Mance: Quarry Industry of Southern Indiana 147 



is fed to the ring-roll mill. This materially increases the output 

 of the plant. They range in capacity from 1 to 12 tons per hour 

 and cost from S429 up to S2,858. These machines can be used 

 on rock of a large size without previous crushing, but are 

 slower in action than a breaker. 



Ring-roll mills are made to handle outputs from the small 

 requirements of a laboratory up to those of large machines with 

 an output of 40 tons per hour, and costing up to $8,857. 



Vibrating screens cost from $400 to $600, according to the 

 fineness of the product desired. Their capacity approximates 

 6 tons per hour for limestone reduced to 20-mesh. 



The estimate of one of the leading firms on the cost of wear 

 and upkeep on the machinerj^ of a limestone crushing plant 

 is about one-third of a cent per ton for the material turned out. 

 This cost per ton is divided as follow^s: 



Crusher, including new plates and jaws 0.03 cent. 



Ring-roll mill 0 . 08 cent. 



Elevator 0.007 cent. 



Screens 0.05 cent. 



Amount for belts, etc 0 . 20 cent. 



Total cost 0 . 367 cent 



Since the average farmer would rather purchase a ready-- 

 mixed fertilizer than to trouble to mix it himself, it might be good 

 economy to construct a mixing plant in connection with a crushed 

 lim^estone plant in this district, and to that end the proposition 

 of getting raw rock phosphate was taken up with several of the 

 dealers in the phosphate belt of Tennessee, which is the nearest 

 available deposit of this raw material. The owners of these 

 deposits quoted prices averaging $6 to $6.50 per ton, laid down 

 in Bloomington in small lots, and these prices would probably 

 be reduced to at least $5 per ton on a large contract with a plant 

 which was handling a large part of their output. These figures 

 are on a phosphate rock that carries from 11 to 14 per cent phos- 

 phorous, or in other words represents about 25 per cent available 

 phosphoric acid. 



The proportion usually recommended for treatment of ordinary 

 soils is two parts of limestone to one of ground phosphate rock. 

 At this rate the mixture could be turned out ready for use at 

 about $2.25 per ton. Allowing a fair profit to the operator, it 

 could be sold f.o.b. Bloomington at about $3.50 per ton. This 

 would bring it to almost any part of the State at less than $5 per 



