448 EXPERIMENT STATION RECORD. 



beat upon a field for a considerable length of time, it tends to injure the crops 

 severely and thus to diminish their yields. It tends to injure animals that are right 

 in the line of the prevailing winds, and therefore are compelled to breathe the 

 smelter smoke in the air. It may occasionally poison pools of standing water, when 

 the washing of rains and melting snows cause a concentration of the flue dust in low- 

 lying places ... It does not injure equally all land within any given radius. The 

 injured fields are those in the paths of the prevailing winds. It does not injure the 

 fertility of the soils of the district. It does not affect materially the feeding value of 

 crops grown in the district." 



Practical suggestions to farmers as to how to manage lands subject to injury by 

 smelter smoke are made. 



A new centrifugal soil elutriator, P. A. Yoder ( Utah Sta. Bui. 89, pp. 47, figs. 

 13). — This bulletin refers briefly to the more important methods and apparatus for 

 mechanical analysis which have been heretofore proposed, pointing out some of the 

 disadvantages which most of them possess, and describes an apparatus combining the 

 fundamental principles of the centrifugal and elutriator methods, which, it is claimed, 

 enables the analyst "to make a good separation in a comparatively short time, using 

 a relatively small volume of water, and securing at once each grade of particles 

 except the fine clay, in a minimum of water, ready for drying and weighing." 



In the apparatus described a special form of current elutriator is placed in suitable 

 sockets in a centrifugal machine, and carefully balanced by means of an adjustable 

 counterpoise. The muddy water resulting from the shaking up of a weighed sample 

 of soil is run in a uniform stream through the machine, and by regulating the 

 velocity of this stream or the rotary speed of the machine, it is possible to control 

 the grade of particles which are separated. 



A section of the centrifugal machine, with elutriator bottle and counterpoise in 

 position, is shown in figure 6. An enlarged section of the elutriator bottle is shown 

 in figure 7. This bottle is so designed as regards shape that a uniform force is 

 exerted oil the suspended soil particle in all parts of the bottle where separation 

 takes place. By making the outline of the bottle a parabolic curve, with the diam- 

 eter increasing as the axis of the machine is approached, it was found possible to 

 maintain a uniform ratio between centrifugal force and the force exerted by the 

 stream of water. 



The machine is found most useful for separating particles less than 0.03 mm. in 

 diameter, this fine material being most conveniently separated from the original 

 sample of soil by gravity elutriation. The elutriator bottle receives the water 

 containing the suspended soil through the funnel F, the axis of which coincides 

 with the axis of the centrifugal machine. From this funnel the water is carried to 

 the bottom of the bottle by means of a small tube. The overflow escapes through a 

 larger tube concentric with this smaller tube through the neck of the elutriator 

 bottle and is carried by a side tube T to a circular spray collector above. From 

 this collector a delivery tube drains the liquid into a beaker. 



The size of the particles which pass out of the machine suspended in water 

 depends both upon the velocity of the stream of water and upon the speed of the 

 machine. A uniform flow of the water containing the suspended soil particles is 

 secured by allowing the water to flow from a closed funnel-shaped vessel only as fast 

 as air is admitted from a larger closed bottle serving as an air chamber into which 

 water flows from the Mariotte bottle placed above through a valve which can be 

 regulated at will. 



By a series of experiments the relations between the speed of the machine and 

 the velocity of the current on the one hand and the size of the soil particles on the 

 other were carefully worked out. From the data obtained diagrams are plotted and 

 formulas are deduced for definitely determining these relations. 



In the actual operation of the machine 10 gm. of soil is thoroughly disintegrated 



