The History of Discoveries respecting LIGHT and COLOURS published in 1772 was a more difficult task, nor did it meet with equal encouragement. Sir Isaac Newton’s important labours in this branch of science, could not be fully comprehended without a portion of mathematical knowledge not even then so common as formerly, among the philosophers of the day. Mathematical studies seem to have in themselves very little to interest, compared with other literary pursuits; although by long attention and habit, that interest may be excited and kept up. It was about this time that the popular phenomena of chemistry and electricity more decidedly took their stand in the field of science, and irresistably seized hold on the attention of the world: phenomena, highly amusing in themselves, strongly attractive from their novelty, of evident and immediate application, and that promised an incalculable harvest of honourable and useful discovery, to such as would become their votaries. Little had been done in this department of philosophy, little previous knowledge was required to comprehend all that was known, and those who were unable to read a page of Sir Isaac Newton with profit, could easily mix an acid and an alkali, or turn the wheel of an electrical apparatus. By this time too, it had been discovered, that there were other powers in nature that must be called in to explain appearances, which the mechanical and corpuscular philosophy had endeavoured to elucidate in vain. Such were magnetism, electricity and chemistry. It began to be found out, that the science of calculation, was but an aukward handmaid to their sister branches of natural philosophy, while physiology, laughed outright at the clumsy addresses of her mathematical admirers, from Borelli to Keill.