THE SENATE BANKING Committee is grinding slowly along with its consideration of G. William Miller, the prospective chairman of the Federal Reserve Board. Care and caution are important, for the job is one of the most influential in the government. But the investigation is developing a disquieting pattern. It is moving more and more uncertainly, emitting a trail of hints and whispered accusations for which neither the investigators nor anyone else seems to have any proof.

The committee has been at work for two months. It has developed a voluminous record. It now has an obligation to bring its researches to a conclusion, and to make up its mind. If it has evidence that in any degree casts a shadow on Mr. Miller, the time has come to state that case. If not, then the time has come to send the nomination to the Senate floor for a vote.

It would be unconscionable to leave the nomination in limbo because some of the senators seem to continue to nourish doubts and suspicions that the record of their own hearings cannot support. It would be even worse to use these doubts and suspicions as a reason to press Mr. Miller to withdraw his nomination and merely go away. He has answered under oath the questions put to him by the committee, and the members have produced no reason to think that he has misled them. The performance is beginning to suggest that these vague accusations about Mr. Miller's corporate past are, in some instances, only a screen or a surrogate for political objections to his opinions on future monetary policy.

The accusations revolve around tha sale of American combat helicopters to the Iranian armed forces. The helicopters were made by a subsidiary of Textron, Inc., the company that Mr. Miller heads. The sale was handled through an Iranian agent, a company called Air Taxi. The allegation is that the chief of the Iranian air force may have been a silent partner in Air Taxi at the time of the sale. That would have made the commission a bribe. The allegation is also that Mr. Miller knew, or should have known, about this relationship - if it existed. Mr. Miller denies each count and no one has contradicted him.

To bring up these kinds of questions in a nomination hearing is entirely proper. To go into them at length is necessary. But it is also necessary to pursue them to a conclusion, not merely to leave them hanging in mid-air with no visible means of support. It is grotesque to claim that these accusations cannot be answered and that the truth cannot be known - or, if ti can be discovered, that the process would take months of further investigation that neither the Federal Reserve nor the country can afford. On the contrary, the Banking Committee has a large and competent staff that has been hard at work since the end of December. Mr. Miller has appeared earlier before the committee, and he appears there again today. If there is a case against him, the committee has a responsibility to make it now. To leave the nomination in doubt would shortly begin to look like pure obstruction. And to ask Mr. Miller to solve the committee's problem by withdrawing his candidacy, in the absence of some disqualifying evidence of wrong-doing, would be grossly unfair.