Chemical Bank, the nation's sixth biggest, yesterday lowered its prime lending rate from 12 to 11 1/2 percent, the lowest that key business lending rate has been in more than two years.

But no other major bank followed Chemical's lead, and analysts said that the recent rapid decline in interest rates is about over unless the Federal Reserve Board takes new steps to ease monetary policy.

Sky-high interest rates for the last three years have helped to plunge the economy into the worst recession it has faced since the Great Depression and, despite a rapid decline in rates during the last three months, there is little evidence that the economy is moving into a recovery.

Yesterday the Commerce Department reported what might be a slight stirring in the economy. It said that new orders for manufacturer's durable goods climbed 0.2 percent in September after a 4.4 percent decline in August. But new orders, generally a signal of future production levels, fell 10.3 percent in the transportation industry, a signal that the automobile industry remains in the throes of a severe recession.

Automobile and related industries are still the nation's biggest employer.

William Sullivan, vice president of the Bank of New York, said that investors seem to believe that there is little chance the Federal Reserve will be able to take any further steps to ease its monetary policy. Interest rates in the so-called money markets moved up late yesterday afternoon after the Federal Reserve announced that the money supply -- the amount of cash and checking accounts in the economy--grew $3.2 billion last week.

The nation's central bank has said it will not try to fight temporary bulges in money growth by choking down on the availability of cash and credit in the economy. But Richard Peterson, chief economist for Chicago's Continental Illinois National Bank, said that yesterday's money supply jump came as "something of a shock."

Several weeks ago, the Federal Reserve apparently decided to ease its tight money policies, fearing that, if it did not, it could plunge the nation into an even more severe recession than the one it is experiencing. Interest rates, which fell sharply in July and August, tumbled again after reports of the change in Federal Reserve policy. But for the last two weeks, there have been no further declines in rates in the open market--where banks buy most of the funds they then lend to customers.

In late June, banks paid more than 15 percent to "buy" huge deposits for 90 days. For the last two weeks, those 90-day certificates of deposit have cost banks about 9 percent. During the same period, the prime rate--the interest rate on which banks base most of their business loan charges--has fallen from 16 1/2 percent to 12 percent at most banks and to 11 1/2 percent at Chemical. But despite the sharp decline in rates, interest costs for both companies and consumers remain high by historical standards.