State banks and trust companies manage their reserve and surplus investment funds in substantially the same manner as national banks, using national banks in the reserve and central reserve cities as their reserve agents. State laws usually allow approved state banks and trust companies also to act as reserve agents for the banks and trust companies under their jurisdiction, but these approved banks are generally located in the reserve and central reserve cities, and themselves employ the national banks there located as their reserve agents, thus forming simply an additional conduit through which the reserve and surplus investment funds of state banks and trust companies reach the central money reservoirs administered by national banks in the central reserve cities. National banks in the reserve and central reserve cities are also clearing centers for the enormous volume of checks and drafts which the administration of the checking accounts of the banks and trust companies of the country bring into existence. They act as correspondents as well as reserve agents for these other banks and trust companies, and in this capacity collect out-of-town checks and drafts and conduct checking accounts for them. Within these cities, as well as in hundreds of others, clearing house associations conduct the local clearings and also act as agencies through which national and state banks and trust companies cooperate in the promotion of common interests. The center of the entire system is in New York City. The clearing house association of that city, consisting of over fifty national and state banks and trust companies, includes the banks the vaults of which constitute the central money reservoir of the country and which constitute the center of the country's clearing system. Through the New York subtreasury pass the greater part of the receipts and disbursements of the government, and the chief assay office in the country is located there. The New York stock exchange is our only stock and bond market of national scope, and consequently the investment center of the country.