The emission measure of the quiet corona, defined by the plasma hotter than one million degrees, is fluctuating in nearly every1900&hthinsp;km×1900&hthinsp;kmpixel observed by EIT on SoHO. In the average, the larger the emission measure in a pixel, the more it fluctuates. Increases in emission measure constitute a major energy input into the corona, suggesting that the lower corona is not just heated, but continuously replenished by chromospheric material heated to coronal temperatures. ©1999 American Institute of Physics.