MENTELLE, Francois Simon, French explorer, born in Paris in 1731 : died in French Guiana, 21 December, 1799. His knowledge of geography and astronomy gained him professional employment, at an early age under the French government, and when it was determined to make an attempt to colonize a portion of Guiana he was ordered to accompany the first expedition, which landed at Cayenne in July, 1763. He laid out the city of Kouron, but colonists arrived more quickly than houses could be built for them, and most of them died of typhus fever. Mentelle escaped to Cayenne, where he was employed in laying out streets and in topographical work. He made several efforts to obtain permission to travel in central Guiana, the geography of which was then little known; but he did not succeed until 1766, when he accompanied a detachment that was sent to aid the natives on the right bank of the Maroni against the Maroon negroes of Surinam. The expedition returned to Cayenne on 13 June, after travelling more than 150 miles through the interior. Mentelle took every precaution to guard against the loss of the result of his labor, making every evening two copies of the notes that he had taken during the day, and placing them in different canoes. He drew a map of this journey, which is in the archives of Cayenne. In spite of His services, he was dismissed in 1777, and then conceived the idea of collecting the geographical materials relating to the country that were scattered through the archives of the government, or were in the hands of surveyors and engineers, and placing them in a museum of which he was to have the care. Pierre V. Malouet, who had been sent out to regulate the affairs of Guiana, obtained this post for him, with a salary of 2,000 livres. The French government refused him the necessary funds for further explorations, but he continued his labors, and in 1788 his services were rewarded with the cross of St. Louis. Besides his geographical work, he made, during his stay in Guiana, observations on meteorology and on the tides. He edited the " Ahnanach de Cayenne " for more than thirty years, during which his observations on the tides were of the greatest service to the planters of Surinam and Demerara, who were guided by then in draining the low lands and navigating the rivers. He was engaged at the time of his death in writing a memoir on the possibility of founding French colonies in Guiana. His valuable collection of maps and manuscripts was partly destroyed by the Portuguese when they seized Cayenne in 1809, but he had sent copies of them to Paris before his death, which were placed in the archives of the ministry of the navy.