Alexander's headquarters included a historical archives unit. Of lowest rank were clerks whose task it was to collect information about the day's operations and events, probably in the form of written notes. This information was reported to an officer in charge of keeping the
ephemerides, “Day Journal,” a record of the army's doings similar to a ship's log. For most of Alexander's expedition, the officer was Diodotus of Erythrae, who remained of such low rank that he is only mentioned once anywhere. His commanding officer,
Eumenes, was a Hetairos, a trusted companion of Alexander. Once the Day Journal was completed for the day, it was made available to the army's official historian,
Callisthenes, a grand-nephew of
Aristotle. He and Alexander were both peripatetics. Callisthenes was not the only officer to take an interest in the Day Journal.
Cleitarchus was writing a history, and so was
Ptolemy. The two were together in Alexandria, Egypt, after the
Partition of Babylon. The next generation of historians, such as
Timagenes and
Arrian, were to make extensive use of the Day Journal, as well as of the histories of Callisthenes and Ptolemy. Callisthenes came to a bad end through his resistance to adopting Persian customs promulgated by Alexander as part of his programme for building a multi-ethnic state. Some of the journal was lost by him on the Indus River. Eumenes switched to being an infantry officer after the death of Alexander. In the Partition, he went with Perdiccas, to share his evil fate. The Day Journal was continued, presumably under Diodotus and the clerks. Strattis of Olynthus subsequently wrote a work about it. Despite Alexander's care, the Day Journal is missing without a trace except for the works of the writers who used it. For the most part they went with Ptolemy, the ultimate victor in the
Wars of the Diadochi. He did the most also to perpetuate the traditions of the
Lyceum, Aristotle's school, building a library and a research center grander than any that had gone before, and personally inviting any peripatetics that he encountered during his maritime hegemony. He went out of his way and spared no expense to obtain the best engineers, mathematicians and philosophers. It is only because of his proactive efforts and those of his librarians that so many ancient writings have survived. Later, Curtius could have found his primary sources nowhere else. The library was subsequently lost, but it had done its work in disseminating Greek scholarship throughout the Graeco-Roman world. == Author and dating ==