71S 



nary or total, the whole theory, as he has left it, is analytically 

 complete : but the geometrical interpretations in the general case of 

 total reflexion at the surface of a crystal present very great difficul- 

 ties. -Many of these his acute intellect had with gi-eat labour sur- 

 mounted ; he had been working hard at the subject for the last four 

 weeks of his life, and with so much success, that he had actually 

 commenced a new paper for the Irish Transactions, embodying the 

 results of his latest investigations. The heading of this paper, which 

 I have already mentioned, remains in his own handwriting. It is 

 believed that several of his manuscripts on other subjects are in the 

 possession of his family, although it was not his custom to preserve 

 many vrritten papers, 



Alexaxder Broxgxiakt, the son of a distinguished architect, 

 was born at Paris in the year 1770, In early youth he derived his 

 love of science, not only from his father, but also from his father's 

 friends, Fr?mklin, Lavoisier, and other eminent nien of the day. 

 He received his earliest lessons in science at the Ecole des Mines, 

 and afterwards at the Ecole de IMedecine. At the age of tsvent}', 

 he came to England, and visited the mines of Derbyshire. On 

 his return to his own country-, he published a memoir on enamel- 

 Eng, which induced M. Berthollet, several years later, to recom- 

 mend his appointment to the office of Director of the manufactory 

 of Se\Tes. At the time of the French Revolution, he had the mis- 

 fortune to be suspected of the offence of favouring the escape of 

 i\E Broussonet, and was thrown into prison. ^More fortunate however 

 than so many others v.dio were arrested in that tendble time, he 

 escaped with his life, and, after his release, returned to Paris and be- 

 came a ]\Emng Engineer. , He subsequently was appointed Professor 

 of Natural History at the Ecole Centrale des Quatre Xations ; and in 

 the year 1800, commenced his superintendence of the manufactory 

 of porcelain at Sevres, an office filled by him for the long period of 

 nearly half a century. 



In the year 1S07, appeared M. Brongniart's Trait e Elementaire 

 de ]\nneralogie,' a work of gi'eat importance and merit. 



M. Brongniart did not confine liis scientific researches to mine- 

 ralog}". Zoology also attracted his attention and profited by his 

 labours, and a community of pursuit brought him into close relation 

 with the illustrious Cuvier. 



In the year 1S03, he revisited this country and studied its fresh- 

 water formations, a study of great importance Avitli reference to a 

 v.-ork published by liim, in conjunction with Cuvier, after his 

 return to France, on the Geology of the Environs of Paris. 



In consequence of the great service he had rendered to science, 

 he was elected a member of the French Academy in the year 1815. 

 Two years later, he visited Switzerland, the Alps and Italy, where he 

 extended his geolo2:ical fame by fresh observations ; and in 1822, he 

 published the second and enlarged edition of his Geology of the 

 neighbourhood of the capital of France. 



In the year 1824, he made a journey in Norway and Sweden, and 



