What do you mean by his being tried by the Senate?

The Senators take a solemn oath that they will carefully attend to the evidence that shall be brought before them, and according to that evidence adjudge the accused person innocent or guilty, as the case may be. The House of Representatives appoints some of their own Members to present this evidence before the Senate, and afterwards the accused person presents evidence in his defense; when both have been heard, the members of the Senate vote, that is, each one declares his opinion; and if two thirds of all the Senators who are present declare the accused person to be guilty, a guilty verdict is returned; if not, he is declared not to be guilty of the charges.