2. Judges and arbitrators enjoy a similar exemption with regard to matters before them. 3. Grand jurors, embracing even the clerk and prosecuting officer, cannot be examined on matters before them. 4. Transactions between the heads of Departments and their subordinate officers are treated as confidential. Plainly, the conferences of a Senator, in the discharge of his public duties, cannot be less protected. This rule is equally imperative with regard to witnesses who have confidentially communicated with a Senator. Here again I quote Professor Greenleaf, who quotes the eminent English judge of the close of the last century, Lord Chief-Justice Eyre, as follows:-- “There is a rule which has universally obtained on account of its importance to the public for the detection of crimes, that those persons who are the channel by means of which that detection is made should not be unnecessarily disclosed.”[27] Then the learned professor proceeds:-- “All were of opinion that all those questions which tend to the discovery of the channels by which the disclosure was made to the officers of justice were, upon the general principles of the convenience of public justice, to be suppressed; that all persons in that situation were protected from the discovery.”[28] These words are explicit, and nobody can question them. I am led to make these remarks and adduce these authorities because, perusing the testimony of Mr. Schurz, I find that he was interrogated on these very matters; and since I, too, am summoned as a witness, I desire to put on record my sense of the impropriety of such questions. It is important that they should not become a precedent. And here again I declare that I have nothing to conceal, nothing that I would not willingly give to the world under any examination and cross-examination; but I am unwilling to aid in the overthrow of a rule of law which stands on unquestionable grounds of public policy. Especially is it important in the Senate, where, without such protection, a tyrannical majority might deter a minority from originating unwelcome inquiries. * * * * * From these preliminaries I proceed to consider the competency of the present Committee. Requested as a Senator to appear before you, I deem it my duty to protest against the formation and constitution of the Committee as contrary to unquestionable requirements of Parliamentary Law; and I ask the Committee to receive this protest as my answer to their letter of invitation. I make this more readily because in my speech in the Senate, February 28, 1872, entitled “Reform and Purity in Government, Neutral Duties, Sale of Arms to Belligerent France,”[29] I have set forth what moved me to the inquiry, being grounds of suspicion, which, in my judgment, rendered the most searching inquiry by a committee friendly to inquiry absolutely necessary.