Stocks sank in the final hour of trading Wednesday to finish with moderate losses. The Nasdaq fell 0.8%, while the S&P 500 and the Dow Jones industrial average dropped 0.7% each. The small-cap Russell 2000 tumbled 0.9% in the stock market today. Volume was lower on both the NYSE and Nasdaq exchange, according to preliminary data. Among Dow stocks, one was higher and 29 were lower. Poor performances by energy stocks weighed on the index.