an instrument for the opening of locks. See Lock.

L. Molinus has a treatise of keys, De clavibus veterum, printed at Upsal: he derives the Latin name clavis from the Greek κλεις, κλείω, "I shut," or from the adverb κλαίω, "privately;" and adds, that the use of keys is yet unknown in some parts of Sweden.

The invention of keys is owing to one Theodore of Samos, according to Pliny and Polydore Virgil; but this must be a mistake, the use of keys having been known before the siege of Troy; mention even seems made of them in the 19th chapter of Genesis.

Molinus is of opinion, that keys at first only served for the tying certain knots, wherewith they anciently secured their doors; but the Laconic keys, he maintains, were nearly akin in use to our own; they consisted of three single teeth, and made the figure of an E; of which form there are still some to be seen in the cabinets of the curious.

There was another key called Κλαυστρα, made in the manner of a male screw; which had its corresponding female in a bolt affixed to the door. Key is hence become a general name for several things serving to shut up or close others. See the article Lock.

or Key-stone, of an Arch or Vault, is the last stone placed a-top thereof; which being wider and fuller at the top than bottom, wedges, as it were, and binds all the rest. The key is different in the different orders: in the Tuscan and Doric it is a plain stone only projecting; in the Ionic it is cut and waxed somewhat after the manner of consoles; in the Corinthian and Composite it is a console enriched with sculpture, foliages, &c.

Key is also used for ecclesiastical jurisdiction; particularly for the power of excommunicating and absolving. The Romanists say, the pope has the power of the keys, and can open and shut paradise as he pleases; grounding their opinion on that expression of Jesus Christ to Peter, "I will give thee the keys of the kingdom of heaven." In St Gregory we read that it was the custom heretofore for the popes to send a golden key to princes, wherein they included a little of the filings of St Peter's chains kept with a world of devotion at Rome; and that these keys were worn in the bosom, as being supposed to contain some wonderful virtues.

Key is also used for an index or explanation of a cipher. See Cipher.

KEYS of an Organ, Harpsichord, &c., those little pieces in the fore part of those instruments, by means whereof the jacks play so as to strike the strings. These are in number 28 or 29. In large organs there are several sets of the keys, some to play the secondary organ, some for the main body, some for the trumpet, and some for the echoing trumpet, &c.: in some there are but a part that play, and the rest are only for ornament. There are 20 slits in the large keys which make half notes. See the article Organ, &c.

in Music, a certain fundamental note or tone, to which the whole piece, be it in cantata, sonata, concerto, &c., is accommodated, and with which it usually begins but always ends.

or Quay, a long wharf, usually built of stone, by the side of a harbour or river, and having several storehouses for the convenience of lading and discharging merchant ships. It is accordingly furnished with polls and rings, whereby they are secured together with cranes, capstans, and other engines, to lift the goods into or out of the vessels which lie alongside.

The verb quayre, in old writers, according to Scaliger, signifies to keep in or restrain; and hence came our term key or quay, the ground where they are made being bound in with planks and polls.

Keys are also certain funken rocks lying near the surface of the water, particularly in the West Indies.