Electricity being then a subject of much philosophic discussion, he employed himself assiduously in experiments on that subject, and contrived many ingenious methods of improving electrical machines, varying the methods of employing them. He at that time contrived a small machine, which he always carried in his pocket, and with which he used occasionally to amuse his friends. This naturally produced a degree of intimacy and favour with Dr. Franklin, then in high favour with this country as a philosopher; and with him and Sir John Pringle he made one summer a short trip to Paris; and afterwards, with Dr. Franklin alone, a tour through Scotland and Ireland. He continued to pursue his philosophical and medical studies and acquirements in London till the year 1767, when he was recommended by Sir John Pringle to the Imperial Ambassador, to go to Vienna, in compliance with the Empress Maria Theresa's desire, to inoculate her family, to whom the small-pox had been fatal. Though Dr. Ingenhousz had never before practised, or thought particularly of inoculation, yet such was Sir John's opinion of his sagacity, docility, and general knowledge of physic, and steadiness of character, that, after practising inoculation for some months with Baron Dimsdale, at Hertford, he made no scruple to send him out as fully qualified for that important office, which he successfully executed in the year 1768; and in the year 1769 he inoculated the Grand Duke of Tuscany's family, at Florence. He declined many solicitations to inoculate at the Court of Turin; and, returning straight to Vienna, he was appointed Body Physician and Counsellor of State to their Imperial Majesties, with a pension for life. He continued in Vienna for some time, pursuing his philosophical and medical studies. What practice he attended to, I believe, was gratuitous.

He applied himself much to ingenious inventions and experiments; with which he used to amuse the nobility, foreign ministers, and curious strangers, at Vienna, in so striking a way as to gain himself a very high reputation for his natural magic.

He some time after obtained leave to travel to France, to gratify his original turn of mind, by witnessing the various experiments and discoveries in pneumatic philosophy which then began to attract the attention of Europe. He was resident in Paris during the first commotions which took place on the revolution; and was so completely terrified by the outrages then committed, that he conceived the most indelible detestation of the principles and practice of the democrats, which he ever retained. While at Paris he lived much with Rochfoucault de Maret, and with those other philosophers who were most eminent for their attention to, and discoveries in, pneumatic philosophy.

After his success at Vienna, he came to England, in January, 1778, and employed himself chiefly in the pursuit of pneumatic philosophy; for which purpose he retired to the country, near London, for some months; and, after a long and laborious course of close investigation, he published at London, in 1779, his expe

riments on vegetables, demonstrating their power of emitting vital air in sunshine, and azote in the night. These experiments he often repeated, improved, multiplied, and republished, on the continent, with various other philosophical essays, in French, German, and Latin editions. Of the Experiences sur les Vegetaux, he published at Paris, in 1787, the first volume, as a much augmented and corrected translation of the English publication of 1779; and, on his second journey to Paris, in 1789, a second volume of the same work, with much more extended views.

On his return to Vienna, he married a sister of Professor Jacquin, by whom he had no children, and with whom he did not live many years: his fondness for travelling, and his extreme attachment to England, engrossed the whole of his remaining life; and that will be best understood by attending to the chronology and analysis of his publications, which, being numerous, can be noticed in a life of this kind only in a summary way.

The order of his publications, separate from those already mentioned in our Transactions, are, first, his Experiments on Vegetables, published in London in 1779, before his first return to Vienna; a translation of which into Dutch was soon after published at the Hague, by Van Breda; and a German translation at Leipsic, by Molitor, in 1780; each of which was more enlarged than the original and, what is remarkable, there were four different editions, published in four different languages, of this work, and all of them in the course of a few months. The first French translation being published soon after he passed through Paris to Vienna, in the year 1780, a second and much enlarged German edition of this work was published at Vienna, in three volumes, in 1786: and a second French edition of the first volume of the same work was published at Paris in 1787; and the second, with many additional improvements, in 1789.

His Nouvelles Experiences sur divers Objets de Physique was published in German by M. Molitor, Professor at Mayeince; and a second part of the same in 1782: and a second edition of this work was printed in 1784, containing a number of papers already published in our Transactions: and all this happened before the publi cation of the original French edition, which, although it had been finished and sent to Paris in 1781, was very unreasonably delayed by the French publisher till 1785. This volume begins with a very correct and precise account of the system of electricity by Dr. Franklin and the second memoir is a very ingenious explanation of all the phenomena of the electrophorus invented by Volta on his theory of positive and negative electricity, the greatest part of which he had already published as a Bakerian Lecture in the Philosophical Transactions for the year 1778. In the third memoir he discusses at great length the much disputed question whether points or balls are the best contrivance to preserve buildings from the effects of lightning. He enters into an examination of Mr. Wilson's experiments performed at the Pantheon, and endeavours to establish the supe

riority of pointed conductors in opposition to that gentleman, who asserted that they ought to terminate in balls; which last, he says, will rather attract a strong shock; whereas the other, by acting at a much greater distance, will silently and gradually attract and convey to the earth the electrical fire, and so prevent its ever occasioning a severe stroke.

The following memoirs are chiefly employed in experiments on inflammable and dephlogisticated air; in describing air pistols, and lamps; a method of procuring inflammable air from marshes, and in other ways; how to produce the most dazzling light; and how to light a candle at pleasure with an electrical spark; several of which are to be found in our Philosophical Transactions.

In the 13th memoir we have a long account of the nature and best means of obtaining dephlogisticated air from various substances, and especially from nitre. He next republished his paper upon the salubrity of common air at sea compared with the air of the sea coast and of inland countries, which we have in the Transactions for 1780. We next have a memoir on magnetism and artificial magnets: next a republication of his theory of gunpowder, and of pulvis fulminans. The 18th memoir is on the passage of heat through, and inflammability of, metals; with an attempt to determine the quantity of phlogiston which different metallic and other bodies contain.

Previous to his publication on vegetables, in 1779, he had in the year 1775 published in our Philosophical Transactions, vol. lxv. his experiments on the torpedo, which at that time, from the previous experiments of Mr. Walsh, was exciting much attention; and that subject was further cultivated by experiments on the gymnotus, and by the very accurate anatomical observations of the late eminent Mr. John Hunter. In the year 1776 he published, in vol. lxvi., an easy method of measuring the diminution of bulk taking place in the mixture of common and nitrous air, according to the discovery of Dr. Priestley; and he there describes an instrument he had contrived, whereby this nice experiment might be performed with much more facility and accuracy. In the same paper he published his experiments on platina, which, then a new metal, he had taken much pains to investigate and render fusible. He valued highly a set of buttons of this metal, with which he had a coat mounted. found platina to be as completely, though not so strongly, magnetic as iron; and that this power was increased by fusion in electrical fire, which he first effected, whilst common fire was found to diminish it; and this magnetic virtue he constitutes as a specific property of platina, by which it may be always distinguished from gold, which cannot be rendered magnetic.

He

In the year 1778 we find a paper in the Phil. Trans. vol. lxviii. describing a ready way to light a candle by a very moderate electrical spark excited positively by a piece of glass, and a match made of cotton powdered with resin. In the 48th paper of the same volume we find electrical experiments to explain how far the phe

nomena of the electrophorus may be accounted for on Dr. Franklin's theory of positive and negative electricity, which he proves to agree perfectly with those exhibited by the late Mr. Canton with elder pith balls hanging by linen threads from a wooden box; which balls are excited either negatively or positively by a piece of excited glass.

In vol. Ixix., for the year 1779, he gives an account of a new kind of inflammable air, or gas, which can be made in a moment without apparatus, and is as fit for explosion as other inflammable gases in use for that purpose; together with a new theory of gunpowder.

In October of the same year (1779) he published the first edition of Experiments on Vegetables, before mentioned. To this he prefixes a most grateful dedication to Sir John Pringle, explaining at length the whole series of obligations he was under to him for his early patronage on his first arrival in this country, and for his very extraordinary mark of confidence and respect in recommending him to the Imperial Family of Germany, leaving this as a public testimony of his gratitude, being then about to return to Vienna.

In the end of vol. lxix., for 1779, we find a memoir on improvements in electricity, delivered as a Bakerian lecture, which were performed by the use of flat glasses, instead of globes or cylinders, which it now appears he had made use of for 15 years. In vol. lxx. for the year 1780, we find a paper on the degree of salubrity of the common air at sea in the Channel compared with that on the shore, and in various parts of Holland. In a letter written from Paris in January, 1780, and in vol. lxxii., for the year 1782, we find some further considerations on the influence of the vegetable kingdom on the animal creation.

In the year 1784 there were two volumes, in octavo, of his various philosophical papers published in German at Vienna. In 1785 we find Nouvelles Experiences et Observations sur divers Objets de Physique, which wholly consist of subjects of electricity, and the different kinds of air, being chiefly what had been before published in our Transactions. This he dedicates to Dr. Franklin, then residing at Paris, as Minister Plenipotentiary from the United States of America. In the year 1789 he published a second volume with the same title, dedicated to Baron Dimsdale, and printed under his own eye at Paris. The second volume contains chiefly experiments and observations relating to vegetables, and especially to that green matter produced in water, on which so much had been said by Dr. Priestley. These two volumes are pretty much the same with those that have been published in German, in which there were also some medical as well as physical papers, which, by a mistake of the editors, were omitted in the French edition.

His last publication, in the year 1798, preceding his death, is an essay on the food of plants and the renovation of soils, written at the desire of Sir John Sinclair, and published by the Board of Agriculture, of which he was President, and of which our philoso

pher had been made a Foreign Honorary Member. In this paper we have an abridged recapitulation and very ingenious application of his experiments and opinions, so fully illustrated in his Experiences sur les Vegetaux, published at Paris in two volumes, 8vo. in the year 1787 and 1789, to which he continually refers. He surely was the first who demonstrated clearly the singular facts of pure oxygen being continually emitted by vegetables when under the influence of light, by which the air was continually ameliorated, and that of their constantly emitting azote in the dark, by which it is corrupted. It is very true that Dr. Priestley had before him discovered that living plants always ameliorated the atmospheric air, by absorbing phlogiston, a theory in direct opposition to that of our philosopher, who thought this purification was occasioned by their perspiration instead of absorption, which continual absorption of atmospheric air he also allows; and proves, by some most ingenious experiments, that plants derive great part of their nourishment by their leaves; and that respirable air and heat are absolutely necessary to vegetation, though light is not, as they can grow very luxuriantly in the dark, but will emit no oxygen, acquire no green colour, and rather taint than ameliorate the air. As far as concerns the economy of vegetables, he certainly has thrown more light than any other philosopher since the time of Hales, whose ingenuity and success must render him immortal. Though it require too much of the reader's time to enumerate the variety of ingenious inventions and discoveries which he has published, yet I cannot omit making mention of that very brilliant experiment-the defla gration of solid iron in vital air; of which he was so very fond that he always carried a phial of it in his pocket, in which he used frequently to burn a piece of iron wire, to the great entertainment of his female friends.

ARTICLE II.

Chemical Analysis of Tin from the different Smelting Houses in Cornwall. By Thomas Thomson, M.D. F.R.S.

It would appear that there exists on the Continent a prejudice against Cornish tin, or an opinion that it is not pure, but artificially alloyed with some other metal. Some of the gentlemen connected with the tin trade in Cornwall conceived it possible that there might be some particular smelting-house which sent impure tin into the world, adulterating it artificially, for the sake of profit. To verify this suspicion, specimens of tin from every smelting-house in Cornwall were put into my hands, for the purpose of determining, by a careful analysis, the foreign metals with which they might be contaminated. I shall state in this paper the results which I obtained.