NEW YORK — Investors dumped stocks and locked in profits yesterday after the glow of a week full of strong earnings reports faded.

The retreat came as cautious forecasts from railroads caused unease about the economy and a rising dollar pushed prices of commodities lower, which hurt materials and energy stocks. The Dow Jones industrial average fell 109 points to end the week with a modest loss.

Traders appeared eager to collect gains after earnings reports for the July-September quarter came in far stronger than forecast, which had pushed stock indexes up more than 6 percent in the three weeks leading into yesterday.