Arrhenicum,[1749] too, is procured from the same sources. The best in quality is of the colour of the finest gold; that which is of a paler hue, or resembling sandarach, being less esteemed. There is a third kind also, the colour of which is a mixture of that of gold and of sandarach. The last two kinds are both of them scaly, but the other is dry and pure, and divides into delicate long veins.[1750] This substance has the same virtues as the one last mentioned, but is more active in its effects. Hence it is that it enters into the composition of cauteries and depilatory preparations. It is also used for the removal of hangnails, polypi of the nostrils, condylomatous tumours, and other kinds of excrescences. For the purpose of increasing its energies, it is heated in a new earthen vessel, until it changes its colour.[1751] SUMMARY.—Remedies, one hundred and fifty-eight. Facts, narratives, and observations, nine hundred and fifteen. ROMAN AUTHORS QUOTED.—L. Piso,[1752] Antias,[1753] Verrius,[1754] M. Varro,[1755] Cornelius Nepos,[1756] Messala,[1757] Rufus,[1758] the Poet Marsus,[1759] Bocchus,[1760] Julius Bassus[1761] who wrote in Greek on Medicine, Sextus Niger[1762] who did the same, Fabius Vestalis.[1763] FOREIGN AUTHORS QUOTED.—Democritus,[1764] Metrodorus[1765] of Scepsis, Menæchmus[1766] who wrote on the Toreutic art, Xenocrates[1767] who did the same, Antigonus[1768] who did the same, Duris[1769] who did the same, Heliodorus[1770] who wrote on the Votive Offerings of the Athenians, Pasiteles[1771] who wrote on Wonderful Works, Timæus[1772] who wrote on the Medicines derived from Metals, Nymphodorus,[1773] Iollas,[1774] Apollodorus,[1775] Andreas,[1776] Heraclides,[1777] Diagoras,[1778] Botrys,[1779] Archidemus,[1780] Dionysius,[1781] Aristogenes,[1782] Democles,[1783] Mnesides,[1784] Xenocrates[1785] the son of Zeno, Theomnestus.[1786] BOOK XXXV. AN ACCOUNT OF PAINTINGS AND COLOURS. CHAP. 1. (1.)—THE HONOUR ATTACHED TO PAINTING. I have now given at considerable length an account of the nature of metals, which constitute our wealth, and of the substances that are derived from them; so connecting my various subjects, as, at the same time, to describe an immense number of medicinal compositions which they furnish, the mysteries[1787] thrown upon them by the druggists, and the tedious minutiæ of the arts of chasing,[1788] and statuary,[1789] and of dyeing.[1790] It remains for me to describe the various kinds of earths and stones; a still more extensive series of subjects, each of which has been treated of, by the Greeks more particularly, in a great number of volumes. For my own part, I propose to employ a due degree of brevity, at the same time omitting nothing that is necessary or that is a product of Nature.