THE ROOF AND FOUNDATION. 107 



conditions, and over a, considerable period of years. As a result 

 of the satisfactory experience, a great many types of metal 

 silos have been devised, from those riveted up like a railroad 

 water tank, various types of partly riveted and partly bolted 

 sections, to those of interchangeable sections with various types 

 of flanges. The type apparently most In favor, however, is 

 that first brought out. Numbers of metal silos are in use as irri- 

 gation water tanks during the summer when empty of silage. 



"Any question of the durability of metal silos has long since 

 been ■ completely answered by their continued use without appar- 

 ent defects, rust or corrosion of any kind. Their use is rapidly 

 growing in all sections of the country, East and West, and results 

 are everywhere perfectly satisfactory." , 



Manufacturers furnish metal silos In uniform sized sheets or 

 sections, finished complete ready tO' bolt into the silo. The 

 sheets are interchangeably matching and are about two feet 

 wide by 7% feet long. Different gauges of metal are used, some 

 having a strength of 45,000 pounds to the squa,re inch. Lighter 

 material is used toward the top in proportion to the diminishing? 

 pressure exerted by the silage. Appurtenances such as doors, 

 roofing sections, bar-iron, bolts, joint-cement, paint, etc., are 

 usually boxed or crated. 



Painting. — Metal silos should be painted once a year, long 

 enough before filling to set well. The reason for this is given 

 by one manufacturer as follows: 



"In the production of silage certain mild acids are formed 

 by fermentation, which, if no protection was offered would have 

 a tendency to cause the metal to corrode. To provide against 

 this, it is advisable to keep the inside of the silo painted with 

 some elastic, acid-resisting paint. Such paints are put up by 

 practically all of the best paint manufacturers. Any good paint, 

 with an asphaltum or gilsonite base, that is prepared so that 

 it will not dry too quickly, can be depended upon. We suggest 

 asphaltum or gilsonite, because such paints are thoroughly satis- 

 factory, and the cost is considerably less than that of some 

 other kinds." 



The Metal Silo Roof. — The roof adds greatly to the appear- 

 ance of the metal silo and prptects it against undue wind strain 

 or vibration. In northern climates it acts as a protection against 

 snow and freezing, and in warmer zones against the extreme 

 heat of the sun which would cause considerable loss between 

 feedings. It is an added expense, of course, and as rain Is not 

 injurious to silage the roof is considered superfluous in some 

 sections of the Southwest. The permanent roof also prevents 



