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.