But in order to trace its progress up to this point, it is necessary to
go back to a far more remote period; nor, again, is it possible to
maintain strict chronological consistency in treating of the several
branches of the whole theme.

The books of which the most frequent use has been made in this first
portion of the work are Sismondi's 'Républiques Italiennes'; Muratori's
'Rerum Italicarum Scriptores'; the 'Archivio Storico Italiano'; the
seventh volume of Michelet's 'Histoire de France'; the seventh and
eighth volumes of Gregorovius' 'Geschichte der Stadt Rom'; Ferrari's
'Rivoluzioni d' Italia'; Alberi's series of Despatches; Gino Capponi's
'Storia della Repubblica di Firenze'; and Burckhardt's 'Cultur der
Renaissance in Italien.' To the last-named essay I must acknowledge
especial obligations. It fell under my notice when I had planned, and in
a great measure finished, my own work. But it would be difficult for me
to exaggerate the profit I have derived from the comparison of my
opinions with those of a writer so thorough in his learning and so
delicate in his perceptions as Jacob Burckhardt, or the amount I owe to
his acute and philosophical handling of the whole subject. I must also
express a special debt to Ferrari, many of whose views I have adopted in
the Chapter on 'Italian History.' With regard to the alterations
introduced into the substance of the book in this edition, it will be
enough to say that I have endeavored to bring each chapter up to the
level of present knowledge.

In conclusion, I once more ask indulgence for a volume which, though it
aims at a completeness of its own, is professedly but one part of a long
inquiry.