complicated, and takes rank by his extensive and accurate knowledge, as well as by his rare literary skill, with the highest names in his profession. That with his eminent medical acquirement he should have been able to deal adequately with so many other subjects as well, has long been a subject of perplexity. The cold censure of Quintilian, who refers to him slightly as "a man of moderate ability," may be principally aimed at the treatise on rhetoric, which formed a section of his encyclopedia. Columella, writing in the next age, speaks of him as one of the two leading authorities on agriculture; and he is also quoted as an authority of some value on military tactics. Yet we cannot suppose that the encyclopedist, however adequate his treatment of one or even more subjects, would not lay himself open in others to the censure of the specialist. It seems most reasonable to suppose that Celsus was one of a class which is not, after all, very uncommon--doctors of eminent knowledge and skill in their own art, who at the same time are men of wide culture and far-ranging practical interests. In striking contrast to Celsus as regards width of knowledge and literary skill, though no less famous in the history of his own art, is his contemporary, the celebrated architect Vitruvius Pollio. The ten books _De Architectura,_ dedicated to Augustus about the year 14 B.C., are the single important work on classical architecture which has come down from the ancient world, and, as such, have been the object of continuous professional study from the Renaissance down to the present day. But their reputation is not due to any literary merit. Vitruvius, however able as an architect, was a man of little general knowledge, and far from handy with his pen. His style varies between immoderate diffuseness and obscure brevity; sometimes he is barely intelligible, and he never writes with grace. Where in his introductory chapters or elsewhere he ventures beyond his strict province, his writing is that of a half-educated man who has lost simplicity without acquiring skill.