An exploratory journey in the isthmus of Panama has recently been made by M. Hillert, which has resulted in adding much important information to our previous knowledge of the country. It is known that there have been many surveys of the isthmus, with the view of opening a water communication between the oceans on either side. Such was the primary object of Mr. Hillert, who, it appears has also made enquiries as to the practicability of making a rail road across it. His observations on the junction of the two oceans by means of a canal have appeared in the bulletin of the Geographical Society of Paris for 1846, (pp. 306 and 389), together with various letters from him on other subjects which attracted his attention. Among other things Mr. Hillert has made known a most valuable anti-venomous plant, the guaco, a creeping plant, which abounds in the forest of the Isthmus, the virtues of which were made known to him by the Indians. After rubbing the hands with the leaves of this plant, a person may handle scorpions and venomous insects with impunity, and mosquitoes after sucking the blood of those who had taken it inwardly died instantly. The geology and botany of the country received particular attention. M. Hillert proposes to introduce several of the most useful plants and vegetables into the French dominions in Senegal or Algeria, among them the plant from which the Panama hats are made. So valuable are the labors of this gentleman considered, that the French commission has awarded him the Orleans prize, for having introduced into France the most useful improvement in agriculture. Some ancient monumental edifices were discovered in the Isthmus, not far from the river Atrato, and others near the mines of Cano; besides these an ancient canal cut through the solid rock in the interval which separates the rivers Atrato and Darien. NOTE.--The following list embraces all the books relating to Oregon, California, and Mexico, printed during the last two years. Narrative of the exploring expedition to the Rocky Mountains, in the year 1842, and to Oregon and North California, in the years 1843-4, by Capt. J.C. Fremont of the Topographical Engineers, under the orders of Col. J.J. Abert, 8vo. Washington, 1846. Exploration du Territoire de l'Oregon, des Californies, et de la Mer Vermeille, executée pendant les années 1840, 41 et 42, par M. Duflot de Mofras, Attaché à la Légation de France à Mexico. 2 vols. 8vo. and folio atlas of maps and plates. Paris, 1845. The Oregon Territory, claims thereto, of England and America considered, its condition and prospects. By Alexander Simpson, Esq. 8vo. London, 1846. The Oregon Territory, a geographical and physical account of that country and its inhabitants. By Rev. C.G. Nicholay. 18mo. London, 1846.