An attempt was made on Tuesday night, we are told, to commit a rob* bery on Samuel Mitchell, a mulatto fromVernon who was temporarily here. He was in the barber shop of Silas Case, a colored man. He bad some $400 in his possession. The lights were suddenlyblown out, when he was seized and ^ strangled, but his cries of murder bro't persons to his rescue. e omit tho names of the assaulting parties atpresent