There are slides devoted to this topic: Lecture 2, pp. 37-43

Websites

Read “The Pascaline of Blaise Pascal,” on the History of Computing site, to learn the story behind the Pascaline’s development, followed by a detailed explanation of how the machine performs addition, subtraction, multiplication, and division.

For another description and explanation of the Pascaline’s workings, read the “About Pascaline” page.

Other Media

Watch “How the Pascaline Works” for a clear, animated explanation for how the Pascaline performed addition and subtraction. This animation also goes into detailed examination of how the machine’s gears interact.

Books

Ifrah, Georges, The Universal History of Computing, 122-125