The object of the convention between the United States and Great Britain of the 19th of April, 1850, was to secure for the benefit of all nations the neutrality and the common use of any transit way or interoceanic communication across the Isthmus of Panama which might be opened within the limits of Central America. The pretensions subsequently asserted by Great Britain to dominion or control over territories in or near two of the routes, those of Nicaragua and Honduras, were deemed by the United States not merely incompatible with the main object of the treaty, but opposed even to its express stipulations. Occasion of controversy on this point has been removed by an additional treaty, which our minister at London has concluded, and which will be immediately submitted to the Senate for its consideration. Should the proposed supplemental arrangement be concurred in by all the parties to be affected by it, the objects contemplated by the original convention will have been fully attained. The treaty between the United States and Great Britain of the 5th of June, 1854, which went into effective operation in 1855, put an end to causes of irritation between the two countries, by securing to the United States the right of fishery on the coast of the British North American Provinces, with advantages equal to those enjoyed by British subjects. Besides the signal benefits of this treaty to a large class of our citizens engaged in a pursuit connected to no inconsiderable degree with our national prosperity and strength, it has had a favorable effect upon other interests in the provision it made for reciprocal freedom of trade between the United States and the British Provinces in America. The exports of domestic articles to those Provinces during the last year amounted to more than $22,000,000, exceeding those of the preceding year by nearly $7,000,000; and the imports therefrom during the same period amounted to more than twenty-one million, an increase of six million upon those of the previous year. The improved condition of this branch of our commerce is mainly attributable to the above-mentioned treaty. Provision was made in the first article of that treaty for a commission to designate the mouths of rivers to which the common right of fishery on the coast of the United States and the British Provinces was not to extend. This commission has been employed a part of two seasons, but without much progress in accomplishing the object for which it was instituted, in consequence of a serious difference of opinion between the commissioners, not only as to the precise point where the rivers terminate, but in many instances as to what constitutes a river. These difficulties, however, may be overcome by resort to the umpirage provided for by the treaty.