laid down by the founder. Few
listeners came, however, and at this juncture Cardan took a step which
serves to show how real was his devotion to the cause of true learning,
and how lightly he thought of an additional burden upon his own back, if
this cause could be helped forward thereby. Keenly as he enjoyed his
mathematical work, he laid a part of it aside when he perceived that the
benches before him were empty, and, by way of making his lectures more
attractive, he occasionally substituted geography for geometry, and
architecture for arithmetic. The necessary research and the preparation of
these lectures led naturally to the accumulation of a large mass of notes,
and as these increased under his hand Jerome began to consider whether it
might not be worth his while to use them in the composition of one or more
volumes. In 1535 he delivered as Plat lecturer his address, the _Encomium
Geometriae_, which he followed up shortly after by the publication of a
work, _Quindecim Libri Novae Geometriae_. But the most profitable labour of
these years was that which produced his first important book, _The
Practice of Arithmetic and Simple Mensuration_, which was published in
1539, a venture which brought to the author a reward of ten crowns.[84] It
was a well-planned and well-arranged manual, giving proof of the wide
erudition and sense of proportion possessed by the author. Besides dealing
with Arithmetic as understood by the modern school-boy, it discusses
certain astronomical operations, multiplication by memory, the mysteries
of the Roman and Ecclesiastical Calendars, and gives rules for the
solution of any problem arising from the terms of the same. It treats of
partnership in agriculture, the Mezzadria system still prevalent in
Tuscany and in other parts of Italy, of the value of money, of the strange
properties of certain numbers, and gives the first simple rules of Algebra
to serve as stepping-stones to the higher mathematics. It ends with
information as to house-rent, letters of credit and exchange, tables of
interest, games of chance, mensuration, and weights and measures. In an
appendix Cardan examines critically the work of Fra Luca Pacioli da Borgo,
an earlier writer on the subject, and points out numerous errors in the
same. The book from beginning to end shows signs of careful study and
compilation, and the fame which it brought to its author was well
deserved.

Cardan appended to the Arithmetic a printed notice w