Although it is not possible to give the value of any of the great public collections of Europe, some idea of their worth may be derived from that of collections formed by individuals. The collection of Dr. Hunter, bow at Glasgow, cost upwards of 21,0001., that of the late Mr. Thomas sold for 17,3041., that of the Earl of Pembroke for 5905/. 14s., and the late Lord Northwick's Greek and Roman collection realised 9138/. 14s.; that of the Duke of Devonshire, 6945/. 6s. 8d.
The rarity of ancient coins depends on various causes, but is prin cipally owing to the few struck from a peculiar die, owing to the poverty of certain States, of the short reigns of some princes, or the suppression of their coins by public authority. Of some Roman Emperors there are absolutely none in certain metals and sizes ; bronze coins of Otho, for example, were never struck by the Senate, and the coins of Caligula were called in and destroyed by the same body; hut in all cases preservation enhances in the highest degree the value of coins otherwise ordinary.
Ancient coins are discovered in the bosom of the earth, or in the bosom of rivers where they have been lost or hoarded by public or private misfortunes. Isolated discoveries are constantly being made by excavators, but sometimes they occur in great numbers ; 30,000 gold staters of Lysimachus were found in a river of the ancient Dacia, 30,000 silver denarii in 1760, at Brest, 4000 aurei at Hornoy, 12,000 pennies of William the Conqueror at Beaworth, and 7000 Saxon coins at Cuerdale, not to mention minor finds. They present different
appearances according to the locality ; gold under all circumstances retains its colour, but sometimes requires the removal of a crust of iron or other substances which adhere to it; silver is so oxydised as to present a grayish black colour, and for the types to be legible, it must be cleaned by lemon juice, citric acid, or acetic acid, and some use sal ammoniac. Bronzc and copper present a most varied appearance ; from the beds of rivers, such as the Thames, they have a yellow or brown patina, and only require removing from the matters which surround them. From volcanic soils they come with a bright turquoise blue or green patina, which must not be touched when it ie polished, and shows under its coat, like the varnish of a picture, all the contours of the type and legend. The yellow and brown patinas of other soils must be respected, but the green gritty rust which disfigures many copper coins may be successfully removed by placing the coins in 1 part of hydrochloric acid with 14 parts of water, watching the progress, and allowing them to remain a short time afterwards in ammonia. The use of the wire brush, of the knife or graver, may be also judiciously applied to cleaning brass coins.
The principal general works on the subject are (Hennin, Manuel de Numismatique Ancienne, 8vo, Paris, 1830; Grasset, Handbuch der alters Numisrnatile, 8vo, Lips. 1852-53; Werl hoff, Handbuch der Griechischen Nuntionatik, Svo, Haney., 1850; Bar thZlemy, Manuel de Numismatique, I6mo, Paris. [no date.] NUN. [Mosrecnisn.]