics v. 2. p. 234.

[37] Mem. de l’Acad. Royale 1717 p. 48. On ne dit pourtant point trop sous quelle forme ce nitre se contient dans l’air, et Mayou, Auteur Anglois et grand defenseur du Nitre-Aèrien voulant èclaircir cette difficultè, suppose l’air impregnè par tout d’une espece de nitre metaphysique, qui ne merite pas trop d’ètre refutè, quoi-qu’il l’àit cependant ètè suffisamment par Barchusen et par Schelhamer. Le fondement de l’opinion du Nitre aèrien, c’est comme le rapporte Mayou lui mème, qu’apres avoir enlevè à une terre tout le Nitre qu’elle contenoit, si on l’expose ensuite à l’air pendant un certain tems elle en reprend de nouveau: il est vrai que si l’observation ètoit parfaitement telle qu’elle vient d’ètre rapportèe, on auroit une plus grande raison qu’on n’en a, de supposer dans l’air une très-grande quantite de nitre, et de mettre sur le compte de ce nitre aèrien un grand nombre d’effets auquels il n’a certainement aucune part.

The experiment of Lemery mentioned in Dr. Watson’s Essay on Nitre, is in p. 54 of the Mem. de l’acad. royale for 1717 not for 1731.

It sometimes happens to men whose genius far transcends the level of their day, to be from that very circumstance neither understood nor believed by their contemporaries. Until the discoveries of modern chemistry, who would have given Sir Isaac Newton credit for his conjecture that the Diamond was an inflammable substance? The fact which Lemery sneers at, the reproduction of nitre in the earth, is established beyond contradiction by the authors quoted by Dr. Watson (Chem. Ess. v. 1. p. 318-321) and in Bowle’s account of the nitre earths in Spain, and in Andreossi’s memoir on the Saltpetre of Egypt. Though it is far from improbable that after lixiviation these earths may again become gradually impregnated with putrefying animal or vegetable matter to serve for the future crops of nitre.

[38] Philosophical transactions v. 55 p. 232.

[39] Dr. Priestley in his preliminary account of the discoveries and theories on respiration (Exp. on air v. 3 p. 356. abridged edit.) quotes Haller’s great work on Physiology. Haller quotes Mayow in three or four places; but it is no wonder the quotations did not strike Dr. Priestley with any curiosity to examine Mayow’s book, for Haller certainly did not understand his theory. For instance Lib. 8. § 13. Nitrum aereum. Si ad verum sensum nitri aerei hypothesis revocata fuisset parum utique ab eà differt quam novissimè proposuimus. Nitrum quidem ipsum incautiosius olim Physiologi in aere obvolitare scripserunt, et ex pluvià et nive colligi; idemque passim ex rupibus efflorescere (Sprat ex Henshaw p. 264 major cal. hum.) exque plantis et stercoribus educi (Fludd Niewentydt, 563-4. Mayow de nitro aereo. Lower de Corde c. 3. Thurston 52. 53. Besse Analyse tom 1 et en lettre en reponse à M. Helvet. 114.) id nitrum aiunt in pulmonibus ad sanguinem venire, et ab eo ruborem illum elegantem, et fermentationem (Mayow, Thurston penult. ess. T. 3 p. 265) et calorem sanguinis accedere aut vicissim sanguinem condensari.

Certainly the id nitrum, is not Mayow’s. M. Rosel seems first to have ascertained the existence of nitre in plants. A late experiment of Dr. Priestley’s, of which he gave an account in a letter to Dr. Wistar, seems to make it probable that there may be nitre in snow.

[40] Blumenbach’s Physiology, Caldwell’s translation, Philadelphia, 1795. § 162. Speaking of the theories of animal heat, “But all these hypotheses are embarrassed with innumerable difficulties; whereas on the other hand the utmost simplicity, and an entire correspondence with the phenomena of nature combine in recommending and confirming that doctrine in which the lungs are considered as the focus or fire place where animal heat is generated, and the deplogisticated part of the air which we breathe as the fuel that supports the vital flame. That justly celebrated character Jo. Mayow sketched out formerly the leading traces and the first great outlines of this doctrine which in our times has been greatly improved, extended and farther elucidated by the labours of the illustrious Crawford.”

Dr. Darwin however is certainly right in supposing that heat is evolved in many other processes of the animal economy, beside inspiration.

[41] See the translation of Scheele by Dr. John Reinhold Forster 1780 p. XIII.

In p. 437 of v. 5 of the analytical review of Hopson’s Chemistry, before Dr. Beddoes’s account of Mayow in 1790 the latter is stated as the author of discoveries that might have given rise to the present system of pneumatic Chemistry.

Two of Mayow’s Essays, viz. de Respiratione and de Rachitide, appear to have been published at Leyden, in 1671, the author who died at the age of 34, being then 26 years old. The propositions which I have thought it necessary to extract from Mayow’s work, (ed. of 1674, Oxford,) and which I shall insert, will give a concise, but faithful view of his discoveries and conjectures in pneumatic Chemistry.[42] The abridgements of Beddoes and Fourcroy, I have no opportunity to consult, and as Mayow’s book is far from being common, I have deemed it by no means an unnecessary labour to give the reader an opportunity of judging for himself, what is the precise extent of the claim, which the patrons of Mayow’s reputation may fairly set up. It is also, of the more importance in a history of this subject, to notice the pretensions of this writer, as it appears that Boyle’s experiments on artificial air, in his physico-mechanical experiments were not made until the year 1767 et seq. Though the first edition of that treatise repeatedly quoted by Mayow was in 1661. Mayow’s experiments therefore ought to have been, and probably were known to Boyle at the publication of his last edition.[43]

[42] I believe Dr. Beddoes gives no more than the heads of each chapter and, a brief analysis of the contents. Dr. Beddoes in his remarks on Fourcroy’s account of Mayow, Ann. de Chimie. No. 85, Nich. Jour. v. 3 quarto p. 108 states Mayow at the time of his death to have been only 27 and 28: but he was born in 1645 and died in 1769. Biog. Dict. 8vo. ed. of 1798.

[43] I do not find that Boyle quotes Mayow, though their labours in the same field were contemporary. But Boyle in his hidden qualities of the air published in 1674 has an observation that looks as if derived from Mayow. “And this undestroyed springiness of the air, with the necessity of fresh air to the life of hot animals, suggests a great suspicion of some vital substance if I may so call it, diffused through the air, whether it be a volatile nitre or rather some anonymous substance, sidereal or subterraneal, though not improperly of kin to that which seems so necessary to the maintenance of other flames.”

The following is an analysis of Mayow’s essays, so far as relates to his chemical Philosophy.

CHAP. _1st. Of Nitre._ The air is impregnated with a vital, igneous, and highly fermentative spirit of a nitro-saline nature, p. 1.

Nitre is a salt consisting of an acid and an alkaline part, as appears by the Analysis, and by the generation of nitre; for if this salt be deflagrated with sulphur, the acid spirit will fly off, and may be collected by means of a tubulated retort and a receiver: and so if it be deflagrated with tartar, the residuum will be equal in weight to the tartar employed, though much of that, is of a fœtid oily nature. This appears also from the composition of nitre, by the addition of spirit of nitre to an alcali, p. 2-4. The fixed part of nitre is obtained from the earth; pure earth being probably a compound of salt and sulphur. p. 8.

CHAP. _2d. On the aereal and fiery spirit of nitre._

The air seems to contain an acid, as appears from the regeneration of vitriolic acid after the calcination of Vitriol, and from the rusting of steel filings in a moist air; p. 10. A component part of the acid of nitre, is derived from the air, which evidently contains something necessary to the support of flame. But this aereal pabulum of flame, is not air itself, for air remains when the confined taper is extinguished: nor is it as vulgarly supposed, the salt called nitre, p. 12. But that these fire-air particles exist also in nitre is evident, since this salt will support the combustion of sulphur in vacuo. Fill a tube with gunpowder slightly moistened, and it will burn out in vacuo, or with its mouth inverted over water. Hence the aereal part of nitre, is the same with the fire-air particles of the atmosphere, and is one component part of the acid spirit of nitre: the other being (like the fixed part) obtained from the earth, p. 17. 18. The fiery particles thus common to nitre and to the air, he denominates nitro-aereal. It is these that give causticity to spirit of nitre, and occasion the red fumes observed in distilling it, p. 18. They do not take fire of themselves in nitre, because they are inveloped with moisture; but when combined with salt of tartar, and thrown on the fire in a dry state they inflame, p. 20.

CHAP. _3d. Of the nature of the nitro-aereal and fiery spirit._ Fire he conceives to consist of these nitro-aereal particles set in violent motion by means of sulphureous bodies, in the cases of culinary fire: but by some other means, in the cases of the solar rays collected by a burning glass, and of the celestial fires. The corrosive and caustic nature both of fire and nitrous acid, seems to argue that it proceeds in both from the nitro-aereal particles they contain, 22-24. That fire is not of a sulphureous nature is evident, for nitre will not take fire in an ignited crucible; but oil thrown in, takes fire immediately. So if a piece of metal be held over a candle, the fire particles pass through the metal, but the sulphureous smoke adheres to the under side. p. 27.

That the heat occasioned by a burning glass, consists of these nitro-aereal particles is evident, for diaphoretic antimony may be made, either first by calcination with a lens, or secondly, by the repeated affusion of nitrous acid, or thirdly, by the deflagration of nitre on the antimony. Diaphoretic antimony made by calcination, increases on weight,[44] by means of the nitro-aereal particles fixed in it by the process. p. 28, 29.

[44] It was first observed by John Rey in 1630 that metals calcined, gain weight by the absorption of air. See an account of his book by M. Bayen Journ. de Rozier 1775 v. 1 p. 48. There are also some experiments by Boyle that shew the accession of weight on the calcination of metals, but he does not seem aware of the theory. Shaw’s Boyle, Fire and Flame weighed v. 2 p. 394, &c.

CHAP. _4th. On the origin of acid liquors, and the earthy part of Spirits of nitre._ From p. 34, it appears that he knew nothing of the absorption and combination of his nitro-aereal particles in the vitriolic acid, during the combustion of sulphur, but explains the whole mechanically by the saline portion of the sulphur being broken down into minute pointed particles, by the violent attrition of the nitro-aereal particles, and so becoming fluid and sharpened. He seems too, not to know that the colcothar of martial vitriol is no component part of sulphur, p. 37. The same mechanical explanation he applies to the formation of the ligneous acids, and to the impregnation of the caput mortuum or colcothar of vitriol, with fresh acid by exposure of air. In the succeeding paragraph, p. 39, he supposes that marchasite (martial pyrites) imbibes the nitro-aereal particles from the atmosphere, and thus acid is formed. In like manner he explains the formation of acids produced by fermentation, by the collision between the nitro-aereal, and the sulphureo-saline particles of the mass. p. 41. So also he supposes nitrous acid to be produced by the detention of his nitro-aereal particles by the terrene saline particles found in the earth, p. 43. Hence he concludes generally, p. 43, that acid salts are formed from a saline basis brought into fusion or fluidity by the nitro-aereal part of the air: and sums up his theory of nitre, by stating it to be a triple salt, composed of nitro-aereal particles, united to a terrene basis forming the acid, which then unites to the fixed basis, supplied also by the earth.

CHAP. _5th. On Fermentation._ He gives in this chapter his theory of fermentation, as arising from the conflict of his nitro-aereal principle which he thinks may be termed mercury, and the sulphureous principle: evidently meaning by the latter, the Phlogiston of Stahl: and he states broadly, p. 60. that pure sulphur can never admit of accension, but by means of the nitro-aereal particles obtained from the atmosphere. The rest of his reasoning in this chapter, does not seem deserving of further notice.

CHAP. _6th. On the nitro-aereal spirit as the cause of rigidity and elasticity._ These he explains by the fixation and state of his nitro-aereal particles in bodies endowed with these properties. In p. 69 he endeavours to account why boiled water freezes sooner than that which has not been boiled; a fact which Dr. Black has made the subject of a paper in the 45th vol. of the Philosophical transactions. But his reasonings throughout this chapter are not calculated to add to his reputation, or to the mass of knowledge of the present day.

CHAP. _7th. The elastic force of the Air depends on its nitro-aereal particles. In what way exhausted air is reimpregnated with them. Of the elements of Heat and Cold._ This chapter contains experiments to shew that the elasticity of the air is owing to the nitro-aereal particles contained in it: which may be destroyed by the burning of a candle or other combustible substances, and also by the breathing of animals. When the atmospheric air contained in a glass jar inverted over water, will no longer support flame or animal life, the water rises in the jar, owing to the diminished elasticity of the air, not being able to counteract the pressure of the surrounding atmosphere on the water p. 100. He finds p. 101 that the diminution by burning a taper in a given quantity of the air, is about one thirtieth of the whole, and by the breathing of mice and other animals about one fourteenth. Thence he concludes p. 106 that by means of respiration the elastic part of the air enters into the blood, and that the sole use of the lungs is not as some suppose, to break down the blood in its passage into very minute particles. That combustion and respiration have similar effects on atmospherical air, he concludes, p. 108, from the fact, that a candle and a small animal inclosed together in a glass jar over water, the one will not burn, nor the other remain alive above half the time that they would if alone. Mayow however, did not consider his nitro-igneous and elastic particles to be either pure air, or even a component part of the common air, as air, notwithstanding the ambiguity of the passages in p. 114 and 118; but as particles of a different nature, attached to and fixed in the atmospheric particles; and detached (_excussas_) by the means above mentioned, p. 118 and 121. His explanation of elasticity generally in this chap. and of the difficulty arising from the obvious resistance to the Atmosphere, and the expansibility of the air in which a taper has been extinguished, or an animal died, seem too obscure and unintelligible to merit transcribing. It is evident however upon the whole from p. 123 compared with p. 100 and 135 that he conceived the diminution of such air to arise from diminished elasticity, but he supposes it to be denser than common air 123. In a subsequent part of this chapter p. 128 et seq. he states his theory of the manner in which deteriorated air recovers its loss, viz. that the nitro-aereal particles being lighter than the atmospherical, float abundantly in the higher regions; and that the part of the atmosphere deprived of them below, being forced upward by the pressure of the atmosphere above, obtains a renewal of these particles by mixture with the strata where they abound.

The element of fire, he supposes to reside in the body of the Sun, which is no other than a mass of nitro-aereal particles driven in perpetual gyration with immense velocity. Cold, which he considers as some thing positive (p. 130) he thinks consists in these particles assuming a pointed form, and moving not in gyration but strait forward. Much of his reasoning indeed throughout the book, savours greatly of the mechanical and corpuscular philosophy prevalent in his day.

CHAP. _8th. On the nitro-aereal spirit as inspired by animals._ Formerly he thought that in respiration the nitro-aereal particles were rubbed or shaken off (_atterere_, _excutere_ 146) from the common air by the action of the lungs, at present he thinks the air itself enters the mass of the blood, is there deprived of these particles, and of part of its elasticity. To prove this he produces an experiment of the diminution of air by the vapours from iron dissolved in nitrous acid: but the beautiful deductions of Dr. Priestley from a similar experiment, never occurred to him; on the contrary he expressly states that it is an Aura, but not Air p. 145 and though afterward in chap. 9 p. 163, 164 he inclines to doubt, yet again in p. 168 he denies it that character.

In p. 146 he proceeds to state the uses of these nitro-aereal particles, which (147) he considers as the principle of life and motion both in animals and vegetables. By the mutual action of the nitro-aereal, with the sulphureo-saline particles contained in the blood, a fermentation is excited necessary to animal life, and to the warm fluid circulation of the blood (_ad sanguinis æstum_.) To these particles imbibed from the air, he attributes the difference in colour between the venous and arterial blood; and he shews this, from the numerous air bubbles arising in an exhausted receiver from warm arterial blood: but his experiment to illustrate the difference, from the colour produced by the nitrous acid with vol. alk. seems very little to the purpose p. 150.

To the fermentation arising from this mixture of nitro-aereal particles with the blood, he ascribes animal heat, and accounts satisfactorily for the increased heat of the body during strong exercise, from the more frequent inspirations occasioned by the exertion (p. 152, 306:) but his replies to the objections of Dr. Willis, drawn from the phenomena of fermenting mixtures, are very inconclusive.