The number of primary sources has multiplied by a large factor. Letters have become a major source for both personal and professional life. Sometimes (as in Gauss' case) a diary. Or also (as in Gauss' case) a large collection of scribbled notes. Publication is a more formal and more permanent record. The problem now is, how to reduce the available material to something comprehensible? So the job of an historian is easier in some ways, and much more difficult in others.