In our first article we showed the Progress of Slavery, from its first beginning on the Virginia shore to its present gigantic limits ; and its probable extensiÃ³n, as predicted by Mr. Wise of Virginio, from the Atlnntic to the Pacific ocean, unless it should be checked by a general league ngainsl it. In the two following articles we considered the number, character, and principies oÃ the band of Slaveholders who have seized the reinsof our Government, and are using all its mighty and noble enorgies for the aggrandizement of themselves and their institution. We will now consider the mcans by which this overshadowing ascendency has been gained, and is held. The Federal Representation. By the Constitution, the free people of the Slave Slates have the same representation in Congress that is allowed to the Free States. This is as t should be. All free persons should be represented. But the Constitution goes further. Three fifths of all slave are represented in Congress, in almost every instance, by men who are personally slaveholders. This operates, of course, asa bounty on slaveholding, and builds up that class of men by ofFiring to them political power just in proportion to their number of slaves. A rich man can elect himself to Congress, or lo most of the State Legislatures, f he owns slaves enough. Suppose John Jacob Astor should buy up all the land composing this Congressional District, he would be no nearer to a eeat in Congress than he was before, because he is still to be voted for by the freemen of the district. Now suppose he buys up a Congressional district in South Carolina, and makes one vast plantation of it. By putting on to his premises enough, he could become a member of Congress merely by the nuviber of his slaves, without the votes of any white men. The principie operates all through the South : and as the three-fifths principie prevails extensively in appointing the members of the Legislatures, it is obvious that to own slaves is one important step towards political preferment. By the apportionment of 1830, when the number of slaves was less than two millions, the number of Ropresentatives in Congress was 242, of which the Free States elected 142, and the Slave States 100. But by their number of free in habitants, the Slave States were entitled to only 75 Representativos. Th'is twenty-five Southern represented mere property - a property valued by Mr. Clay at Twelve Hundred i Millions of dollars, lt is easy to see how these twenty-five votes, on every question belween Slavery and Freedom, cou!d be made to turn the ecale for the slaveholding interest. This interest hns ahvays been strong in the Senate : for every member ofthat House f rom the Slave States, is, and has been for tho last generation, personally a slavcholdcr. We have the authority of J. Q. Adams for this statement. It is obvious that the greater the number oÃ' Representatives, the less proportionately would be the power of the Senate : and the smaller the representaron in the popu lar branchjthe less chance that the reform snirit of the people would find means for ulterance and agitation. Mencp, in fixing the apportionment of 1840, the number of the House was reduced, by the manogement of the Senate, from242 to the present number, 228, (including the new Slates). In fixing the ratio of representation, the House adopted that of 50,179. This would have given a House of 306 members, and the Free States a majority of 68. But as it might bÃ¶ diiÃ¯icultj for the slaveholders to manage so large a majority, the ratio was altered by the Senate to 70,080. This reduced the House to 223, and brought down the majority of tho free States to 47 members. This effect was noticed at the time, by some northern papers, but the slaveholders in this, as in most things, had their own way. The correspondent of the New York Herald said - "The Senate apportionment has robbed the Norlh of al least one quarter of its practical infiuence in the Union, when regarded in its full exlent." After the apportionment had been made, it was discovered that the effect of the odd number, 680. was to deprive the four great States of the North. Ohio, Pennsylvania, New York and Massachusetts, of one member each, while it worked no disadvantage to any slaveholding State. This had been privately cyphered out by some of the slaveholding members, and Slavery has the advantage of the trick for ten years. The total number of slaves in 1840, as reported in the Madisonian, was 2,483, - 535. Deduct two fifths from t his number, and you have left 1,490,121 as the federal number. Divide this by 70,680, the ratio of representation for each member, and you have twenty-one members, probably every one a slavcholdcr, sitting in the House as representatives of slave property. Now, when you consider the tenure by which these members hold their seats, and the factthat thegrcatcr part of the most important controverted questions are decided in the House by nless majority than 21, you cannot avoid seeingthat their influence, in a long series of years, is tremendous. Atlhis very day, it aÃ¯Ã¯ects every family in the country. Had it not been for the opposition of these members, all letter postage could have been reduced to five cents. These SlavÃ©ry-represeruing votes carried the Missouri question - anncxcd Texas, and are prepnritg to annex more Slave Stntes in the Mexican provinces of California and Santa Fe. The Electoral vote. This inequality is carried into the Presidential as well as the Congrossfonal elections. Thus, Massachusetts, with 729,030 white population has 12 electors of President : Kentucky, with only 587,542 whitcs, has the same number. Michigan, wilh 211,560 whites,. has 5 electors: Louisiana,with a white population of only 153,983, or one quarter less, bas tx electors. Mississippi, with only 179,074 whites, has also six. Massachusetts, with 729,030 whiteSjhas 12 electors : Virginia, with 740,968, has seventcen : Maine has 500,438 whites and 9 electors : N. Carolina, with only 484.807 whites, hasoleven electors. Texas, with a free population of probably not more than 75,000, bas two representatives and four electors. lts slaves have not yet been oflÃ¯cially counted, but are certainly reckoned, in this representation, on a liberal scale. One consequence of this "federal number" system is tho inequality of the power of voters in the respective sections. - Repuhlicanism requires that every man of full age permanently resident of the country, should have an equal voico in the election of rulers. This ia far from being the case. For instance, 26,365 votes in Louisiana elccted six electors : while 69,673 in Connecticut elected only the same number. The federal ratio being the standard, in the district where there are most a mere hand ful of votes elect Congressmen and electors of President. Thus one vote at the South may have two or three, times as much power as a vote of the Free States. The average number of votes for each representative in 1840 was, in Michigan, 14r 797 : while in Virginia, it was but 5,753, and in South Carolina 6,374. Thus a voter in Virginia or South Carolina has moro than twice the amount of power that tho Michigan votor wields. Each Louisiana voter has three times as much. In tho election of 1840, each northern elector represented 10,708 voters : each slaveholding one, 6,465.