TIN LEAD. 191 



body called zinc. Bronze is composed of copper 

 and tin. Some care is required in using copper. 

 If acids or fruits are put into vessels of this metal, 

 they should be well cleaned afterwards, or a green 

 substance or salt is formed on them, which is 

 poisonous. For this reason many copper pans are 

 covered with tin. 



Tin, which belongs almost exclusively to Eng- 

 land, is found in great quantities in the mines of 

 Cornwall. It is an important article of commerce, 

 as the English supply nearly the whole world 

 with it. Many domestic utensils are made of it, 

 and when rolled into very thin leaves, called tin- 

 foil, it is used for covering sheets of iron, which 

 are then termed block-tin, from which cans and 

 many other things are made. Pewter is a compo- 

 sition of tin, lead, and brass; and many years ago 

 was extensively used for making dinner plates and 

 dishes. 



Lead, of which there are many rich mines in 

 Missouri, and also in England and Wales, is em- 

 ployed for spouts and water-pipes, and is rolled 

 into sheets for covering roofs. For this purpose 

 it is better fitted than many other metals, as it is 

 not liable to be so much injured by the air. Bul- 

 lets are cast from it in moulds ; and small shot is 

 now made by first melting a quantity, and then 

 pouring it into an iron vessel pierced with holes, 

 and placed at the top of a high building: from this 

 it is allowed to fall to the bottom into water, and 

 in its descent it assumes a round shape. 



