I approach the termination of a comprehensive and hazardous undertaking. More than two thousand years have been passed in review, from the earliest state of intellectual cultivation among the nations who dwelt round the basin of the Mediterranean and in the fertile river districts of Western Asia, to a period the views and feelings of which pass by almost imperceptible shades into those of our own age. I have sought to present the history of the gradually developed knowledge and recognition of the Universe as a whole, in seven distinctly marked sections, or as it were in a series of as many distinct pictures. Whether any measure of success has attended this attempt to maintain in their due subordination the mass of accumulated materials, to seize the character of the leading epochs, and to mark the paths in which ideas and civilisation have been conducted onwards, cannot be determined by him who, with a just mistrust of his remaining powers, knows only that the type of so great an undertaking has floated in clear, though general, outlines before his mental eye.

In the early part of the section occupied by the epoch of the Arabians, in beginning to describe the powerful influence exerted by the blending of a foreign element with European civilisation, I determined the period from which the history of the Cosmos becomes coincident with that of the physical sciences.