Union of the Atlantic and Pacific --Dr. Cullen's plan for crossing the Isthmus of Panama by a Ship Canal has received the emphatic testimony in its favour of the veteran Alexander Von Humboldt.--"After having," he says, "laboured, in vain, during half a century, to prove the possibility of an Oceanic Canal, and to point out the Gulf of San Miguel and Cupica as the points most worthy of attention,--after having regretted, almost with bitterness, in the last edition of my 'Aspects of Nature,' that the employment of the means which the present state of our knowledge affords for obtaining precise measurements has been so long delayed,--I ought more than any one else, to be satisfied to see, at last, my hopes for so noble an enterprise revived. * * The undertaking is by no means above the intellectual and material power which civilized nations have attained to. The work should be one to last forever. It should not commence with a canal with locks, like the magnificent Caledonian Canal; it must be a really Oceanic Canal, without locks,--a free passage from sea to sea, across which the speed of the navigation will be modified, but not interrupted, by the difference in height and non-coincidence of the tides."