When any action is commenced to determine adverse claims, publication of the summons may be made and service upon parties outside of the State and unknown claimants obtained in the following manner. When the sheriff of the county in which the action is brought shall have duly determined that the defendant cannot be found therein, and an affidavit of the plaintiff or his attorney shall have been filed with the clerk stating that a cause of action exists to determine adverse claims to certain property within the county, and that he believes the defendant or defendants, naming them, is not a resident of the State or cannot be found therein and either (a) that he has mailed a copy of the summons, by registered mail, to the defendant at his place of residence or (b) that such residence is not known to him, service of the summons may be made upon the defendant by three weeks’ public notice thereof in the manner provided by law for publication of summons in civil actions. Personal service of such summons without the State, made after order for publication, proved by the affidavit of the person making such service made before an authorized officer having a seal, shall have the same effect as the publication of the summons herein provided.