Harvard College Observatory Circulars
The Harvard College Observatory Circulars (HCOCs) were
begun in 1895 to announce information about astronomical
phenomena requiring prompt dissemination. In 1898, the
College Observatory Bulletins (HCOBs)
replaced the HCOCs for rapid postal mailing of such
astronomical news concerning new discoveries of comets, novae, etc.,
while the HCOCs continued for many years in expanded form.
The HCOCs have been scanned in by the SAO's ADS
service and are available at the ADS website
(but note that they are merely Circulars with no volume numbers,
despite what ADS says).