230 GEOLOGY OF OHIO 



The ''Steamer" consists of a tight wooden box, provided with two 

 small parallel pug mill shafts in the bottom. The clay is fed into it in a 

 stream, which is broken up into a shower by a high speed rotary wire 

 brush. The shower of clay falls through a zone where it passes between 

 jets of steam blowing in contrary directions, and falls to the bottom of 

 the box where the pug shafts keep it agitated in the steamy atmosphere 

 until it is ejected. 



Mr. Arnold claims great advantage for this arrangement in temper- 

 ing clay for a dry press machine; he asserts that the strength of the brick 

 are very materially increased, and the general quality of the ware greatly 

 improved. 



As a means of introducing evenly a small quantity of moisture into 

 the clay to be pressed, this machine is probably a valuable contribution 

 to the already existing forms of tempering machinery. 



The same effect is to some extent realized by wetting slightly the 

 clays as they are grinding in the dry pan. This is the wrong place to 

 add the water however, for it interferes both with grinding and screening 



The importance of this addition to the mechanical part of fire brick 

 manufacture cannot be properly defined. The quality of the material 

 has hardly been sufficiently demonstrated as yet, though in this one in- 

 stance the promises of permanent success are flattering. 



Dry pressed brick have certain advantages over all other kinds in the 

 particular field of usefulness which they are able to fill. They are first, 

 perfect in form and size, which is of great importance to the brick layers 

 in their work. Second, they are dense and strong, resisting more pres 

 sure under a crushing test than any other kind of brick. Third, they 

 cost less to manufacture than any other kind of brick. On the other 

 hand they will not resist severe abrasion, no matter how hard they are 

 burned, as they never develop any cohesive bond at all comparable with 

 that attained by the use of water. 



The structure of good fire brick has always been purposely made 

 very open and porous. The dry pressed brick cannot be called open in 

 any sense. It is an aggregation of particles brought into their relative 

 position by pressure and nothing else, and it is more dense and weighs 

 more to the cubic inch than any wet brick can be made to do. Neverthe- 

 less it is easily permeable to water and possibly to air and heat as well, 

 for it is impossible by pressure alone to force any particles into any close 

 union like that attained by water. 



The question of the value of the process hinges on this point. Is 

 the fine and minute porosity of a dry pressed brick a fair equivalent for 

 the coarser and more apparent porosity of the hand moulded article. If 

 it is, an intelligent and careful trial of the two kinds of material will prove 

 it to be so, and in that case, the use of dry press machinery in fire brick 

 manufacture is the most important and valuable addition to the resources 

 of the trade that has been made in the last twenty } 7 ears. 



