John, an eminent physician and natural philosopher, was born at Breda in 1730. He was first established in medical practice there, but removed to London in 1767, particularly with a view to study the improved methods of inoculation then recently introduced. Having become acquainted with Sir John Pringle, at that time President of the Royal Society, he was by him recommended to the Austrian ambassador, for the purpose of inoculating the Imperial family at Vienna, the Empress Maria Theresa having lost two of her children by the natural small-pox. He accepted this engagement in 1768, and having been perfectly successful in his operations, he was remunerated by the grant of a pension of £600 a-year for life, together with the titles of Aulic Counsellor and Physician to the Imperial Family. He was also consulted, in his medical capacity, by many others of the most distinguished personages at Vienna, and he enjoyed the particular esteem of the Emperor Joseph II., who was fond of receiving him in his cabinet, and of witnessing the exhibition of a variety of physical experiments, with which it was always the delight of Ingenhouzs to amuse and instruct his acquaintance of both sexes. The following spring he went to Italy, and inoculated the Grand Duke of Tuscany. He was made a Fellow of the Royal Society in May 1769; but he appears to have remained some years in Italy, for he was at Leghorn in January 1773; in March he dates from Salzburg; and in November 1775 from Vienna. The next year he was in London; and, in the winter of 1779, he went to Paris. The latter part of his life he spent principally in England, which, notwithstanding his dislike to the chillness of the climate, was always his favourite residence, and "where he enjoyed during many years," to use his own words, "that felicity which a free and independent man finds in the pursuit of knowledge and wisdom, in the society and friendly intercourse of those who have distinguished themselves by their learning."

Dr Ingenhouzs was cheerful in his disposition, and often playful in his conversation. Though his pursuits were chiefly scientific, he was not destitute of taste for literature and poetry. He had a particular predilection for Lucan, and for the Cardinal de Polignac, and would frequently recite passages from their poems with great energy, and with a strong German accent. Nor did he disdain the comforts of commercial opulence, and he was often a visitor at the magnificent villa of the late Mr Rucker of Roehampton. He had been introduced there by his friend Dr Brocklesby, who was in many respects of a perfectly congenial disposition, and who had great pleasure in prevailing on him to partake occasionally of his own hospitality, when his table would otherwise have been solitary. He died the 7th September 1799, at Bow Wood, in Wiltshire, the house of the Marquis of Lansdown, who had long known and esteemed him.

Dr Ingenhouzs's principal publications are,

1. **Experiments on the Torpedo.** Phil. Trans. 1775, p. 1. Mr Walsh had lately gained considerable reputation by his account of the effects of the torpedo. These experiments, which were made off Leghorn, in company with Dr Drummond, are merely illustrative of the properties of that animal, which are now better known; and they afford no decided test of the electrical nature of the phenomena.

2. **Methods of Measuring the Bulk of Mixtures of Common Air, and Nitrous Air, with Experiments on Platinum.** Phil. Trans. 1776, p. 257. The euclimetric apparatus is described as an improvement on Fontana's. The experiments are intended to show that platinum is not an alloy of iron and gold, since it may be deprived of all magnetic properties by repeated cupellation.

3. **A Way of Lighting a Candle by an Electrical Spark.** Phil. Trans. 1778, p. 1022. A very small charged jar setting fire to pulverised resin, strewed on cotton.

4. **On the Electrophorus,** p. 1027. This is a Bakerian lecture, read by appointment of the President and Council of the Royal Society, relating to the instrument then lately invented by Professor Volta, and which had been made known to the author by the Archduke Ferdinand. Its action is explained upon the elementary principles of the Franklinian theory. The next article in the volume contains some experiments of Mr Henly in confirmation of the doctrines here advanced.

5. **On a New Inflammable Gas.** Phil. Trans. 1779, p. 576. A powerful explosion is produced by the detonation of the vapour of a single drop of ether with oxygen gas. The author takes occasion to investigate the elasticity of the gas evolved by the detonation of gunpowder; and agrees with Bernoulli in estimating it as equivalent to near 2500 atmospheres. It may here be remarked, that notwithstanding Bernoulli's general accuracy, and great mathematical talents, he has fallen into a very singular error, in comparing the force of gunpowder with the daily labour of men; and has accidentally made the force of one pound equivalent to the daily work of 100 men, while, in fact, the force of 40 pounds is only equivalent to the daily labour of a single man.

6. **On a Mode of Suspending Magnetic Needles,** p. 537. Proposing that a hollow needle should be immersed in linseed oil, so as to press with a small portion of its weight only on its axis, in order that the friction may be greatly diminished.

7. **Improvements in Electricity,** p. 601. On plate m- INGENIOUS chimes of glass and pasteboard, and on a riband machine.

A Bakerian lecture.

8. Experiments on Vegetables. London, 1779. This volume is chiefly occupied by the detailed proofs of the author's principal discovery, that vegetables in general pour out a portion of oxygen gas in the sunshine, while they rather diminish its proportion at night and in the shade. It is dedicated to Sir John Pringle, and was translated into French by the author. Paris, 1786. Second edition, 2 vols. 8vo, 1787-9. Latin by Scherer. Vienna, 1785. Dutch by Dr Van Breda, of Delft, with others of his works.

9. On the Solubility of the Air at Sea, and at Places far removed from the Sea. Phil. Trans. 1780, p. 554. From the imperfection of the test employed, it was easy to imagine that some differences were discovered, which subsequent observations have shewn to have no existence.

10. Nouvelles Expériences et Observations, 2 vols. 8vo. Paris. On different subjects of natural philosophy. In German by Molitor, Vermischte Schriften. Vienna, 1784.

11. On the Influence of the Vegetable Kingdom in the Animal Creation. Phil. Trans. 1782, p. 426. Asserting the accuracy of his experiments, and denying some statements of Dr Priestley; advancing, in particular, many arguments to prove that the air obtained is really supplied by the vegetables, and not by the water in which they are usually immersed, in order to collect it. Dr Ingenhousz was, on all occasions, anxious to support his claims to this very interesting discovery; and he insisted that Priestley's earlier experiments, on the green matter contained in stagnant water, had little or nothing in common with his own, because that matter was, in fact, of an animal nature. He was in the habit of collecting the gas from cabbage leaves, and of keeping it bottled up in his pocket; and he was prepared with some coils of iron wire fastened into the corks, in order to exhibit the brilliant phenomenon of their combustion to his friends; the public being at that time less accustomed to this dazzling exhibition, than it has become in later years, when elementary lectures on chemistry have been more commonly addressed to mixed audiences than heretofore.

12. Essay on the Food of Plants, 8vo. London, 1798. From the French.

13. Dr Ingenhousz also inserted some essays in different volumes of the Journal de Physique; but they possess less originality and importance than his English publications. (Chalmers's Biographical Dictionary, xix. London, 1815, 8vo; Kesteloot in Biographie Universelle, xxi. Paris, 1818, 8vo.)