=Mortars.=--Mortars such as those referred to on p. 226 with accompanying pestles, were commonly in domestic use from the sixteenth to the eighteenth centuries. In later years they were employed chiefly in the preparation of drugs, but more recently they have been superseded by the modern way of preparing spices and other compounds by machinery. The form of the vessel may be described as an inverted bell, the substances therein being pounded or rubbed with the pestle. =Patina.=--A term expressive of the colour or encrustation which is imparted to works of art by age. It is used chiefly in reference to the beautiful green formation which covers ancient bronzes, shading from light green to deep brown. This crustation consists of basic copper carbonate, the result of exposure to the air. It is chiefly found on bronzes, the alloy of which is mostly of tin and very little zinc. The patina or patine is also the name given by the Romans to a shallow basin used for domestic purposes. =Pilgrims' Signs.=--The symbols or signs worn by pilgrims when visiting one or other of the famous shrines in this country in mediæval days were distinct from the crests or badges of wealthy patrons which were at one time worn pretty generally as indicating on whose service the journey they were making was being performed. Pilgrims' signs were worn on the outward journey chiefly as protective amulets; on the return journey mostly as proof of the pilgrimage, such signs being purchased at or near the shrines to which homage had been paid. The chief shrines in this country were those of St. Thomas à Becket at Canterbury, and Walsingham Priory in Norfolk, where Our Lady of Walsingham was held in high repute. =Weather-Vane.=--The vane denotes any flat surface attached to an axis and moved by the wind, usually applied to some elevated object for the purpose of telling which way the wind blows. A strip of metal cut to some fanciful form and placed upon a perpendicular axis around which it moves easily. I THE METAL AND ITS ALLOYS CHAPTER I THE METAL AND ITS ALLOYS Ancient bronze--The bronzes of Greece, Rome, and Eastern nations--Copper for enamels--The brass of commerce--Bell metal--The sources of copper--The making of brass--Copper as an alloy--The characteristics of metals.