684 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



figure 55. The grounded electrodes are plates of heavy wire screen 

 reinforced by angle iron ribs, and the discharge electrodes are light 

 iron wires. 



Figure 56 shows the operating gallery running the whole length of 

 the row of treaters and containing the motor-generator sets, recti- 

 fiers, and transformers, together with their control sm itcliboards, as 

 well as the compressed-air valves governing the operating machinery 

 of the damper and the shaking devices for dislodging the dust from 

 the electrodes. This dust falls into hoppers, from whence it passes 

 by a system of screw conveyors and automatic scales to the storage 

 and car-loading bins. The whole installation requires but one oper- 

 ator, and the electrical-power consumption, including motor-gen- 

 erator and transformer losses, is about 35 kilowatts. The cost of the 

 installation Avas somewhat less than $200,000. As stated, it was in- 

 stalled purely to overcome the dust nuisance, and was not expected 

 to return any significant values, as the dust is not finished cement, 

 but chiefly raw mix carried out by the gases before it has reached 

 the clinkering zone. The raw mix used contains, however, a small 

 percentage of potash (usually not exceeding 1 per cent KoO), which 

 largely volatilizes and most of which is condensed and caught in solu- 

 ble form in the dust, making the latter, even in its crude form, as 

 collected, a fertilizing agent which finds a ready market at nearly 

 as good a price as the finished cement, or by using it over again in the 

 raw mix of a separate kiln a second and higher concentration of the 

 potash may be effected in the dust caught from this. 



We thus have another example of a plant, put in at a supposed loss 

 purely to avoid trouble with the neighbors, pro\ing not only to cover 

 its own operating exjDenses, but to actually pay a rather handsome 

 return on the very considerable investment involved. The plant has 

 been in uninterrupted operation on this basis since January 8, 1913. 

 As this article goes to press the first unit of similar character east 

 of the Mississippi is about to go into service, and in Europe another 

 is under construction. 



FURTHER DEVELOPMENT IN PROGRESS. 



A number of other installations, each with its features of special 

 interest, might also be referred to, but sufficient has been said to indi- 

 cate at least in outline the field developing before these processes. 



As early as 1907 Mr. Erwin Moller, son of Dr. Karl Moller, 

 already mentioned as one of the pioneers of electrical precipitation, 

 had independently taken up this work in Europe and is now cooper- 

 ating with the American investigators whose work is described above 

 in the further development of the subject, having also joined with 

 them in the assignment of patent rights to the research corporation 

 for the benefit of the Smithsonian Institution. 



