During his stay in Berlin, Euler acquired the habit of writing memoir after
memoir, placing each when finished at the top of a pile of manuscripts. Whenever
material was needed to fill the Academy’s journal, the printers helped themselves
to a few papers from the top of the stack. As the height of the pile increased more
rapidly than the demands made upon it, memoirs at the bottom tended to remain in
place a long time. This explains how it happened that various papers of Euler were
published, when extensions and improvements of the material contained in them had
previously appeared in print under his name. We might also add that the manner in
which Euler made his work public contrasts sharply with the secrecy customary in
Fermat’s time.