48 ANNUAL OF SCIENTIFIC DISCOVERY. 



Tlio broken fraq'mcnts ai"e swept tlirou£;:li tlie holes or f^^ratin^^ 

 of the tub the instant they arc proclucetl, by the immediate aetioii 

 of the advanoinf^ faces of the cutting lilades. Thus it liappens 

 that no part of the work of reduction is performed l)j the sides of 

 the tub, but solely by the l)lades. The ta1)le is maile strong 

 enough to bear 1,500 revolutions jier minute, without rupture; 

 but any speed above 1,02.> turns per minute is wasteful of steam 

 power, and does not nnieh increase the yield. 



In general, the higher the velocity of the whirling-table, the 

 less it wears, according to tlie amount of work done. 



The whirling-table is intended to reduce oi-es, from a diameter 

 from three to six inches, to the condition of mixed sand and small 

 gravel, cliielly tlic latter, with a small i)crcentage of (kist. 



Tlie pulverizer is constructed solely for the; pulverization or re- 

 duction to dust of sand, gravel, or the small work of stamping 

 machines, and cannot he used itself as a crusher or breaker. It 

 consists of four parts or elements, all of wliich are necessary to 

 its use. Tlic lirst is an automatic feeding-mill, wliich furnishes a 

 regular and constant supply of the material to be pulverized. 



The second element is an iron drum or cylinder, containing an 

 air-wheel, which converts the sand or gravi-l into dust by the 

 action of rotary ciu'rents of air, created by the wheel. No air 

 enters or escapes from this cylinder, unless by the aid of other 

 machinery. The material can be retained in the cylinder imtil 

 it is completely reduced. 



The third element is a fan-blower, — placed near, or at a con- 

 siderable distance Irom, the liulverizing cylintler, — by which the 

 dust is drawn from the lattm* as fast as it is generatcid. The 

 gravel, sand, auriiVrous earth, or other material, is pulverized in 

 the first cj-linder by the action of currents of air generated I)y 

 the air-wheel ; the dust is then drawn out, in company with air, 

 by the exhaustive force of the fan-blower. The fourth element is 

 a chamber, or series of chambers, to receive and collect tlu; dust 

 generated by the pulverizer. The dust-chambers are variously 

 constructed to suit the nature of the material which is to be re- 

 duced, and are adapted either for dr}^ or wet grinding, as may ]je 

 I'cquired. A single liulverizer, applied to the reduction of gold 

 ores, accomplishes with a smaller consumiMion of steam or water 

 power, the work of forty stamps, and the quality of the work pro- 

 duced is beyond all comparison finer. In a pulverizer theoreti- 

 cally perfect, the principle of its working is the movement of one 

 particle on another, or mutual attrition, promoted by vortices of 

 air. 



Three pulverizers vnll give the work, in quantity, of ninety 

 stamps ; and the quality of this work will be so much superior 

 that the miner may safely estimate his profits at twenty dollars 

 per ton, instead of ten dollai-s, from quartz assaying thirty dollars. 



In ordinary practice, but one element of an ore — that of most 

 prominent value — is sought for ; the other elements being re- 

 jected in slags or escaping in fumes from the furnaces. Refei*- 

 ence may be had to the loss of iron and sulphur from coj^per ores ; 

 the loss of copper, iron, and sulphur in worldng nickel ores and 



