JEROME CARDAN 71 



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. 1 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 astrono- 

 mical operations, multiplication by memory, the mys- 

 teries 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, mensura- 

 tion, 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 



1 It was published at Milan by Bernardo Caluschio, with a dedi- 

 cation dated 1537 to Francesco Gaddi, a descendant of the famous 

 family of Florence. This man was Prior of the Augustinian Canons 

 in Milan, and a great personage, but ill fortune seems to have over- 

 taken him in his latter days. Cardan writes (Opera, torn. i. p. 107) : 

 " qui cum mihi amicus esset dum floreret, Rexque cognomine ob 

 potentiam appellaretur, conjectus in carcerem, miser vitam ibi, ne 

 dicam crudeliter, finivit : nam per quindecim dies in profundissima 

 gorgyne fuit, ut vivus sepeliretur." 



