Half a century after Bacon's labours, Newton, with no help from Baconian methods discovered the law of gravitation, and with it the unity of sequences which pervade material creation. The cause of the slight progress of physical science whether before or immediately after Bacon formulated his method may be partly explained by the want of the material appliances for physical investigation. These in anything like their mechanical perfection of to-day are not much older than our present era. The agencies of glass, of alcohol, of microscopes and of other such appliances were as unknown to the physicists of Alexandria, of Athens, or of the Middle Ages as the electric wire itself. Where the subject matter, the heavenly bodies, the structure of the human frame, could be studied without elaborate machinery, the contemporaries or successors of the Ionian physicists who searched for the origin of all things in some single element, air, fire or water, seem rudely to have anticipated later discoveries. The Aristotelian philosophy and the rudiments of practical medicine, preserved together by Averrhoes, Avicenna, and the whole school of the Arabian thinkers of the twelfth and thirteenth centuries, descended in each other's company to the Italian schoolmen, and were delivered by them to English students. Thus, on the eve of the present century, the indestructibility of matter, however Protean the forms of its manifestations, had been ascertained by European chemists. The year of the Queen's accession was also that of the publication of Whewell's _History of the Inductive Sciences_. In this age, as in that of Bacon, great lawyers have taken a foremost place among enquirers into the nature of things. Lord Brougham did something to methodize, and more to popularize, the facts of science. A greater lawyer than Brougham, Sir William Grove, Justice of the Common Pleas first, Judge of the High Court of Justice afterwards, was also professor of experimental philosophy at the London Institution during the first decade of the reign. His discoveries with regard to the correlation of forces had not been entirely formulated when Dr Whewell's book appeared. Nor had Charles Darwin completed in his retirement at Down, in Kent, those researches which in 1859, gave the world _The Origin of Species_. This book, if the work of any single man ever did so, created an epoch, not in physical enquiry alone, but in every branch of human knowledge conducted on scientific principles.