Heaviside's vector calculus, also known as vector analysis, was developed in the late 19th century as a way to simplify and unify the mathematical treatment of physical phenomena involving vectors, such as those described by James Clerk Maxwell's equations of electromagnetism. At the time, Maxwell's equations were typically expressed using quaternions, which are a type of mathematical notation that involves four complex numbers. The quaternion algebra, developed by James Clerk Maxwell and William Rowan Hamilton, was a more complex mathematical system that had been used to describe physical phenomena, but it was eventually replaced by vector calculus due to its relative simplicity and ease of use.
Quaternions involved complex numbers and required the use of four dimensions, which made them more difficult to work with and interpret. In contrast, vector calculus used a more familiar three-dimensional coordinate system and involved only familiar algebraic operations. Quaternions were found to be somewhat difficult to work with and interpret, especially for those who were not familiar with the notation.
In contrast, vector calculus provided a more intuitive and familiar way to represent and manipulate vectors, using familiar concepts such as magnitude and direction. As a result, vector calculus quickly gained widespread adoption and eventually replaced quaternions as the preferred method for expressing and solving problems involving vectors in physics and engineering. Heaviside's vector notation, which uses arrow notation to represent vectors and dot notation to represent scalars, is much easier to use and understand than quaternions, which are a type of mathematical notation that uses four-dimensional complex numbers.
While quaternions were primarily used in the study of electromagnetism, vector calculus could be used to represent any type of vector quantity, including displacement, velocity, acceleration, and force. This made it a more widely applicable tool for solving problems in many different fields of science and engineering.