Dow Theory followers are getting plenty to whet their appetite as to whether current trends are signaling something more for the market.

Two principal trends that Dow theorists watch are the performance of the Dow transports, and the strength of volume on strong up or down days. Dow Theory follows six principal tenets and examines them in the context of market behavior, over both short and longer terms.

Indeed, the transports outpaced the July rally, gaining more than 10 percent as the Dow Jones Industrial Average itself gained 7.1 percent.

But as August has come and the market has dropped, the transports are off 4.2 percent while the broader index is down just 1.1 percent. (Does it matter? Not according to Andrew Busch.)

"Transports may well be pointing toward something deeper than a mild correction here," says Art Hogan, managing director at Jefferies in Boston. "Market participants are clearly showing they're nervous by piling into a very crowded Treasury trade."

Volume, too, has been indicating a possible Dow Theory trend. Volume has been sharply higher on down days for the blue-chip index, rising nearly 20 percent during the market's selloff Wednesday when the Dow fell 2.6 percent.

But whether the volume is making a clear indication may be determined only in September, when investors return from vacation and bring daily activity closer to normal levels. Even with the sharp uptick in volume Wednesday, it was still more than 10 percent below its daily average.

"Statistically, there's always lower volume on down days," Hogan says. "It's hard to say that's confirming the trend."