In the microcosm of one session, Thursday was an example of what has happened in the market in the period from last October's lows, from the beginning of the year and since the March lows: The Nasdaq Composite performed best, trailed by the S&P 500, with the Dow Jones Industrial Average lagging furthest behind. For the second day running, major averages were unable to sustain a midmorning peak. The afternoon weakness proved most pronounced for the Dow, which finished down 0.9% to 8711.18 after trading as high as 8862.58 and as low as 8679.60. The S&P 500 ended off 0.4% to 949.64 vs. its intraday high of 962.08. The Nasdaq fell from its apex of 1591.30 but closed up 0.7% to 1574.95. Big Board volume approached 1.7 billion shares, the highest this week and a bit disconcerting (to bulls), given the Dow's performance. At about 2.2 billion shares, Nasdaq trading exceeded 2 billion shares for a second straight day. Weakness in 3M ( MMM), Caterpillar ( CAT) and rumors of accounting concerns at American Express ( AXP) weighed most heavily on the blue-chip index, which may have a period of negative performance to follow its recent underperformance. "All of our intermediate-term indicators suggest we're still in the early stages of a substantial uptrend for small- and mid-cap stocks," said Paul Desmond, president of Lowry's Reports. But "short term, we're getting some divergences that make us feel we're headed toward a correction bigger than any to date in this uptrend, and big-caps could get hit hard," perhaps by 10% to 12%. Those divergences include the Dow being unable to get above its January highs even as other major averages surpassed theirs. Meanwhile, Lowry's measure of mid-cap stocks "has blown through" its comparable level, Desmond said. "Perhaps we'll see big-cap stocks run into real resistance, but I don't see any for small- and mid-caps" on the Big Board. The same holds for the Nasdaq, he continued, suggesting that "big-cap tech names are acting sluggish, whereas smaller-caps are acting strong."