Throughout the eighteenth century, two theories about the nature of light were in strong competition for acceptance. One theory, proposed by Dutch physicist and astronomer Christiaan Huygens (also spelled as Huyghens) during the seventeenth century asserted that light traveled as small waves (wave theory). Although the wave theory successfully accounted for many of the observed properties of light (e.g., interference), a discernible ether or medium of propagation thought necessary for the propagation of such waves continued to elude physicists. The second theory, propounded by English physicist Sir Isaac Newton in his 1687 work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) was that light consisted of a series of tiny particles or "corpuscles." The particle theory explained why light traveled in straight lines and why it did not need a medium to travel through. But several problems remained with this particle theory, including...