In the course of a recent prolonged residence in Tuscany and the Carrara Marble District, I had occasion to become well-acquainted with the Maremma hills and the islands composing the Tuscan Archipelago; and as I propose to revisit those islands at an early date with a view to more closely examine certain phenomena relating to the eruptive and metamorphic series more especially of Elba, it may not be out of place if, in the meantime, I give a rapid preliminary sketch of the leading geological and petrological features of that archipelago as a whole.