An abridgement of the authors original Treatise on Natural Philosophy , this work was designed to be accessible to students with a basic knowledge of algebra, geometry, and trigonometry. As such it is a book that non-specialists can still appreciate. Like Isaac Newton’s great summation of ‘natural philosophy’ in the late 17th century (The Principia Mathematica ), this work remains of interest to historians of science because it represented a similar summation of the grand synthesis that scientists, building upon Newton’s work, envisioned at the end of the 19th century. Not long after its publication, however, was the advent of relativity and quantum physics, which considerably changed and enlarged the picture of the natural world as conceived by earlier generations of scientists.