“ We cannot believe that Congress intended to give immunity to those who for the period named in the statute might be able to conceal their fraudulent action from the knowledge of the agents of the government. We are aware of no good reason why the rule, now almost universal, that statutes of limitations to set aside fraudulent transactions shall not begin to run until the discovery of the fraud, should not apply in favor of the government as well as a private individual. ”

“ The statute of limitations was mainly intended to suppress fraud, by preventing fraudulent and unjust claims from starting up at great distances of time, when the evidence might no longer be within the reach of the other party, by which they could be repelled. It ought not, then, to be so construed, as to become an instrument to encourage fraud, if it admits of any other reasonable interpretation; and cases of fraud, therefore, form an implied exception, to be acted upon by courts of law and equity, according to the nature of their respective jurisdictions. ”

“ It is not our belief that Congress intended that the government should be deprived of title to public lands by those who add to the fraud by which they were obtained artifices which enabled them to conceal the fraudulent manner in which they were secured until the action was supposed to be barred by the lapse of six years. ”