classification. It holds that a statute which relates to persons or things as a class is a general law, while a statute which relates to particular persons or things of a class is special; that the necessity for classifica- tion is recognized in the constitution by the creation of courts on a basis of popula- tion and that classification is incident to legislation and necessary to the promotion of the public welfare; that the question is not whether it is authorized but whether it is expressly prohibited in the constitu- tion. It further holds that, for the purpose of taxation, real estate may be classified; as into timber lands, mineral lands, farm lands, etc., and that the act of 1874, which classifies cities according to their popula- tion. is constitutional. Where a federal statute has been taken from a state statute the settled construc- tion of the latter before the enactment of the former must be considered as having been adopted by congress; 171 U. S.-not reported. So also of the Interstate Com- merce Act, so far as it is based on Eng- lish acts; 145 U. S. 263. In a statute the words "it shall be lawful" are usually only permissive; they confer a faculty or power; but there may be something in the act imposing a duty to exercise such power, in which case the words become obligatory: 5 App Cas. 222. As to referring proposed legislation to a vote of the citizens, and as to the initiation of legislation by citizens, see REFERENDUM. See CONSTRUCTION; INTERPRETATION ; EX POST FACTO LAWS: CONSTITUTIONAL; CONSTITUTION; FOREIGN LAW; PUNCTUA- TION; PROVISO; OBSOLETE; REPEAL; RE- VISED STATUTES; STATUTES AT LARGE; RE- TROSPECTIVE LEGISLATION: PROMULGA- TION; PROCLAMATION: DIRECTORY IMPERA-