For the nineteenth and the early twentieth century, the Philosophical Transactions was issued annually, and at times bi-annually, but there was never a fixed publishing date. The full volume was available once all the papers received, read, and sent to the printers during the Society’s session (November-November) were available. From 1887, however, separate papers were available for Fellows as soon as they were printed. In the 1930s the Transactions begins to be issued in several parts per year (but not quite monthly). It is not until 1990 [true?] that the Transactions becomes a monthly publication.