ramparts behind the thin walls of the ancient works, for the reception
of the new artillery. Moreover these walls were soon found inadequate to
resist the missiles of the besiegers, and it became necessary to replace
them by parapets of earth. In order to cover the retaining walls of
these parapets from the besieging batteries, it was also found to be
necessary to lower these walls as much as possible, and to raise the
counterscarps. The traces or plans of the works, however, received no
material change till about the close of the fifteenth century.

It is not known who first changed the ancient towers into bastions. Some
attribute it to an Italian, and with considerable show of reason, for a
bastion was built at Turin as early as 1461. Achmet Pacha, it is said,
fortified Otranto in this way, in 1480, but whether the system was
previously known among the Turks cannot be determined. Others attribute
the invention to Ziska, the celebrated leader of the Hussites. It is
most probable that the transition from the tower to the bastion was a
very gradual one, and that the change was perfected in several countries
at about the same time.

Fortifications, like other arts and sciences, greatly flourished in
Italy under the Medicis, and that country furnished Europe with its most
skilful engineers. Catharine of Medicis introduced into France many of
her countrymen, distinguished in this profession; among these may be
named Bellamat, Bephano, Costritio, Relogio, Vorganno, the two Marini,
Campi, and Hieronimo, who built several important places and directed
the sieges of others. These able foreigners were rivalled by some
distinguished French engineers, who laid the foundation of the "_corps
du Genie_" which has since become a school of military instruction for
the world. Among the early French engineers may be distinguished
Lafontaine De Serre, Feuquieres, and St. Remy. Pedro Navarro had been
appointed a member of this corps, but his attention was more specially
directed to mining, and we do not learn that he distinguished himself in
the construction of any fortification.

In Germany, in the beginning of the sixteenth century, Albert Durer
distinguished himself as a writer on fortification; his book is
remarkable as containing the germs of many of the improvements which
were made by those who followed him. This is the more to be wondered at
as he was not a professed engineer. After him followed Spekel, a native
of Strasburg, who