ROOFING 



247 



Corrugated steel roofing should be kept well painted with a good 

 paint. Where the roofing is exposed to the action of corrosive gases 

 as in the roof of a smelter reducing sulphur ores, ordinary red lead or 

 iron oxide paint is practically worthless as a protective coating; better 

 results being obtained with graphite and asphalt paints. Graphite paint 

 has been quite extensively used for painting corrugated steel in the 

 Butte, Mont., district. The corrosion of corrugated steel is sometimes 

 very rapid. In 1898 the author saw at the Trail Smelter, Trail, B. C., 

 a corrugated steel roof made of No. 22 corrugated steel and painted 

 with oxide of iron paint that had corroded so badly in one year that 

 one could stick his finger through it as easily as through brown paper. 

 The climate in that locality is moist and the smelter was used for re- 

 ducing sulphur ores. Galvanized corrugated steel is quite extensively 

 used in the Lake Superior district. 



Slate Roofing. There are many varieties of roofing slate, among 

 which the Brownville and Monson slates of Maine, and the Bangor 

 and Peach Bottom slates of Pennsylvania are well known and are of 



FIG. 130. 



excellent quality. Besides the characteristic slaty color, green, purple, 

 red and variegated roofing slates may be obtained. The best quality 

 of slate has a glistening semi-metallic appearance. Slate with a dull 



