S&P 500, Dow Gain Ground, But Trade Slips

Oil stocks helped lead the major NYSE indexes higher Monday. The S&P 500 added 0.5%, while the Dow industrials tacked on 0.7%.

But volume was lighter than it had been on Friday. Normally, you like to see volume increase on days the stock market heads higher.

Oil drilling companies climbed on word of a merger between industry heavyweights Transocean RIG and GlobalSantaFe GSF. The resulting company will be the largest in the oil drilling sector.

Transocean jumped 5.99 to a record 115.96 on volume that was more than two times heavier than usual. GlobalSantaFe also hit an all-time high, gapping up to add 3.59 to 78.33 on heavy trading.

The Transocean-GlobalSantaFe deal sparked speculation of further consolidation in the industry and helped give other drillers a boost.

One such stock was Atwood Oceanics ATW, which shot up 5.46 to 74.36 as volume more than tripled. The stock has repeatedly found support along its 10-week moving average in recent months.

Fellow drilling company Ensco International ESV -- also fresh off a visit to its 10-week average line -- gapped up 2.64 to 65.90. Volume swelled to more than two times the usual level.

Other stocks gaining ground included New Oriental Education & Technology Group EDU, which climbed 3.65 to 58.66. The China-based commercial school is scheduled to release earnings Tuesday morning.

Excel Maritime Carriers EXM added 3.20 to finish at 40.62, its highest level since October 2004 . The stock has been climbing since it cleared a base earlier this month.