THE REASONS WHY REBEL AGENTS WERE SENT TO CANADA, AND THEIR DOINGS--VARIOUS PLOTS OF MISCHIEF, HARRASSING, PILLAGING, &c.--THE WATCHWORD OF THE REBELS IN CANADA. The United States armies being continually pressed forward, step by step, towards the heart of the Confederacy, occupying more and more of the soil from which their commissary was but illy and scantily supplied, together with a desire on the part of the Southern people, to let the people of the North see what invasion meant, to make them feel and see the destruction and desolation following our army of invasion, determined the Richmond government, in 1863, to send its agents to the Canadas, well supplied with money, to endeavor to foment discord, and to intensify the dissatisfaction already existing in certain political circles, with the government, to such an extent that it could be made available for their own uses and purposes. Knowing that thousands of their soldiers were confined at Johnston's Island, and Camp Douglas near Chicago, almost within twelve hours' travel of Canada, it was the great object of the rebel government to release those prisoners of war, and in the mean time having stirred up and excited a formidable conspiracy in the North, particularly in the North-West, having in view the subversion of the government, and the securing of material aid and assistance to the rebels, and those rebel prisoners being released through the instrumentality of the rebels from Canada and those of the Northern sympathizers who could be induced to join in the expeditions for that purpose, the conspiracy was to culminate all over the North--but principally in Illinois, Ohio, Indiana, Kentucky, Missouri and New York, and effect the release of the prisoners of war confined in the various prisons in those States. The prisoners at all these places being released, were to form a nucleus around which all the dissatisfied people of the Northern States could rally, and endeavor to maintain themselves and their cause here in the North, and by rallying in formidable numbers, to cause the withdrawal of so many troops from the field in front, to establish peace at home, that it would materially change the whole character of the war, and remove the seat of war from the cotton States to the Northern States--Kentucky, Tennessee and Missouri. Upon the withdrawal of the troops in any considerable numbers from the front, was to follow the advance of the rebel armies into Kentucky, Tennessee and Missouri.