In the performance of his duty Gen. Meade was inflexible, and would not stand any bluff or bluster from the Fenian leaders. On the contrary, he became very aggressive in compelling them to respect the laws and authority of the United States, and largely through his firmness and stern efforts the whole Fenian campaign was abandoned. ARREST OF PRESIDENT ROBERTS. On the 8th of June the United States Government caused the arrest of Col. W. B. Roberts, President of the Irish Republic, on a charge of conspiracy and violation of the Neutrality Act. He was brought before United States Commissioner Betts, at New York, and committed to jail pending a hearing of his case. From the quiet precincts of his contracted quarters he issued several proclamations, which teemed with gasconade and valiant promises, of which the following is a sample: Ludlow St. Jail, New York, June 11, 1866. To the Fenian Brotherhood and Irishmen of America: Friends and Countrymen,--The Irish people of America are again united in the cause of Irish independence and universal freedom. The cheer which arose from the Irish soldiers at Limestone Ridge as the English foe went fleeing before their avenging steel, had found a responsive echo in every Irish heart and made us one in love, purpose and resolve. We see, after ages of your oppression, the unquenchable desire for Irish independence blaze forth anew, and as it sweeps along the cities and prairies of this vast continent it gathers within its magic influence five millions of Irish hearts and twice five millions of friends of freedom and foes of despotism! Arise, then, my countrymen! Nerve yourselves for the struggle so nobly commenced. Cast aside every consideration that would darken the bright hopes of your enslaved countrymen. Be true to liberty, your country, and your God; and your native land, instead of being a lazar-house of slavery, will soon be the garden of freedom. Stand by the cause! Be not dismayed by obstacles you meet; you must surmount them, and you will. Let cowardice and ignorance desert and denounce you--what of that? The true men are still with us, and the struggle must not be abandoned, even though our soldiers should be compelled through the over-zeal of United States officers to abandon the present campaign. There is no turning back for us, my countrymen. Our movement must and will advance. Retrogression would entail certain infamy and bring a deeper stain upon your country and race, and it is as legitimate for you to attack English power in Canada as it was for England to attack France there, or France and America England. Remember, in union there is strength, and that Union which has been cemented by the blood of our gallant brothers must be eternal, and let that man be anathemized and banned who with lying lip or evil heart would dare to weaken or dissolve it. Be true to Ireland--steadfast in the right and undismayed by obstacles, and remember that--