Mathematical Treasure: Two Works of Joseph Fenn

In 1772, Joseph Fenn published The Complete Accountant: Being a System of Arithmetic, Both Theoretical and Practical. The text was employed at his school in Dublin.

The first page of the text begins with a discussion of computations, numbers and units:

A plate from the text illustrating solids:

In 1769, Fenn published an English version of Euclid’s Elements. Below is Proposition 31 from Book 6, which generalizes the Pythagorean Theorem (Proposition 47 of Book 1) from area of squares to areas of any similar plane figures.

The historian of mathematics Florian Cajori noted that Fenn's work contains a statement similar to Playfair’s Axiom.  Consider the footnote on page 44 shown below:

The first four images were obtained from the Joseph L. Rousseau Collection of Mathematics and Ciphering Books, Millersville University Library, and the fifth image from the HathiTrust Digital Library.

Index to Mathematical Treasures