Yes Wellie, the NYSE does have
"circuit breakers" for if the market is to hot or cold.
A market can be suspended trading for a few hours or for the day. If trading is suspended for a day, the market, by law, must open the following day. The circuit breaker is a % of the market medium from the previous day.
So lets say that the circuit breaker is 10% and the DJIA medium from yesterday was 15,900. Once the market dropped 1,590 points in one day, the circuit breaker would open and trading could be suspended for hours or closed for the day.
But remember, if trading is suspended for the day the market must open the next day, albeit at 14,310 (15,900 correction x 10%= 1,590 - 15,900=14,310). This procedure allows for a "cooling off period."
With that all said, the market could loose 10% a day for X days. So in theory it would take 4-5 days to reach a 40% correction if the circuit breaker was 10%. I am sure The Fed would jump in at some point to spend your dollars to shore up the market, e.g. make buys.
Just some food for thought.