“ There is considerable force in the suggestion that the word 'hereafter' is not to receive the weight which, in other circumstances, it ought to have. The question is, however, one as to the intention of Congress, and when we come to look at the provisions of the statute, as amended, we are convinced that Congress did not intend that the amendment should apply to cases where the bond had already been executed, the work done, the respective rights of the parties settled, and the cause of action already in existence. ”

“ It would follow necessarily that, if the full amount of the liability of the surety on the bond were insufficient to pay all the claims and demands, the provision that, after paying the full amount due the United States, the remainder only should be distributed pro rata among the interveners, would also be a substantive amendment, and not one of procedure. Hence counsel admits that the full amount which may be due the United States depends upon whether the bond was executed prior or subsequent to the amendment of the statute ”

“ It ought not to receive such a construction unless the words used are so clear, strong, and imperative that no other meaning can be annexed to them, or unless the intention of the legislature cannot be otherwise satisfied. ”