TREATMENT WITHOUT FILLING 187 



a rather soft grade being best suited to tree work. 

 The most useful thickness is No. 9 zinc gauge, 

 which comes in sheets and rolls of various lengths 

 and costs not far from seventy-five cents a square 

 yard, retail. Heavier and lighter, as well as 

 harder, zincs have their uses. 



Galvanized iron is of course zinc-plated sheet 

 iron. It is heavier and stronger than sheet zinc 

 and is valuable for large flat work. No. 22, sheet 

 iron gauge, is a good weight. It comes in sheets 

 two feet by seven, which cost about two dollars. 



Soft sheet copper is a pleasant material to 

 handle and is a good material for covering wounds 

 where much bending and fitting is required. It 

 is the most permanent sheet metal, but is of course 

 not strong. It cannot often be substituted for 

 zinc on account of its high cost, the thickness 

 weighing ten ounces a square foot costing about a 

 dollar and a half a square yard. 



Tin-plated sheet iron (roofing tin) does fairly 

 well for small jobs where there is not much strain 

 and where It can be kept painted. The weight 

 stamped IC is the one oftenest used. 



Ordinary sheet iron, such as Is used for making 

 stove-pipes, is the cheapest sheet metal, but it 

 requires extraordinary precautions to prevent rust- 

 ing, and one is never quite sure of it. The nails 

 used are zincked shingle or basket nails, with 

 fairly large heads. 



