concurring:
It has been said that wise men often change their opinions, and I wish to exemplify the fact that unwise men sometimes do the same thing. My views of the act of 1873 will be found expressed in the case of N. Y., N. H. & H. R. R. Co., decided February 25, 1918, ante, p. 222.
*317I do not think it can be judicially said that by the terms of section 4002 Revised Statutes any divisor was absolutely provided for. The Postmaster General was thereby directed to pay the railroads in proportion to the average weight of the mails carried, this average to be determined by weighing the same at least once every 4 years for not less than 90 working days. Of course this would imply some mathematical process which would involve some kind of a divisor. In any event the compensation paid should not exceed a definite sum named. This weighing, whether by the railroads as at first provided or under the supervision of the Postmaster General himself, was for his benefit alone and for the purpose of enabling him to exercise wise discretion in making contracts for the carriage of the mails. The details to be followed in the weighing in order to approximately obtain the average was entirely at the discretion and under the direction of the Postmaster General. It was for his information it was to be obtained, and it was for him alone to say how this was to be done. I can see why this long continued exercise of this discretion in a certain way should not be changed as to existing contracts because contracts are construed according to the intention of the parties to them when they were executed, and in this case these existing contracts were understood by both parties to have been executed in the light of the then existing method of obtaining average weights. But I do not see how a discretionary authority can ever be said to ripen into law by continued usage. Presumably the Postmaster General for a succession of years obtained such average weight in a way he thought best adapted to do justice to the different classes of railroads carrying the mails. This discretion seemed to be implied in the law.
Circumstances mentioned and described in the opinion of the Chief Justice became materially changed, and what was perhaps at one time a proper exercise of this discretion became improper, and a later Postmaster General in the exercise of the same power of discretion obtained this average weight in another way. In both instances it was a proper exercise of discretion which was once changed in effect, and *318can be changed again if reasonably within the statutes so as to affect the future contracts for the carriage of the mails.