THE INDUSTRIAL TITAN OF AMERICA 



383 





A ROTARY CEMENT KILN 



The powdered coal is introduced into the kiln through the pipe in the end. The glowing 

 spot below is the opening through which, after having donned green goggles, one looks at 

 the inferno within. 



when they digest their quota of cement 

 rock that substance looks like flour that 

 has turned dark gray. 



While the rock crushers and grinders 

 are busy — whole batteries of them — the 

 coal crushers and grinders are at work 

 also, preparing coal dust as finely ground 

 and impalpable as the rock dust. 



THE ROTARY CEMENT KILN 



Here another process begins, in which 

 long rows of rotary kilns play an impor- 

 tant role. Imagine a hollow pipe, lined 

 with fire-brick, big enough for a horse 

 to walk through, about 150 feet long, 

 mounted on pivots and rotated by cog 

 gears after the fashion of a great shaft. 

 Into one end pours a constant stream of 

 rock dust. Into the other, driven madly 

 forward by compressed air, goes a like 

 stream of coal dust, hissing and burning, 

 as from an inferno. In the middle of the 

 big kiln they meet. 



The observer is supplied with a pair of 

 colored glasses ; the operator opens a tiny 



door and bids you look in. Glowing with 

 a whiteness that rivals the electric arc, 

 you see the materials apparently in the 

 process of turning from solid to liquid; 

 but, just at the point of incipient fusion, 

 droplets or nodules of a dark-gray color, 

 ranging from the size of a small pea to 

 that of a large hazelnut, are formed. 



These nodules are carried out on an 

 endless-bucket belt, glowing like embers 

 on a hearthstone, to the cooling towers. 

 Here they are cooled under forced 

 drafts of cold air. Then they go to meet 

 another set of grinders, to endure the 

 beatings of another series of mechanical 

 flails. Literally they are beaten to dust — 

 and that dust is the Portland cement of 

 commerce, to which the world's debt 

 cannot be estimated with any yardstick 

 at my command. 



THE SCIENCE OE HANDLING DUST 

 WITHOUT WASTE 



The finished product is carried to large 

 storage bins and then barreled or bagged. 



