The Senatorial Districts are listed in "Members of the Texas Legislature 1846-1962," (Austin: Legislature of the State of Texas, 1962). This is a standard reference that should be in just about any major Texas library. Also, they are in James M. Day's "Senate Journal of the Ninth Legislature of the State of Texas, Regular Session, Nov. 4, 1861 - Jan. 14, 1862," (Austin: Texas State Library, 1963). These references give the district numbers and the counties that were in each.