284 NEW ZEALAND NATURE-STUDY BOOK 
the whole mass is allowed to cool gradually. Usually, 
about three weeks are employed in the process ; one to 
raise the mass to the required temperature ; one to keep it 
at this temperature, and one to cool it. 
LEAD. 
Pieces of the metal, as well as specimens of Lead 
Ore, Galena (Sulphide of Lead) should be available. This 
mineral occurs in many parts of New Zealand, and is not 
difficult to procure. 
Observe the general shape of the specimen and its dull 
gray surface. Scrape off some of the surface and notice the 
bluish-gray tint of the metal, its true colou r, and its bright 
metallic lustre. The gray film coating the surface is one 
of the Oxides of Lead, which has been formed by contact 
with the air. Ascertain that it is opaque, tough, and 
flexible. Notice its extreme softness compared with 
Tron. Lead is the softest of the common metals ; it can be 
readily cut with a knife and may even be scratched with 
the finger-nail. Hammer a piece of the metal on a hard 
surface and notice its malleability. Procure some lead 
wire and educe that it is ductile. Test for its tenacity 
by hanging a small weight to the end of the wire, which is 
easily broken. Contrast this property with that possessed 
by Iron, Copper, and other metals, by attaching first the 
same and then heavier weights to wire made of these 
metals. 
Determine its specific gravity and compare with that 
of Iron. Lead is the heaviest of all the common metals. 
Notice the absence of taste and the peculiar odour emitted 
when rubbed between the hands. 
Heat some of the metal in an iron spoon or ladle and 
notice how easily it melts—It is readily fusible. Observe 
that when first melted it presents a bright glistening 
