. . .Morgan county, and the Senator to be elected from Cook county and the Senator to be elected from Pike county, and the Senator to be elected from Macoupin County, and the Senator to be elected from Fulton county, and the Senators to be elected from the districts composed of the counties of LaSalle, Iroquois, M^cLean, Macon, Calhoun, Greene, Putnam, Peoria[,] Madison[,] S^t Clair, Monroe, Hancock, M^cDonough, Warren[,] Knox[,] Henry[,] Coles[,] Clark[,] Washington and Perry shall proceed to divide by Lot their said number into two classes, the first class of which shall serve until the expiration of two years from the first monday of August, 1836; and the second class shall serve four years from the first Monday in August 1836; and in case of any vacancy occuring in any of the aforesaid offices, the same shall be filled in the manner prescribed by Law for filling vacancies in the General Assembly.