The dialogue _On the Face which appears on the Orb of the Moon_ is unique as showing the interest taken by men of good general education in scientific subjects in the first century of our era, and as evidence of the point to which the natural sciences had then attained. Professional science may be said to have been almost limited to the province of the mathematician and his congeners. Natural History was part of the general outfit of the ‘Philosophers’, and there was no idea of the ‘Conquest of Nature’ for the relief of man’s estate, unless by the engineer or the physician. With these limitations, the progress made may strike some modern readers as surprisingly great, and a good example may be found in the very precise knowledge of Hipparchus and Ptolemy of the delicate phenomena of the moon’s movements. We are tempted to ask whether, if Greeks had not settled these problems, which men of no other ancient race attacked scientifically, they would have been settled to this day. To come down to a humbler matter: if the properties of the conic sections had not been discovered by Apollonius and his predecessors, would they stand in their place, probably a modest one, on a modern syllabus, and, meanwhile, could the mechanical arts have progressed without them? And the conic sections are simple things compared with the lines, surfaces, and solids determined once for all by Archimedes. Archimedes was a mathematician by the grace of Nature, and an engineer by the order of a prince; and the conic sections themselves were examined, not from any practical interest in the cone, but because they were found to furnish instances of the curves which might facilitate the line of inquiry, suggested by Plato with such amazing foresight, as a half-way house towards a solution of Apollo’s problem.[14] Of course this can only be stated as a question—not a rhetorical question—and must be left on the knees of the gods. The general subject is discussed in D. Ruhnken’s admirable _De Graecia artium ac doctrinarum inventrice_, an inaugural lecture delivered at Leyden in 1757 (just thirty years after Newton’s death).