TROOST, Gerard, mineralogist, born in Bois Le Due, Holland, 15 March, 1776; died in Nashville, Tennessee, 14 August, 1850. He was educated at the universities of Leyden and Amsterdam, where he devoted special attention to chemistry, geology, and natural history. In 1801 he received the degree of master in pharmacy from the latter university. For a time he practised his art at the Hague and elsewhere, but soon went to Paris, where he became the pupil of the Abbe Hahy. In 1809 he was appointed by Louis Bonaparte, then king of Holland, scientific attache of a naval expedition to Java, but he was captured by an English privateer, and, after confinement in Dunkirk, returned to Paris. He then made his way on an American sailing vessel from La Rochelle to Philadelphia, hoping thence to reach Java. Soon after his arrival in the United States, Louis Bonaparte relinquished the throne, and Java was surrendered to the English. In consequence he determined to remain in Philadelphia, where, in 1812, he assisted in founding the Academy of natural sciences, and was its president in 1812-'17. The first works in the United States for the manufacture of alum were organized by him in 1814 at Cape Sable, Maryland ; but the enterprise was unsuccessful. He returned to Philadelphia, and in 1821 was appointed professor of mineralogy in the Philadelphia museum, he delivered public lectures on that branch and on chemistry at the Philadelphia college of pharmacy, also making geological excursions into New Jersey, New York, and elsewhere. In 1825 he removed to New Harmony, Indiana, with Robert Owen and others, but, becoming dissatisfied, settled in Nashville in 1827. He was appointed professor of chemistry, geology, and mineralogy in the University of Nashville in 1828, which chair he held until his death, and in 1831 he was made state geologist, an office he filled until 1849. Professor Troost gathered an extensive collection of minerals, including about 15,000 specimens, as well as more than 5,000 geological specimens and various other articles, constituting a cabinet that at that time was considered the finest in the possession of a single individual in the United States. He was a member of many scientific and philosophical societies in the United States and Europe, and translated into Dutch Alexander yon Humboldt's "Aspects of Nature." Besides numerous contributions to the transactions of learned societies, he published a "Geological Survey of the Environs of Philadelphia" (Philadelphia, 1826), and nine "Annual Geological Reports of Tennessee " (Nashville, 1835-'48).