An important report was made in the Senate, on the 30th of August, by Mr. Mason, of Virginia, from the Committee on Foreign Relations, upon the subject of the right of way across the Isthmus of Tehuantepec, granted to Don Jose de Garay, in March, 1842, by Santa Anna, then vested with supreme power as President of Mexico. The report, after mentioning this grant, and the stipulation contained in it that he, as well as any private individual or company succeeding him, native or foreign, should be protected in undisturbed enjoyment of all the concessions granted, states that on the 9th of February, 1843, a decree was issued by General Bravo, who had succeeded to the Presidency, recognizing and affirming this grant, and directing the departments of Oaxaca and Vera Cruz to put Garay in possession of the lands ceded to him by its provisions. On the 6th of October, 1843, Santa Anna, being restored to power, issued a further decree, directing the departments to furnish 300 convicts to be employed on the work; and by another decree of December 28, 1843, the time for commencing it was extended a year--until July 1, 1845. In November, 1846, General Salas, having, by the course of revolution, become invested with supreme power as Dictator, promulgated a decree, extending the time still further, namely, until November 5, 1848; and the work was actually commenced prior to that date. This is the history of the grant so long as it remained in the hands of Garay. During the year 1846 various contracts were entered into by which he transferred the grant, with all its rights and privileges, to Messrs. Manning and Mackintosh, subjects of Great Britain: and on the 28th of September, 1848, these contracts were formally recognized and consummated at the city of Mexico. On the 5th of February, 1848, this grant was assigned to Peter A. Hargous, a citizen of the United States, who subsequently entered into a contract to assign the same to certain citizens of New Orleans, on terms intended to secure the capital necessary to execute the work. In December, 1850, a party of engineers was sent out by the American assignees, to complete the necessary surveys--who continued so employed until the month of June following, when they were ordered by the Mexican government to discontinue the work and leave the country--a law having been passed by the Mexican Congress, and approved by the President, May 22, 1851, declaring the Garay grant to be null and void. Upon this statement of facts concerning the origin and history of the grant, the Report proceeds to show that its validity had been repeatedly recognized by the Mexican government. In 1846, President Herrera issued orders to prevent cutting mahogany from these lands. In 1847, while the treaty of peace was under discussion, Mr. Trist, by direction of our Government, offered a large sum for the right of way across the Isthmus; and was answered that "Mexico could not treat of