the structure of luminous flame, recently defended by Smithells (Chem. Soc. Trans. 1892, p. 217). According to Porrett, the light is mainly due to free carbon formed in the flame owing to the decomposition by heat of gaseous hydrocarbons. His ingenious experiments deserve repetition, and the observation that the luminous portion of the flame is surrounded completely by an almost invisible mantle, and that a spirit-lamp flame, though more transparent than glass, casts a shadow when placed in front of a candle flame, are of much importance. His chemical investigations on gun-cotton, published in 1846, are not of great value.
Porrett's sole contribution to physics was the discovery of electric endosmosis in 1816 (Thomson, Annals of Philosophy, viii. 74). The phenomenon had, according to Wiedemann (Galvanismus und Elektricität, 1st ed. i. 376), been observed previously by Reuss, but Porrett's discovery was independent, and the phenomenon for long went in Germany by his name.
Porrett's style is clear and unpretentious, his exposition methodical and workmanlike. Probably owing to lack of time, he did not attain the technical skill necessary to complete the investigations he began so brilliantly. It is unfortunate for science that a man of such marked capacity should have given to it only his leisure. The following is a list of his scientific papers: 1. In the ‘Transactions’ of the Society of Arts: ‘A Memoir on the Prussic Acid’ (1809, xxvii. 89–103). In Nicholson's ‘Journal:’ 2. ‘On the Prussic and Prussous Acids’ (1810, xxv. 344). 3. ‘On the Combination of Chlorine with Oil of Turpentine’ (1812, xxxiii. 194). 4. ‘On the Explosive Compound of Chlorine and Azote’ (in conjunction with R. Kirk and W. Wilson) (1813, xxxiv. 276). In the ‘Philosophical Transactions:’ 5. ‘On the Nature of the Salts termed Triple Prussiates, and on Acids formed by the Union of certain Bodies with the Elements of Prussic Acid’ (6 June 1814, p. 527). 6. ‘Further Analytical Data on the Constitution of Ferruretted Chyazic and Sulphuretted Chyazic Acids,’ &c. (22 Feb. 1815). In Thomson's ‘Annals of Philosophy:’ 7. ‘Curious Galvanic Experiments’ (1816, viii. 74). 8. ‘Observations on the Flame of a Candle’ (viii. 337). 9. ‘On the Triple Prussiate of Potash’ (1818, xii. 214). 10. ‘On the Anthrazothion of Von Grotthuss, and on Sulphuretted Chyazic Acid’ (1819, xiii. 356). 11. ‘On Ferrochyazate of Potash and the Atomic Weight of Iron’ (1819, xiv. 295). In the Chemical Society's ‘Memoirs:’ 12. ‘On the Chemical Composition of Gun-Cotton’ (in conjunction with E. Teschemacher) (1846, iii. 258). 13. ‘On the Existence of a new Alkali in Gun-Cotton’ (iii. 287).
[Besides the sources mentioned above, obituaries in Chem. Soc. Journ. 1869, p. vii.; Proc. Roy. Soc. vol. xviii. p. iv.; Proc. Soc. of Antiquaries, 2nd ser. iv. 305; Poggendorff's Biographisch-literarisches Handwörterbuch zur Gesch. der exakten Wissenschaften; Porrett's own papers.]
PORSON, RICHARD (1759–1808), Greek scholar, was born on 25 Dec. 1759 at East Ruston, near North Walsham, Norfolk, where his father, Huggin Porson, was parish clerk; his mother, Anne, was the daughter of a shoemaker named Palmer in the neighbouring village of Bacton. Richard was the second of four children, having two brothers and a sister Elizabeth (1756–1842). He was sent first to the village school of Bacton, and thence, after a short stay, to the village school of Happisburgh, where the master, Summers—to whom Porson was always grateful—grounded him in Latin and mathematics. The boy showed an extraordinary memory, and was especially remarkable for his rapid proficiency in arithmetic. His father meant to put him to the loom, and meanwhile took a keen interest in his education, making him say over every evening the lessons learned during the day. When Porson had been three years with Summers, and was eleven years old, his rare promise attracted the notice of the Rev. T. Hewitt (curate of the parish which included East Ruston and Bacton), who undertook to educate him along with his own sons, keeping him at his house at Bacton during the week, and sending him home for Sundays. For nearly two years Porson was taught by Hewitt, continuing his Latin and mathematical studies, and beginning Greek. In 1773, when the boy was thirteen, Mr. Norris of Witton Park, moved by Hewitt, sent him to be examined at Cambridge, with a view to deciding whether he ought to be prepared for the university. The examiners were James Lambert [q. v.], the regius professor of Greek; Thomas Postlethwaite [q. v.] and William Collier, tutors of Trinity College; and George Atwood [q. v.], the mathematician. Their report determined Mr. Norris to send Porson to some great public school. It was desired to place him on the foundation of the Charterhouse, but the governors, to whom application was made, had promised their nominations for the next vacancies; and, eventually, in August 1774, he was entered on the foundation of Eton College. At
