322 Biographical Account of [Noy. 



His profound knowledge had, with great propriety, attracted the 

 attention of the Royal Academy of Sciences, of which he was 

 elected a Member in 17&4. He took his seat by delivering a dis- 

 course on the Methods employed in Chemistry, and their certainty. 

 When, in 1787? he became President of the Academy, he delivered 

 a discourse on Different Things which may be applied to Useful 

 Purposes. He had several years before translated the panegyric of 

 the Academy on the celebrated Torbern Bergman. 



The 24 dissertations enumerated below, and published by the 

 Academy in the course of 30 years, afford abundant proof of Mr. 

 Hjelm's zeal for the sciences. His discovery of molybdenum has 

 given him a distinguished place in the history of science ; nor will 

 his industry and assiduity as an officer and a citizen be soon for- 

 gotten. 



The following is a list of the works of this industrious philo- 

 sopher : — 



I. Published in the Memoirs of the Swedish Academy of 



Sciences. 



1. On the population of the diocese of Upsala, between 1749 

 and 1773. Published in the volume for 1776- 



2. Experiments on the diminution of bulk of different species of 

 trees when converted into charcoal. 1780. 



3. On the constituent parts of pitcoal and charcoal. 1781. 



4. Inquiry whether lime enters into the composition of sugar. 

 1783. 



5. Experiments showing that manganese exists in brunsten (black 

 oxide of manganese). 1785. 



C. Dissertation on the nature and constituents of steel. 1787- 



7. A flux useful in essaying lead ore, &c. 1~87- 



8. On a salt in marsiiberry juice (karsba'rssaft). 17S8. 



9. Experiments on molybdena, and on the reduction of its oxide. 

 1788. 



10. First continuation of the preceding paper. 1789. 



11. Second continuation of ditto. 1789. 



12. On the quantity of oxygen gas in black oxide of manganese. 

 1789. 



13. Third continuation of the paper on molybdenum. 1730. 



14. Fourth continuation of ditto. 1790. 



15. Fifth continuation of ditto. 1791. 



16. Sixth continuation of ditto. 1791. 



17. Seventh continuation of ditto, and conclusion. 1792. 



18. Of the useful purposes to which molybdenum may be 

 applied. 1793. 



19. Method of purifying lead from a mixture of gold and silven 

 1794. 



20. Experiments on the spring water at Almby farm, in the 

 parish of Gillberga, in Sddcrmanland. 1796. 



