JTJBY FUSES DELBEET F. DUMASBrainerd, Minn, Dec. 11.—A jury declared Dr Delbert F. Dumas, mayor of Cass Lake, not guilty last night of the charge of arson In the third degree, In connection with the burning of the Bacon St Brown Building at Black Duck, Minn Dumas recently was convicted on the 1 charge of arson in the third degroe in connection with the alleged attempt to burn the poatofllce build* ing at Papoaky, Minn,