Her first work was in French Guiana, under instructions from the colonial minister of France. This was in 1894. The following year she began the scientific exploration of the province of Para in northern Brazil, in collaboration with her husband, Henri Coudreau, who had previously distinguished himself by his achievements as a writer and as an explorer in French Guiana. The fruit of their joint work from 1895 to 1899 was six quarto volumes profusely illustrated by photographs which they had taken and by carefully executed charts of the various rivers which they had explored. While engaged in the exploration of the Trombetas, a tributary of the Amazon, Henri Coudreau was taken seriously ill, and, after a few days' struggle against the disease with which he was stricken, he expired in the depths of the forest primeval, where he was buried by his desolate and disconsolate widow. After such a calamity any other woman would have left the tropics at once and returned to her home and friends. Not so Mme. Coudreau. With matchless courage and determination she buried her grief in the work in which her husband had been so interested, and, after completing the unfinished survey, published the results of this expedition under the title _Voyage au Trombetas_. Having completed this work, she was engaged by the states of Para and Amazonas to explore a number of other rivers in the vast territory known as Amazonia. This commission involved the most arduous and dangerous kind of labor and was a task which few men would have been willing to undertake. It is doubtful if any other woman would have ventured on such an expedition, and it is quite certain that no other one could have been found that was so well equipped for this herculean undertaking or who would have carried it to a more successful issue. Mme. Coudreau was in the service of Amazonia, in the capacity of official explorer, from 1899 to 1906. Most of this time she spent in a canoe on the affluents of the Amazon, or in her tent in the dense forests under the equator. Her only companions were negroes, or Indians, or Brazilian halfbreeds who served her as porters, cooks and boatmen. Frequently they were in the forest wilds for many months at a time and far away from every vestige of civilized life. As it was impossible to take sufficient provisions with them to last them during the whole of their journey, they had to depend on wild fruits and such fish and game as they were able to secure. Often they were forced to live for weeks at a time on an unchanging diet of manioc and tapir meat.