library was enriched with significant donations and with rare foreign language books from all over Europe. With the royal charter of 1866, the two libraries merged, and were administered as the "National Library of Greece". From 1877 to 1910, its director was Michael Deffner.

On 16 March 1888, the foundation stone for a new neoclassical marble building was laid. The building was financed by three Kefallonian-born brothers of the Diaspora,