200 CHEMISTRY. 



including both this and malleability, for in either case la* 

 minse or leaves are formed. Gold is the most malleable of 

 all the metals. It has been beaten so thin as to require 

 nearly 300,000 leaves to make an inch in thickness if they 

 could be pressed into a solid mass. A leaf of this book equals 

 forty or more of such leaves in thickness. Some metals are 

 perfectly malleable when cold, as gold, silver, lead, and tin ; 

 while others, as iron and platinum, are only slightly malle- 

 able when cold, but very much so when heated. 



275. Ductility. This quality, named from the Latin word 

 duco, to lead or draw, is the capability of being drawn out 

 in the form of wire. It is very nearly allied to malleability. 

 Wires are made small by being drawn successively through 

 smooth conical holes in a steel plate, each hole being a little 

 smaller than the one through which the wire was previously 

 drawn. Dr. Wollaston made a gold wire so fine that one 

 hundred and sixty-one metres (five hundred and thirty 

 feet) of it weighed but sixty-four milligrammes (one grain), 

 and he succeeded in making a wire of platinum six times 

 as fine as this. This, then, is more ductile than gold, while 

 it is not by any means as malleable. 



276. Relations of the Metals to Heat. The melting points 

 of the metals, or the degrees of temperature at which they 

 melt, are very different. Thus it requires a much less de- 

 gree of heat to melt lead than it does iron ; and platinum 

 resists the heat of the hottest furnace, and can only be 

 melted in the flame of the oxyhydrogen blow-pipe or the 

 current of a galvanic battery. This metal stands at one 

 extreme in regard to fusibility, while mercury stands at the 

 other. So low is the degree of temperature at which this 

 latter melts, or, in other words, so little heat is required to 

 melt it, that it is in the solid state in no weather except 

 that of winter in the arctic regions. Many metals are quite 

 volatile that is, capable of being made to fly off in vapor 



